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openGauss-server/contrib/postgres_fdw/postgres_fdw.cpp
g30037312 980e75155a flatten expr framework
2023-03-12 19:16:08 -07:00

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/* -------------------------------------------------------------------------
*
* postgres_fdw.c
* Foreign-data wrapper for remote openGauss servers
*
* Portions Copyright (c) 2020 Huawei Technologies Co.,Ltd.
* Portions Copyright (c) 2012-2014, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/postgres_fdw.c
*
* -------------------------------------------------------------------------
*/
#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup.h"
#include "access/sysattr.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "knl/knl_guc.h"
#include "access/tableam.h"
#include "internal_interface.h"
PG_MODULE_MAGIC;
/* Default CPU cost to start up a foreign query. */
#define DEFAULT_FDW_STARTUP_COST 100.0
/* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */
#define DEFAULT_FDW_TUPLE_COST 0.01
/* If no remote estimates, assume a sort costs 20% extra */
#define DEFAULT_FDW_SORT_MULTIPLIER 1.2
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
* We store various information in ForeignScan.fdw_private to pass it from
* planner to executor. Currently we store:
*
* 1) SELECT statement text to be sent to the remote server
* 2) Integer list of attribute numbers retrieved by the SELECT
*
* These items are indexed with the enum FdwScanPrivateIndex, so an item
* can be fetched with list_nth(). For example, to get the SELECT
* statement: sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql))
*/
enum FdwScanPrivateIndex {
/* SQL statement to execute remotely (as a String node) */
FdwScanPrivateSelectSql,
/* Integer list of attribute numbers retrieved by the SELECT */
FdwScanPrivateRetrievedAttrs,
/* Integer representing the desired fetch_size */
FdwScanPrivateFetchSize,
/*
* String describing join i.e. names of relations being joined and types
* of join, added when the scan is join
*/
FdwScanPrivateRelations
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ModifyTable node referencing a postgres_fdw foreign table. We store:
*
* 1) INSERT/UPDATE/DELETE statement text to be sent to the remote server
* 2) Integer list of target attribute numbers for INSERT/UPDATE
* (NIL for a DELETE)
* 3) Boolean flag showing if the remote query has a RETURNING clause
* 4) Integer list of attribute numbers retrieved by RETURNING, if any
*/
enum FdwModifyPrivateIndex {
/* SQL statement to execute remotely (as a String node) */
FdwModifyPrivateUpdateSql,
/* Integer list of target attribute numbers for INSERT/UPDATE */
FdwModifyPrivateTargetAttnums,
/* has-returning flag (as an integer Value node) */
FdwModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwModifyPrivateRetrievedAttrs
};
/*
* Execution state of a foreign scan using postgres_fdw.
*/
typedef struct PgFdwScanState {
Relation rel; /* relcache entry for the foreign table */
TupleDesc tupdesc; /* tuple descriptor of scan */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* extracted fdw_private data */
char *query; /* text of SELECT command */
List *retrieved_attrs; /* list of retrieved attribute numbers */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
unsigned int cursor_number; /* quasi-unique ID for my cursor */
bool cursor_exists; /* have we created the cursor? */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
HeapTuple *tuples; /* array of currently-retrieved tuples */
int num_tuples; /* # of tuples in array */
int next_tuple; /* index of next one to return */
/* batch-level state, for optimizing rewinds and avoiding useless fetch */
int fetch_ct_2; /* Min(# of fetches done, 2) */
bool eof_reached; /* true if last fetch reached EOF */
/* working memory contexts */
MemoryContext batch_cxt; /* context holding current batch of tuples */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
int fetch_size; /* number of tuples per fetch */
} PgFdwScanState;
/*
* Execution state of a foreign insert/update/delete operation.
*/
typedef struct PgFdwModifyState {
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
char *p_name; /* name of prepared statement, if created */
/* extracted fdw_private data */
char *query; /* text of INSERT/UPDATE/DELETE command */
List *target_attrs; /* list of target attribute numbers */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
/* info about parameters for prepared statement */
AttrNumber ctidAttno; /* attnum of input resjunk ctid column */
AttrNumber tboidAttno; /* attnum of input resjunk tableoid column */
int p_nums; /* number of parameters to transmit */
FmgrInfo *p_flinfo; /* output conversion functions for them */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwModifyState;
/*
* Workspace for analyzing a foreign table.
*/
typedef struct PgFdwAnalyzeState {
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
List *retrieved_attrs; /* attr numbers retrieved by query */
/* collected sample rows */
HeapTuple *rows; /* array of size targrows */
int targrows; /* target # of sample rows */
int numrows; /* # of sample rows collected */
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
double rstate; /* random state */
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwAnalyzeState;
/*
* This enum describes what's kept in the fdw_private list for a ForeignPath.
* We store:
*
* 1) Boolean flag showing if the remote query has the final sort
* 2) Boolean flag showing if the remote query has the LIMIT clause
*/
enum FdwPathPrivateIndex {
/* has-final-sort flag (as a Boolean node) */
FdwPathPrivateHasFinalSort,
/* has-limit flag (as a Boolean node) */
FdwPathPrivateHasLimit
};
/* Struct for extra information passed to estimate_path_cost_size() */
typedef struct {
List *target;
bool has_final_sort;
bool has_limit;
double limit_tuples;
int64 count_est;
int64 offset_est;
} PgFdwPathExtraData;
/*
* Identify the attribute where data conversion fails.
*/
typedef struct ConversionLocation {
Relation rel; /* foreign table's relcache entry */
AttrNumber cur_attno; /* attribute number being processed, or 0 */
ForeignScanState *fsstate; /* plan node being processed, or NULL */
} ConversionLocation;
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(postgres_fdw_handler);
extern "C" Datum postgres_fdw_handler(PG_FUNCTION_ARGS);
/*
* FDW callback routines
*/
static void postgresGetForeignRelSize(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid);
static void postgresGetForeignPaths(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid);
static ForeignScan *postgresGetForeignPlan(PlannerInfo *root, RelOptInfo *foreignrel, Oid foreigntableid,
ForeignPath *best_path, List *tlist, List *scan_clauses, Plan *outer_plan);
static void postgresBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node);
static void postgresReScanForeignScan(ForeignScanState *node);
static void postgresEndForeignScan(ForeignScanState *node);
static void postgresAddForeignUpdateTargets(Query *parsetree, RangeTblEntry *target_rte, Relation target_relation);
static List *postgresPlanForeignModify(PlannerInfo *root, ModifyTable *plan, Index resultRelation, int subplan_index);
static void postgresBeginForeignModify(ModifyTableState *mtstate, ResultRelInfo *resultRelInfo, List *fdw_private,
int subplan_index, int eflags);
static TupleTableSlot *postgresExecForeignInsert(EState *estate, ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignUpdate(EState *estate, ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignDelete(EState *estate, ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void postgresEndForeignModify(EState *estate, ResultRelInfo *resultRelInfo);
static int postgresIsForeignRelUpdatable(Relation rel);
static void postgresExplainForeignScan(ForeignScanState *node, ExplainState *es);
static void postgresExplainForeignModify(ModifyTableState *mtstate, ResultRelInfo *rinfo, List *fdw_private,
int subplan_index, ExplainState *es);
static void postgresExplainForeignScanRemote(ForeignScanState *node, ExplainState *es);
static bool postgresAnalyzeForeignTable(Relation relation, AcquireSampleRowsFunc *func, BlockNumber *totalpages,
void *additionalData, bool estimate_table_rownum);
static void postgresGetForeignJoinPaths(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *outerrel,
RelOptInfo *innerrel, JoinType jointype, SpecialJoinInfo *sjinfo, List *restrictlist);
static void _postgresGetForeignUpperPaths(FDWUpperRelCxt *ufdw_cxt, UpperRelationKind stage);
static void postgresGetForeignUpperPaths(FDWUpperRelCxt* ufdwCxt, UpperRelationKind stage, Plan* mainPlan);
/*
* Helper functions
*/
static void estimate_path_cost_size(PlannerInfo *root, RelOptInfo *foreignrel, List *param_join_conds, List *pathkeys,
PgFdwPathExtraData *fpextra, double *p_rows, int *p_width, Cost *p_startup_cost, Cost *p_total_cost);
static void get_remote_estimate(const char *sql, PGconn *conn, double *rows, int *width, Cost *startup_cost,
Cost *total_cost);
static void create_cursor(ForeignScanState *node);
static void fetch_more_data(ForeignScanState *node);
static void close_cursor(PGconn *conn, unsigned int cursor_number);
static PgFdwModifyState *createForeignModify(EState *estate, RangeTblEntry *rte, ResultRelInfo *resultRelInfo,
CmdType operation, Plan *subplan, char *query, List *target_attrs, bool has_returning, List *retrieved_attrs);
static void prepare_foreign_modify(PgFdwModifyState *fmstate);
static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate, ItemPointer tupleid, ItemPointer tableid,
TupleTableSlot *slot);
static void store_returning_result(PgFdwModifyState *fmstate, TupleTableSlot *slot, PGresult *res);
static int postgresAcquireSampleRowsFunc(Relation relation, int elevel, HeapTuple *rows, int targrows,
double *totalrows, double *totaldeadrows, void *additionalData, bool estimate_table_rownum);
static void analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate);
static HeapTuple make_tuple_from_result_row(PGresult *res, int row, Relation rel, AttInMetadata *attinmeta,
List *retrieved_attrs, ForeignScanState *fsstate, MemoryContext temp_context);
static void conversion_error_callback(void *arg);
static void add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel, Path *epq_path);
static void apply_server_options(PgFdwRelationInfo *fpinfo);
static void apply_table_options(PgFdwRelationInfo *fpinfo);
static void merge_fdw_options(PgFdwRelationInfo *fpinfo, const PgFdwRelationInfo *fpinfo_o,
const PgFdwRelationInfo *fpinfo_i);
static void prepare_query_params(PlanState *node, List *fdw_exprs, int numParams, FmgrInfo **param_flinfo,
List **param_exprs, const char ***param_values);
static void add_foreign_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel, RelOptInfo *grouped_rel,
GroupPathExtraData *extra);
static void add_foreign_ordered_paths(PlannerInfo *root, RelOptInfo *input_rel, RelOptInfo *ordered_rel,
OrderPathExtraData *extra);
static void add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel, RelOptInfo *final_rel,
FinalPathExtraData *extra);
static void adjust_foreign_grouping_path_cost(PlannerInfo *root, List *pathkeys, double retrieved_rows, double width,
double limit_tuples, Cost *p_startup_cost, Cost *p_run_cost);
static void process_query_params(ExprContext *econtext, FmgrInfo *param_flinfo, List *param_exprs,
const char **param_values);
/*
* Foreign-data wrapper handler function: return a struct with pointers
* to my callback routines.
*/
Datum postgres_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *routine = makeNode(FdwRoutine);
/* Functions for scanning foreign tables */
routine->GetForeignRelSize = postgresGetForeignRelSize;
routine->GetForeignPaths = postgresGetForeignPaths;
routine->GetForeignPlan = postgresGetForeignPlan;
routine->BeginForeignScan = postgresBeginForeignScan;
routine->IterateForeignScan = postgresIterateForeignScan;
routine->ReScanForeignScan = postgresReScanForeignScan;
routine->EndForeignScan = postgresEndForeignScan;
/* Functions for updating foreign tables */
routine->AddForeignUpdateTargets = postgresAddForeignUpdateTargets;
routine->PlanForeignModify = postgresPlanForeignModify;
routine->BeginForeignModify = postgresBeginForeignModify;
routine->ExecForeignInsert = postgresExecForeignInsert;
routine->ExecForeignUpdate = postgresExecForeignUpdate;
routine->ExecForeignDelete = postgresExecForeignDelete;
routine->EndForeignModify = postgresEndForeignModify;
routine->IsForeignRelUpdatable = postgresIsForeignRelUpdatable;
/* Support functions for EXPLAIN */
routine->ExplainForeignScan = postgresExplainForeignScan;
routine->ExplainForeignModify = postgresExplainForeignModify;
routine->ExplainForeignScanRemote = postgresExplainForeignScanRemote;
/* Support functions for ANALYZE */
routine->AnalyzeForeignTable = postgresAnalyzeForeignTable;
routine->AcquireSampleRows = postgresAcquireSampleRowsFunc;
/* Support functions for join push-down */
routine->GetForeignJoinPaths = postgresGetForeignJoinPaths;
/* Support functions for upper relation push-down */
routine->GetForeignUpperPaths = postgresGetForeignUpperPaths;
PG_RETURN_POINTER(routine);
}
/*
* postgresGetForeignRelSize
* Estimate # of rows and width of the result of the scan
*
* We should consider the effect of all baserestrictinfo clauses here, but
* not any join clauses.
*/
static void postgresGetForeignRelSize(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid)
{
ListCell *lc = NULL;
/*
* We use PgFdwRelationInfo to pass various information to subsequent
* functions.
*/
PgFdwRelationInfo* fpinfo = (PgFdwRelationInfo *)palloc0(sizeof(PgFdwRelationInfo));
baserel->fdw_private = (void *)fpinfo;
/* Base foreign tables need to be pushed down always. */
fpinfo->pushdown_safe = true;
/* Look up foreign-table catalog info. */
fpinfo->table = GetForeignTable(foreigntableid);
fpinfo->server = GetForeignServer(fpinfo->table->serverid);
/*
* Extract user-settable option values. Note that per-table setting of
* use_remote_estimate overrides per-server setting.
*/
fpinfo->use_remote_estimate = false;
fpinfo->fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
fpinfo->fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
fpinfo->shippable_extensions = NIL;
fpinfo->fetch_size = 100;
fpinfo->async_capable = false;
apply_server_options(fpinfo);
apply_table_options(fpinfo);
/*
* If the table or the server is configured to use remote estimates,
* identify which user to do remote access as during planning. This
* should match what ExecCheckRTEPerms() does. If we fail due to lack of
* permissions, the query would have failed at runtime anyway.
*/
if (fpinfo->use_remote_estimate) {
RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
Oid userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
fpinfo->user = GetUserMapping(userid, fpinfo->server->serverid);
} else {
fpinfo->user = NULL;
}
/*
* Identify which baserestrictinfo clauses can be sent to the remote
* server and which can't.
*/
classifyConditions(root, baserel, baserel->baserestrictinfo, &fpinfo->remote_conds, &fpinfo->local_conds);
/*
* Identify which attributes will need to be retrieved from the remote
* server. These include all attrs needed for joins or final output, plus
* all attrs used in the local_conds. (Note: if we end up using a
* parameterized scan, it's possible that some of the join clauses will be
* sent to the remote and thus we wouldn't really need to retrieve the
* columns used in them. Doesn't seem worth detecting that case though.)
*/
fpinfo->attrs_used = NULL;
pull_varattnos((Node *)baserel->reltarget->exprs, baserel->relid, &fpinfo->attrs_used);
foreach (lc, fpinfo->local_conds) {
RestrictInfo *rinfo = (RestrictInfo *)lfirst(lc);
pull_varattnos((Node *)rinfo->clause, baserel->relid, &fpinfo->attrs_used);
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root, fpinfo->local_conds, baserel->relid, JOIN_INNER, NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction clauses, as well as the
* average row width. Otherwise, estimate using whatever statistics we
* have locally, in a way similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate) {
/*
* Get cost/size estimates with help of remote server. Save the
* values in fpinfo so we don't need to do it again to generate the
* basic foreign path.
*/
estimate_path_cost_size(root, baserel, NIL, NIL, NULL, &fpinfo->rows, &fpinfo->width, &fpinfo->startup_cost,
&fpinfo->total_cost);
/* Report estimated baserel size to planner. */
baserel->rows = fpinfo->rows;
baserel->reltarget->width = fpinfo->width;
} else {
/*
* If the foreign table has never been ANALYZEd, it will have relpages
* and reltuples equal to zero, which most likely has nothing to do
* with reality. We can't do a whole lot about that if we're not
* allowed to consult the remote server, but we can use a hack similar
* to plancat.c's treatment of empty relations: use a minimum size
* estimate of 10 pages, and divide by the column-datatype-based width
* estimate to get the corresponding number of tuples.
*/
if (baserel->pages == 0 && baserel->tuples == 0) {
baserel->pages = 10;
baserel->tuples = (double)(10 * BLCKSZ) / (baserel->reltarget->width + sizeof(HeapTupleHeaderData));
}
/* Estimate baserel size as best we can with local statistics. */
set_baserel_size_estimates(root, baserel);
/* Fill in basically-bogus cost estimates for use later. */
estimate_path_cost_size(root, baserel, NIL, NIL, NULL, &fpinfo->rows, &fpinfo->width, &fpinfo->startup_cost,
&fpinfo->total_cost);
}
/*
* fpinfo->relation_name gets the numeric rangetable index of the foreign
* table RTE. (If this query gets EXPLAIN'd, we'll convert that to a
* human-readable string at that time.)
*/
fpinfo->relation_name = psprintf("%u", baserel->relid);
/* No outer and inner relations. */
fpinfo->make_outerrel_subquery = false;
fpinfo->make_innerrel_subquery = false;
fpinfo->lower_subquery_rels = NULL;
/* Set the relation index. */
fpinfo->relation_index = baserel->relid;
}
/*
* get_useful_ecs_for_relation
* Determine which EquivalenceClasses might be involved in useful
* orderings of this relation.
*
* This function is in some respects a mirror image of the core function
* pathkeys_useful_for_merging: for a regular table, we know what indexes
* we have and want to test whether any of them are useful. For a foreign
* table, we don't know what indexes are present on the remote side but
* want to speculate about which ones we'd like to use if they existed.
*
* This function returns a list of potentially-useful equivalence classes,
* but it does not guarantee that an EquivalenceMember exists which contains
* Vars only from the given relation. For example, given ft1 JOIN t1 ON
* ft1.x + t1.x = 0, this function will say that the equivalence class
* containing ft1.x + t1.x is potentially useful. Supposing ft1 is remote and
* t1 is local (or on a different server), it will turn out that no useful
* ORDER BY clause can be generated. It's not our job to figure that out
* here; we're only interested in identifying relevant ECs.
*/
static List *get_useful_ecs_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
List *useful_eclass_list = NIL;
ListCell *lc = NULL;
Relids relids;
/*
* First, consider whether any active EC is potentially useful for a merge
* join against this relation.
*/
if (rel->has_eclass_joins) {
foreach (lc, root->eq_classes) {
EquivalenceClass *cur_ec = (EquivalenceClass *)lfirst(lc);
if (eclass_useful_for_merging(cur_ec, rel))
useful_eclass_list = lappend(useful_eclass_list, cur_ec);
}
}
/*
* Next, consider whether there are any non-EC derivable join clauses that
* are merge-joinable. If the joininfo list is empty, we can exit
* quickly.
*/
if (rel->joininfo == NIL) {
return useful_eclass_list;
}
relids = rel->relids;
/* Check each join clause in turn. */
foreach (lc, rel->joininfo) {
RestrictInfo *restrictinfo = (RestrictInfo *)lfirst(lc);
/* Consider only mergejoinable clauses */
if (restrictinfo->mergeopfamilies == NIL) {
continue;
}
/* Make sure we've got canonical ECs. */
update_mergeclause_eclasses(root, restrictinfo);
/*
* restrictinfo->mergeopfamilies != NIL is sufficient to guarantee
* that left_ec and right_ec will be initialized, per comments in
* distribute_qual_to_rels.
*
* We want to identify which side of this merge-joinable clause
* contains columns from the relation produced by this RelOptInfo. We
* test for overlap, not containment, because there could be extra
* relations on either side. For example, suppose we've got something
* like ((A JOIN B ON A.x = B.x) JOIN C ON A.y = C.y) LEFT JOIN D ON
* A.y = D.y. The input rel might be the joinrel between A and B, and
* we'll consider the join clause A.y = D.y. relids contains a
* relation not involved in the join class (B) and the equivalence
* class for the left-hand side of the clause contains a relation not
* involved in the input rel (C). Despite the fact that we have only
* overlap and not containment in either direction, A.y is potentially
* useful as a sort column.
*
* Note that it's even possible that relids overlaps neither side of
* the join clause. For example, consider A LEFT JOIN B ON A.x = B.x
* AND A.x = 1. The clause A.x = 1 will appear in B's joininfo list,
* but overlaps neither side of B. In that case, we just skip this
* join clause, since it doesn't suggest a useful sort order for this
* relation.
*/
if (bms_overlap(relids, restrictinfo->right_ec->ec_relids)) {
useful_eclass_list = list_append_unique_ptr(useful_eclass_list, restrictinfo->right_ec);
} else if (bms_overlap(relids, restrictinfo->left_ec->ec_relids)) {
useful_eclass_list = list_append_unique_ptr(useful_eclass_list, restrictinfo->left_ec);
}
}
return useful_eclass_list;
}
/*
* get_useful_pathkeys_for_relation
* Determine which orderings of a relation might be useful.
*
* Getting data in sorted order can be useful either because the requested
* order matches the final output ordering for the overall query we're
* planning, or because it enables an efficient merge join. Here, we try
* to figure out which pathkeys to consider.
*/
static List *get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
List *useful_pathkeys_list = NIL;
List *useful_eclass_list = NIL;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)rel->fdw_private;
EquivalenceClass *query_ec = NULL;
ListCell *lc = NULL;
/*
* Pushing the query_pathkeys to the remote server is always worth
* considering, because it might let us avoid a local sort.
*/
fpinfo->qp_is_pushdown_safe = false;
if (root->query_pathkeys) {
bool query_pathkeys_ok = true;
foreach (lc, root->query_pathkeys) {
PathKey *pathkey = (PathKey *)lfirst(lc);
/*
* The planner and executor don't have any clever strategy for
* taking data sorted by a prefix of the query's pathkeys and
* getting it to be sorted by all of those pathkeys. We'll just
* end up resorting the entire data set. So, unless we can push
* down all of the query pathkeys, forget it.
*/
if (!is_foreign_pathkey(root, rel, pathkey)) {
query_pathkeys_ok = false;
break;
}
}
if (query_pathkeys_ok) {
useful_pathkeys_list = list_make1(list_copy(root->query_pathkeys));
fpinfo->qp_is_pushdown_safe = true;
}
}
/*
* Even if we're not using remote estimates, having the remote side do the
* sort generally won't be any worse than doing it locally, and it might
* be much better if the remote side can generate data in the right order
* without needing a sort at all. However, what we're going to do next is
* try to generate pathkeys that seem promising for possible merge joins,
* and that's more speculative. A wrong choice might hurt quite a bit, so
* bail out if we can't use remote estimates.
*/
if (!fpinfo->use_remote_estimate) {
return useful_pathkeys_list;
}
/* Get the list of interesting EquivalenceClasses. */
useful_eclass_list = get_useful_ecs_for_relation(root, rel);
/* Extract unique EC for query, if any, so we don't consider it again. */
if (list_length(root->query_pathkeys) == 1) {
PathKey *query_pathkey = (PathKey *)linitial(root->query_pathkeys);
query_ec = query_pathkey->pk_eclass;
}
/*
* As a heuristic, the only pathkeys we consider here are those of length
* one. It's surely possible to consider more, but since each one we
* choose to consider will generate a round-trip to the remote side, we
* need to be a bit cautious here. It would sure be nice to have a local
* cache of information about remote index definitions...
*/
foreach (lc, useful_eclass_list) {
EquivalenceClass *cur_ec = (EquivalenceClass *)lfirst(lc);
PathKey *pathkey = NULL;
/* If redundant with what we did above, skip it. */
if (cur_ec == query_ec) {
continue;
}
/* Can't push down the sort if the EC's opfamily is not shippable. */
if (!is_builtin(linitial_oid(cur_ec->ec_opfamilies))) {
continue;
}
/* If no pushable expression for this rel, skip it. */
if (find_em_for_rel(root, cur_ec, rel) == NULL) {
continue;
}
/* Looks like we can generate a pathkey, so let's do it. */
pathkey =
make_canonical_pathkey(root, cur_ec, linitial_oid(cur_ec->ec_opfamilies), BTLessStrategyNumber, false);
useful_pathkeys_list = lappend(useful_pathkeys_list, list_make1(pathkey));
}
return useful_pathkeys_list;
}
/*
* postgresGetForeignPaths
* Create possible scan paths for a scan on the foreign table
*/
static void postgresGetForeignPaths(PlannerInfo *root, RelOptInfo *baserel, Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)baserel->fdw_private;
ListCell *lc = NULL;
/*
* Create simplest ForeignScan path node and add it to baserel. This path
* corresponds to SeqScan path of regular tables (though depending on what
* baserestrict conditions we were able to send to remote, there might
* actually be an indexscan happening there). We already did all the work
* to estimate cost and size of this path.
*
* Although this path uses no join clauses, it could still have required
* parameterization due to LATERAL refs in its tlist.
*/
ForeignPath* path = create_foreignscan_path(root, baserel,
fpinfo->startup_cost, fpinfo->total_cost, NIL, /* no pathkeys */
NULL, NULL, NIL); /* no fdw_private list */
add_path(root, baserel, (Path *)path);
/* Add paths with pathkeys */
add_paths_with_pathkeys_for_rel(root, baserel, NULL);
/*
* If we're not using remote estimates, stop here. We have no way to
* estimate whether any join clauses would be worth sending across, so
* don't bother building parameterized paths.
*/
if (!fpinfo->use_remote_estimate) {
return;
}
/*
* Thumb through all join clauses for the rel to identify which outer
* relations could supply one or more safe-to-send-to-remote join clauses.
* We'll build a parameterized path for each such outer relation.
*
* It's convenient to manage this by representing each candidate outer
* relation by the ParamPathInfo node for it. We can then use the
* ppi_clauses list in the ParamPathInfo node directly as a list of the
* interesting join clauses for that rel. This takes care of the
* possibility that there are multiple safe join clauses for such a rel,
* and also ensures that we account for unsafe join clauses that we'll
* still have to enforce locally (since the parameterized-path machinery
* insists that we handle all movable clauses).
*/
List *ppi_list = NIL;
foreach (lc, baserel->joininfo) {
RestrictInfo *rinfo = (RestrictInfo *)lfirst(lc);
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel->relid)) {
continue;
}
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause)) {
continue;
}
/* Calculate required outer rels for the resulting path */
Relids required_outer = bms_union(rinfo->clause_relids, NULL);
/* We do not want the foreign rel itself listed in required_outer */
required_outer = bms_del_member(required_outer, baserel->relid);
/*
* required_outer probably can't be empty here, but if it were, we
* couldn't make a parameterized path.
*/
if (bms_is_empty(required_outer)) {
continue;
}
/* Get the ParamPathInfo */
ParamPathInfo* param_info = get_baserel_parampathinfo(root, baserel, required_outer);
Assert(param_info != NULL);
/*
* Add it to list unless we already have it. Testing pointer equality
* is OK since get_baserel_parampathinfo won't make duplicates.
*/
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/*
* Now build a path for each useful outer relation.
*/
foreach (lc, ppi_list) {
ParamPathInfo *param_info = (ParamPathInfo *)lfirst(lc);
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Get a cost estimate from the remote */
estimate_path_cost_size(root, baserel, param_info->ppi_clauses, NIL, NULL, &rows, &width, &startup_cost, &total_cost);
/*
* ppi_rows currently won't get looked at by anything, but still we
* may as well ensure that it matches our idea of the rowcount.
*/
param_info->ppi_rows = rows;
/* Make the path */
path = create_foreignscan_path(root, baserel,
startup_cost, total_cost, NIL, /* no pathkeys */
param_info->ppi_req_outer, NULL, NIL); /* no fdw_private list */
add_path(root, baserel, (Path *)path);
}
}
/*
* postgresGetForeignPlan
* Create ForeignScan plan node which implements selected best path
*/
static ForeignScan *postgresGetForeignPlan(PlannerInfo *root, RelOptInfo *foreignrel, Oid foreigntableid,
ForeignPath *best_path, List *tlist, List *scan_clauses, Plan *outer_plan)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)foreignrel->fdw_private;
Index scan_relid;
List *fdw_private = NIL;
List *remote_exprs = NIL;
List *local_exprs = NIL;
List *params_list = NIL;
List *fdw_scan_tlist = NIL;
List *fdw_recheck_quals = NIL;
List *retrieved_attrs = NIL;
StringInfoData sql;
bool has_final_sort = false;
bool has_limit = false;
ListCell *lc = NULL;
/*
* Get FDW private data created by postgresGetForeignUpperPaths(), if any.
*/
if (best_path->fdw_private) {
has_final_sort = boolVal(list_nth(best_path->fdw_private, FdwPathPrivateHasFinalSort));
has_limit = boolVal(list_nth(best_path->fdw_private, FdwPathPrivateHasLimit));
}
if (IS_SIMPLE_REL(foreignrel)) {
/*
* For base relations, set scan_relid as the relid of the relation.
*/
scan_relid = foreignrel->relid;
/*
* In a base-relation scan, we must apply the given scan_clauses.
*
* Separate the scan_clauses into those that can be executed remotely
* and those that can't. baserestrictinfo clauses that were
* previously determined to be safe or unsafe by classifyConditions
* are found in fpinfo->remote_conds and fpinfo->local_conds. Anything
* else in the scan_clauses list will be a join clause, which we have
* to check for remote-safety.
*
* Note: the join clauses we see here should be the exact same ones
* previously examined by postgresGetForeignPaths. Possibly it'd be
* worth passing forward the classification work done then, rather
* than repeating it here.
*
* This code must match "extract_actual_clauses(scan_clauses, false)"
* except for the additional decision about remote versus local
* execution.
*/
foreach (lc, scan_clauses) {
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
/* Ignore any pseudoconstants, they're dealt with elsewhere */
if (rinfo->pseudoconstant) {
continue;
}
if (list_member_ptr(fpinfo->remote_conds, rinfo)) {
remote_exprs = lappend(remote_exprs, rinfo->clause);
} else if (list_member_ptr(fpinfo->local_conds, rinfo)) {
local_exprs = lappend(local_exprs, rinfo->clause);
} else if (is_foreign_expr(root, foreignrel, rinfo->clause)) {
remote_exprs = lappend(remote_exprs, rinfo->clause);
} else {
local_exprs = lappend(local_exprs, rinfo->clause);
}
}
/*
* For a base-relation scan, we have to support EPQ recheck, which
* should recheck all the remote quals.
*/
fdw_recheck_quals = remote_exprs;
} else {
/*
* Join relation or upper relation - set scan_relid to 0.
*/
scan_relid = 0;
/*
* For a join rel, baserestrictinfo is NIL and we are not considering
* parameterization right now, so there should be no scan_clauses for
* a joinrel or an upper rel either.
*/
Assert(!scan_clauses);
/*
* Instead we get the conditions to apply from the fdw_private
* structure.
*/
remote_exprs = extract_actual_clauses(fpinfo->remote_conds, false);
local_exprs = extract_actual_clauses(fpinfo->local_conds, false);
/*
* We leave fdw_recheck_quals empty in this case, since we never need
* to apply EPQ recheck clauses. In the case of a joinrel, EPQ
* recheck is handled elsewhere --- see postgresGetForeignJoinPaths().
* If we're planning an upperrel (ie, remote grouping or aggregation)
* then there's no EPQ to do because SELECT FOR UPDATE wouldn't be
* allowed, and indeed we *can't* put the remote clauses into
* fdw_recheck_quals because the unaggregated Vars won't be available
* locally.
*/
/* Build the list of columns to be fetched from the foreign server. */
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
/*
* Ensure that the outer plan produces a tuple whose descriptor
* matches our scan tuple slot. Also, remove the local conditions
* from outer plan's quals, lest they be evaluated twice, once by the
* local plan and once by the scan.
*/
if (outer_plan) {
ListCell *lc = NULL;
/*
* Right now, we only consider grouping and aggregation beyond
* joins. Queries involving aggregates or grouping do not require
* EPQ mechanism, hence should not have an outer plan here.
*/
Assert(!IS_UPPER_REL(foreignrel));
/*
* First, update the plan's qual list if possible. In some cases
* the quals might be enforced below the topmost plan level, in
* which case we'll fail to remove them; it's not worth working
* harder than this.
*/
foreach (lc, local_exprs) {
Node *qual = (Node *)lfirst(lc);
outer_plan->qual = list_delete(outer_plan->qual, qual);
/*
* For an inner join the local conditions of foreign scan plan
* can be part of the joinquals as well. (They might also be
* in the mergequals or hashquals, but we can't touch those
* without breaking the plan.)
*/
if (IsA(outer_plan, NestLoop) || IsA(outer_plan, MergeJoin) || IsA(outer_plan, HashJoin)) {
Join *join_plan = (Join *)outer_plan;
if (join_plan->jointype == JOIN_INNER) {
join_plan->joinqual = list_delete(join_plan->joinqual, qual);
}
}
}
/*
* Now fix the subplan's tlist --- this might result in inserting
* a Result node atop the plan tree.
*/
outer_plan = change_plan_targetlist(root, outer_plan, fdw_scan_tlist);
}
}
/*
* Build the query string to be sent for execution, and identify
* expressions to be sent as parameters.
*/
initStringInfo(&sql);
deparseSelectStmtForRel(&sql, root, foreignrel, fdw_scan_tlist, remote_exprs, best_path->path.pathkeys,
has_final_sort, has_limit, false, &retrieved_attrs, &params_list);
/* Remember remote_exprs for possible use by postgresPlanDirectModify */
fpinfo->final_remote_exprs = remote_exprs;
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match order in enum FdwScanPrivateIndex.
*/
fdw_private = list_make3(makeString(sql.data), retrieved_attrs, makeInteger(fpinfo->fetch_size));
if (IS_JOIN_REL(foreignrel) || IS_UPPER_REL(foreignrel)) {
fdw_private = lappend(fdw_private, makeString(fpinfo->relation_name));
}
/*
* Create the ForeignScan node for the given relation.
*
* Note that the remote parameter expressions are stored in the fdw_exprs
* field of the finished plan node; we can't keep them in private state
* because then they wouldn't be subject to later planner processing.
*/
return make_foreignscan(tlist, local_exprs, scan_relid, params_list, fdw_private, fdw_scan_tlist, fdw_recheck_quals,
outer_plan);
}
/*
* Construct a tuple descriptor for the scan tuples handled by a foreign join.
*/
static TupleDesc get_tupdesc_for_join_scan_tuples(ForeignScanState *node)
{
ForeignScan *fsplan = (ForeignScan *)node->ss.ps.plan;
EState *estate = node->ss.ps.state;
TupleDesc tupdesc;
/*
* The core code has already set up a scan tuple slot based on
* fsplan->fdw_scan_tlist, and this slot's tupdesc is mostly good enough,
* but there's one case where it isn't. If we have any whole-row row
* identifier Vars, they may have vartype RECORD, and we need to replace
* that with the associated table's actual composite type. This ensures
* that when we read those ROW() expression values from the remote server,
* we can convert them to a composite type the local server knows.
*/
tupdesc = CreateTupleDescCopy(node->ss.ss_ScanTupleSlot->tts_tupleDescriptor);
for (int i = 0; i < tupdesc->natts; i++) {
Form_pg_attribute att = TupleDescAttr(tupdesc, i);
Var *var = NULL;
RangeTblEntry *rte = NULL;
Oid reltype;
/* Nothing to do if it's not a generic RECORD attribute */
if (att->atttypid != RECORDOID || att->atttypmod >= 0) {
continue;
}
/*
* If we can't identify the referenced table, do nothing. This'll
* likely lead to failure later, but perhaps we can muddle through.
*/
var = (Var *)list_nth_node(TargetEntry, fsplan->fdw_scan_tlist, i)->expr;
if (!IsA(var, Var) || var->varattno != 0) {
continue;
}
rte = (RangeTblEntry*)list_nth(estate->es_range_table, var->varno - 1);
if (rte->rtekind != RTE_RELATION) {
continue;
}
reltype = get_rel_type_id(rte->relid);
if (!OidIsValid(reltype)) {
continue;
}
att->atttypid = reltype;
/* shouldn't need to change anything else */
}
return tupdesc;
}
/*
* postgresBeginForeignScan
* Initiate an executor scan of a foreign PostgreSQL table.
*/
static void postgresBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *)node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwScanState *fsstate = NULL;
int numParams;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY) {
return;
}
/*
* We'll save private state in node->fdw_state.
*/
fsstate = (PgFdwScanState *)palloc0(sizeof(PgFdwScanState));
node->fdw_state = (void *)fsstate;
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
fsstate->conn = GetConnectionByFScanState(node, false);
/* Assign a unique ID for my cursor */
fsstate->cursor_number = GetCursorNumber(fsstate->conn);
fsstate->cursor_exists = false;
/* Get private info created by planner functions. */
fsstate->query = strVal(list_nth(fsplan->fdw_private, FdwScanPrivateSelectSql));
fsstate->retrieved_attrs = (List *)list_nth(fsplan->fdw_private, FdwScanPrivateRetrievedAttrs);
fsstate->fetch_size = intVal(list_nth(fsplan->fdw_private, FdwScanPrivateFetchSize));
/* Create contexts for batches of tuples and per-tuple temp workspace. */
fsstate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt, "postgres_fdw tuple data", ALLOCSET_DEFAULT_SIZES);
fsstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt, "postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MAXSIZE);
/*
* Get info we'll need for converting data fetched from the foreign server
* into local representation and error reporting during that process.
*/
if (fsplan->scan.scanrelid > 0) {
fsstate->rel = node->ss.ss_currentRelation;
fsstate->tupdesc = RelationGetDescr(fsstate->rel);
} else {
fsstate->rel = NULL;
fsstate->tupdesc = get_tupdesc_for_join_scan_tuples(node);
}
fsstate->attinmeta = TupleDescGetAttInMetadata(fsstate->tupdesc);
/*
* Prepare for processing of parameters used in remote query, if any.
*/
numParams = list_length(fsplan->fdw_exprs);
fsstate->numParams = numParams;
if (numParams > 0) {
prepare_query_params((PlanState *)node, fsplan->fdw_exprs, numParams, &fsstate->param_flinfo,
&fsstate->param_exprs, &fsstate->param_values);
}
}
/*
* postgresIterateForeignScan
* Retrieve next row from the result set, or clear tuple slot to indicate
* EOF.
*/
static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *)node->fdw_state;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
/*
* If this is the first call after Begin or ReScan, we need to create the
* cursor on the remote side.
*/
if (!fsstate->cursor_exists) {
create_cursor(node);
}
/*
* Get some more tuples, if we've run out.
*/
if (fsstate->next_tuple >= fsstate->num_tuples) {
/* No point in another fetch if we already detected EOF, though. */
if (!fsstate->eof_reached) {
fetch_more_data(node);
}
/* If we didn't get any tuples, must be end of data. */
if (fsstate->next_tuple >= fsstate->num_tuples) {
return ExecClearTuple(slot);
}
}
/*
* Return the next tuple.
*/
(void)ExecStoreTuple(fsstate->tuples[fsstate->next_tuple++], slot, InvalidBuffer, false);
return slot;
}
/*
* postgresReScanForeignScan
* Restart the scan.
*/
static void postgresReScanForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *)node->fdw_state;
char sql[64] = {'\0'};
int rc;
/* If we haven't created the cursor yet, nothing to do. */
if (!fsstate->cursor_exists) {
return;
}
/*
* If any internal parameters affecting this node have changed, we'd
* better destroy and recreate the cursor. Otherwise, rewinding it should
* be good enough. If we've only fetched zero or one batch, we needn't
* even rewind the cursor, just rescan what we have.
*/
if (node->ss.ps.chgParam != NULL) {
fsstate->cursor_exists = false;
rc = snprintf_s(sql, sizeof(sql), sizeof(sql) - 1, "CLOSE c%u", fsstate->cursor_number);
securec_check_ss(rc, "", "");
} else if (fsstate->fetch_ct_2 > 1) {
rc = snprintf_s(sql, sizeof(sql), sizeof(sql) - 1, "MOVE BACKWARD ALL IN c%u", fsstate->cursor_number);
securec_check_ss(rc, "", "");
} else {
/* Easy: just rescan what we already have in memory, if anything */
fsstate->next_tuple = 0;
return;
}
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult* res = pgfdw_exec_query(fsstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
pgfdw_report_error(ERROR, res, fsstate->conn, true, sql);
}
PQclear(res);
/* Now force a fresh FETCH. */
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
}
/*
* postgresEndForeignScan
* Finish scanning foreign table and dispose objects used for this scan
*/
static void postgresEndForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *)node->fdw_state;
/* if fsstate is NULL, we are in EXPLAIN; nothing to do */
if (fsstate == NULL) {
return;
}
/* Close the cursor if open, to prevent accumulation of cursors */
if (fsstate->cursor_exists) {
close_cursor(fsstate->conn, fsstate->cursor_number);
}
/* Release remote connection */
ReleaseConnection(fsstate->conn);
fsstate->conn = NULL;
/* MemoryContexts will be deleted automatically. */
}
/*
* postgresAddForeignUpdateTargets
* Add resjunk column(s) needed for update/delete on a foreign table
*/
static void postgresAddForeignUpdateTargets(Query *parsetree, RangeTblEntry *target_rte, Relation target_relation)
{
/*
* In postgres_fdw, what we need is the ctid, same as for a regular table.
* Make a Var representing the desired value
*/
Var* var = makeVar((Index)linitial_int(parsetree->resultRelations), SelfItemPointerAttributeNumber,
TIDOID, -1, InvalidOid, 0);
/* Wrap it in a resjunk TLE with the right name ... */
const char *attrname = "ctid";
TargetEntry* tle = makeTargetEntry((Expr *)var, list_length(parsetree->targetList) + 1, pstrdup(attrname), true);
/* ... and add it to the query's targetlist */
parsetree->targetList = lappend(parsetree->targetList, tle);
/*
* Because of partition table, ctid alone cannot determine a tuple, and tableoid is required.
* Otherwise, the tuples that should not be operated will be operated.
* Foreign table can not distinguish the type of remote table at this time, so we always add it.
*/
Var* var2 = makeVar((Index)linitial_int(parsetree->resultRelations), TableOidAttributeNumber,
OIDOID, -1, InvalidOid, 0);
const char *attrname2 = "tableoid";
TargetEntry* tle2 = makeTargetEntry((Expr *)var2, list_length(parsetree->targetList) + 1, pstrdup(attrname2), true);
parsetree->targetList = lappend(parsetree->targetList, tle2);
}
/*
* postgresPlanForeignModify
* Plan an insert/update/delete operation on a foreign table
*
* Note: currently, the plan tree generated for UPDATE/DELETE will always
* include a ForeignScan that retrieves ctids (using SELECT FOR UPDATE)
* and then the ModifyTable node will have to execute individual remote
* UPDATE/DELETE commands. If there are no local conditions or joins
* needed, it'd be better to let the scan node do UPDATE/DELETE RETURNING
* and then do nothing at ModifyTable. Room for future optimization ...
*/
static List *postgresPlanForeignModify(PlannerInfo *root, ModifyTable *plan, Index resultRelation, int subplan_index)
{
CmdType operation = plan->operation;
RangeTblEntry *rte = planner_rt_fetch(resultRelation, root);
StringInfoData sql;
List *targetAttrs = NIL;
List *withCheckOptionList = NIL;
List *returningList = NIL;
List *retrieved_attrs = NIL;
/*
* Core code already has some lock on each rel being planned, so we can
* use NoLock here.
*/
Relation rel = heap_open(rte->relid, NoLock);
initStringInfo(&sql);
/*
* In an INSERT, we transmit all columns that are defined in the foreign
* table. In an UPDATE, if there are BEFORE ROW UPDATE triggers on the
* foreign table, we transmit all columns like INSERT; else we transmit
* only columns that were explicitly targets of the UPDATE, so as to avoid
* unnecessary data transmission. (We can't do that for INSERT since we
* would miss sending default values for columns not listed in the source
* statement, and for UPDATE if there are BEFORE ROW UPDATE triggers since
* those triggers might change values for non-target columns, in which
* case we would miss sending changed values for those columns.)
*/
if (operation == CMD_INSERT ||
(operation == CMD_UPDATE && rel->trigdesc && rel->trigdesc->trig_update_before_row)) {
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
for (attnum = 1; attnum <= tupdesc->natts; attnum++) {
Form_pg_attribute attr = &tupdesc->attrs[attnum - 1];
if (!attr->attisdropped) {
targetAttrs = lappend_int(targetAttrs, attnum);
}
}
} else if (operation == CMD_UPDATE) {
Bitmapset *tmpset = bms_copy(rte->updatedCols);
Bitmapset *allUpdatedCols = bms_union(tmpset, rte->extraUpdatedCols);
AttrNumber col;
while ((col = bms_first_member(allUpdatedCols)) >= 0) {
col += FirstLowInvalidHeapAttributeNumber;
if (col <= InvalidAttrNumber) { /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
}
targetAttrs = lappend_int(targetAttrs, col);
}
}
/*
* Extract the relevant WITH CHECK OPTION list if any.
*/
if (plan->withCheckOptionLists) {
withCheckOptionList = (List*)list_nth(plan->withCheckOptionLists, subplan_index);
}
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists) {
returningList = (List *)list_nth(plan->returningLists, subplan_index);
}
/*
* Construct the SQL command string.
*/
switch (operation) {
case CMD_INSERT:
deparseInsertSql(&sql, rte, resultRelation, rel, targetAttrs, withCheckOptionList, returningList,
&retrieved_attrs);
break;
case CMD_UPDATE:
deparseUpdateSql(&sql, rte, resultRelation, rel, targetAttrs, withCheckOptionList, returningList,
&retrieved_attrs);
break;
case CMD_DELETE:
deparseDeleteSql(&sql, rte, resultRelation, rel, returningList, &retrieved_attrs);
break;
default:
elog(ERROR, "unexpected operation: %d", (int)operation);
break;
}
heap_close(rel, NoLock);
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwModifyPrivateIndex, above.
*/
return list_make4(makeString(sql.data), targetAttrs, makeInteger((retrieved_attrs != NIL)), retrieved_attrs);
}
/*
* postgresBeginForeignModify
* Begin an insert/update/delete operation on a foreign table
*/
static void postgresBeginForeignModify(ModifyTableState *mtstate, ResultRelInfo *resultRelInfo, List *fdw_private,
int subplan_index, int eflags)
{
/*
* Do nothing in EXPLAIN (no ANALYZE) case. resultRelInfo->ri_FdwState
* stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY) {
return;
}
/* Deconstruct fdw_private data. */
char *query = strVal(list_nth(fdw_private, FdwModifyPrivateUpdateSql));
List *target_attrs = (List *)list_nth(fdw_private, FdwModifyPrivateTargetAttnums);
bool has_returning = (bool)intVal(list_nth(fdw_private, FdwModifyPrivateHasReturning));
List *retrieved_attrs = (List *)list_nth(fdw_private, FdwModifyPrivateRetrievedAttrs);
/* Find RTE. */
RangeTblEntry *rte = rt_fetch(resultRelInfo->ri_RangeTableIndex, mtstate->ps.state->es_range_table);
/* Construct an execution state. */
PgFdwModifyState *fmstate = createForeignModify(mtstate->ps.state, rte, resultRelInfo, mtstate->operation,
mtstate->mt_plans[subplan_index]->plan, query, target_attrs, has_returning, retrieved_attrs);
resultRelInfo->ri_FdwState = fmstate;
}
/*
* Construct an execution state of a foreign insert/update/delete operation
*/
static PgFdwModifyState *createForeignModify(EState *estate, RangeTblEntry *rte, ResultRelInfo *resultRelInfo,
CmdType operation, Plan *subplan, char *query, List *target_attrs, bool has_returning, List *retrieved_attrs)
{
PgFdwModifyState *fmstate = NULL;
Relation rel = resultRelInfo->ri_RelationDesc;
TupleDesc tupdesc = RelationGetDescr(rel);
Oid userid;
AttrNumber n_params;
Oid typefnoid;
bool isvarlena = false;
ListCell *lc = NULL;
/* Begin constructing PgFdwModifyState. */
fmstate = (PgFdwModifyState *)palloc0(sizeof(PgFdwModifyState));
fmstate->rel = rel;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
ForeignTable* table = GetForeignTable(RelationGetRelid(rel));
UserMapping* user = GetUserMapping(userid, table->serverid);
ForeignServer *server = GetForeignServer(table->serverid);
/* Open connection; report that we'll create a prepared statement. */
fmstate->conn = GetConnection(server, user, true);
fmstate->p_name = NULL; /* prepared statement not made yet */
/* Set up remote query information. */
fmstate->query = query;
fmstate->target_attrs = target_attrs;
fmstate->has_returning = has_returning;
fmstate->retrieved_attrs = retrieved_attrs;
/* Create context for per-tuple temp workspace. */
fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt, "postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE, ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MAXSIZE);
/* Prepare for input conversion of RETURNING results. */
if (fmstate->has_returning) {
fmstate->attinmeta = TupleDescGetAttInMetadata(tupdesc);
}
/* Prepare for output conversion of parameters used in prepared stmt. */
n_params = list_length(fmstate->target_attrs) + 2; // + ctid and tableoid
fmstate->p_flinfo = (FmgrInfo *)palloc0(sizeof(FmgrInfo) * n_params);
fmstate->p_nums = 0;
if (operation == CMD_UPDATE || operation == CMD_DELETE) {
Assert(subplan != NULL);
/* Find the ctid and tableoid resjunk column in the subplan's result */
fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist, "ctid");
if (!AttributeNumberIsValid(fmstate->ctidAttno)) {
elog(ERROR, "could not find junk ctid column");
}
fmstate->tboidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist, "tableoid");
if (!AttributeNumberIsValid(fmstate->ctidAttno)) {
elog(ERROR, "could not find junk tableoid column");
}
/* First and second transmittable parameter will be ctid and tableoid */
getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
getTypeOutputInfo(OIDOID, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
if (operation == CMD_INSERT || operation == CMD_UPDATE) {
/* Set up for remaining transmittable parameters */
foreach (lc, fmstate->target_attrs) {
int attnum = lfirst_int(lc);
Form_pg_attribute attr = &tupdesc->attrs[attnum - 1];
Assert(!attr->attisdropped);
getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
}
Assert(fmstate->p_nums <= n_params);
return fmstate;
}
/*
* postgresExecForeignInsert
* Insert one row into a foreign table
*/
static TupleTableSlot *postgresExecForeignInsert(EState *estate, ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *)resultRelInfo->ri_FdwState;
int n_rows;
if (fmstate == NULL) {
StringInfoData sql;
Index resultRelation = resultRelInfo->ri_RangeTableIndex;
Relation rel = resultRelInfo->ri_RelationDesc;
TupleDesc tupdesc = RelationGetDescr(rel);
List *targetAttrs = NIL;
List *retrieved_attrs = NIL;
RangeTblEntry *rte = rt_fetch(resultRelation, estate->es_range_table);
initStringInfo(&sql);
/* We transmit all columns that are defined in the foreign table. */
for (int attnum = 1; attnum <= tupdesc->natts; attnum++) {
Form_pg_attribute attr = &tupdesc->attrs[attnum - 1];
if (!attr->attisdropped) {
targetAttrs = lappend_int(targetAttrs, attnum);
}
}
deparseInsertSql(&sql, rte, resultRelation, rel, targetAttrs, NULL, NULL, &retrieved_attrs);
fmstate = createForeignModify(estate, rte, resultRelInfo, CMD_INSERT, NULL, sql.data, targetAttrs,
retrieved_attrs != NIL, retrieved_attrs);
resultRelInfo->ri_FdwState = fmstate;
}
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name) {
prepare_foreign_modify(fmstate);
}
/* Convert parameters needed by prepared statement to text form */
const char **p_values = convert_prep_stmt_params(fmstate, NULL, NULL, slot);
/*
* Execute the prepared statement.
*/
if (!PQsendQueryPrepared(fmstate->conn, fmstate->p_name, fmstate->p_nums, p_values, NULL, NULL, 0)) {
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
}
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult* res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) != (fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK)) {
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
}
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning) {
n_rows = PQntuples(res);
if (n_rows > 0) {
store_returning_result(fmstate, slot, res);
}
} else {
n_rows = atoi(PQcmdTuples(res));
}
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was inserted on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresExecForeignUpdate
* Update one row in a foreign table
*/
static TupleTableSlot *postgresExecForeignUpdate(EState *estate, ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *)resultRelInfo->ri_FdwState;
Datum citd_datum, tboidd_atum;
bool isNull = false;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name) {
prepare_foreign_modify(fmstate);
}
/* Get the ctid and tableoid that was passed up as a resjunk column */
citd_datum = ExecGetJunkAttribute(planSlot, fmstate->ctidAttno, &isNull);
/* shouldn't ever get a null result... */
if (isNull) {
elog(ERROR, "ctid is NULL");
}
tboidd_atum = ExecGetJunkAttribute(planSlot, fmstate->tboidAttno, &isNull);
/* shouldn't ever get a null result... */
if (isNull) {
elog(ERROR, "tableoid is NULL");
}
/* Convert parameters needed by prepared statement to text form */
const char **p_values = convert_prep_stmt_params(fmstate, (ItemPointer)DatumGetPointer(citd_datum),
(ItemPointer)DatumGetPointer(tboidd_atum), slot);
/*
* Execute the prepared statement.
*/
if (!PQsendQueryPrepared(fmstate->conn, fmstate->p_name, fmstate->p_nums, p_values, NULL, NULL, 0)) {
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
}
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult* res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) != (fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK)) {
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
}
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning) {
n_rows = PQntuples(res);
if (n_rows > 0) {
store_returning_result(fmstate, slot, res);
}
} else {
n_rows = atoi(PQcmdTuples(res));
}
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was updated on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresExecForeignDelete
* Delete one row from a foreign table
*/
static TupleTableSlot *postgresExecForeignDelete(EState *estate, ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *)resultRelInfo->ri_FdwState;
Datum citd_datum, tboidd_atum;
bool isNull = false;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name) {
prepare_foreign_modify(fmstate);
}
/* Get the ctid that was passed up as a resjunk column */
citd_datum = ExecGetJunkAttribute(planSlot, fmstate->ctidAttno, &isNull);
/* shouldn't ever get a null result... */
if (isNull) {
elog(ERROR, "ctid is NULL");
}
tboidd_atum = ExecGetJunkAttribute(planSlot, fmstate->tboidAttno, &isNull);
/* shouldn't ever get a null result... */
if (isNull) {
elog(ERROR, "tableoid is NULL");
}
/* Convert parameters needed by prepared statement to text form */
const char **p_values = convert_prep_stmt_params(fmstate, (ItemPointer)DatumGetPointer(citd_datum),
(ItemPointer)DatumGetPointer(tboidd_atum), NULL);
/*
* Execute the prepared statement.
*/
if (!PQsendQueryPrepared(fmstate->conn, fmstate->p_name, fmstate->p_nums, p_values, NULL, NULL, 0)) {
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
}
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult *res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) != (fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK)) {
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
}
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning) {
n_rows = PQntuples(res);
if (n_rows > 0) {
store_returning_result(fmstate, slot, res);
}
} else {
n_rows = atoi(PQcmdTuples(res));
}
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was deleted on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresEndForeignModify
* Finish an insert/update/delete operation on a foreign table
*/
static void postgresEndForeignModify(EState *estate, ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *)resultRelInfo->ri_FdwState;
/* If fmstate is NULL, we are in EXPLAIN; nothing to do */
if (fmstate == NULL) {
return;
}
/* If we created a prepared statement, destroy it */
if (fmstate->p_name) {
char sql[64] = {'\0'};
int rc = snprintf_s(sql, sizeof(sql), sizeof(sql) - 1, "DEALLOCATE %s", fmstate->p_name);
securec_check_ss(rc, "", "");
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult* res = pgfdw_exec_query(fmstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
pgfdw_report_error(ERROR, res, fmstate->conn, true, sql);
}
PQclear(res);
fmstate->p_name = NULL;
}
/* Release remote connection */
ReleaseConnection(fmstate->conn);
fmstate->conn = NULL;
}
/*
* postgresIsForeignRelUpdatable
* Determine whether a foreign table supports INSERT, UPDATE and/or
* DELETE.
*/
static int postgresIsForeignRelUpdatable(Relation rel)
{
ListCell *lc = NULL;
/*
* By default, all postgres_fdw foreign tables are assumed updatable. This
* can be overridden by a per-server setting, which in turn can be
* overridden by a per-table setting.
*/
bool updatable = true;
ForeignTable* table = GetForeignTable(RelationGetRelid(rel));
ForeignServer* server = GetForeignServer(table->serverid);
foreach (lc, server->options) {
DefElem *def = (DefElem *)lfirst(lc);
if (strcmp(def->defname, "updatable") == 0) {
updatable = defGetBoolean(def);
}
}
foreach (lc, table->options) {
DefElem *def = (DefElem *)lfirst(lc);
if (strcmp(def->defname, "updatable") == 0) {
updatable = defGetBoolean(def);
}
}
/*
* Currently "updatable" means support for INSERT, UPDATE and DELETE.
*/
return updatable ? (1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE) : 0;
}
/*
* postgresExplainForeignScan
* Produce extra output for EXPLAIN of a ForeignScan on a foreign table
*/
static void postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
ForeignScan *plan = castNode(ForeignScan, node->ss.ps.plan);
List *fdw_private = plan->fdw_private;
/*
* Identify foreign scans that are really joins or upper relations. The
* input looks something like "(1) LEFT JOIN (2)", and we must replace the
* digit string(s), which are RT indexes, with the correct relation names.
* We do that here, not when the plan is created, because we can't know
* what aliases ruleutils.c will assign at plan creation time.
*/
if (list_length(fdw_private) > FdwScanPrivateRelations) {
StringInfo relations;
char *rawrelations = NULL;
char *ptr = NULL;
int minrti, rtoffset;
rawrelations = strVal(list_nth(fdw_private, FdwScanPrivateRelations));
/*
* A difficulty with using a string representation of RT indexes is
* that setrefs.c won't update the string when flattening the
* rangetable. To find out what rtoffset was applied, identify the
* minimum RT index appearing in the string and compare it to the
* minimum member of plan->fs_relids. (We expect all the relids in
* the join will have been offset by the same amount; the Asserts
* below should catch it if that ever changes.)
*/
minrti = INT_MAX;
ptr = rawrelations;
while (*ptr) {
if (isdigit((unsigned char)*ptr)) {
int rti = strtol(ptr, &ptr, 10);
if (rti < minrti) {
minrti = rti;
}
} else {
ptr++;
}
}
rtoffset = bms_next_member(plan->fs_relids, -1) - minrti;
/* Now we can translate the string */
relations = makeStringInfo();
ptr = rawrelations;
while (*ptr) {
if (isdigit((unsigned char)*ptr)) {
int rti = strtol(ptr, &ptr, 10);
RangeTblEntry *rte = NULL;
char *relname = NULL;
char *refname = NULL;
rti += rtoffset;
Assert(bms_is_member(rti, plan->fs_relids));
rte = rt_fetch(rti, es->rtable);
Assert(rte->rtekind == RTE_RELATION);
/* This logic should agree with explain.c's ExplainTargetRel */
relname = get_rel_name(rte->relid);
if (es->verbose) {
char *name_space = get_namespace_name_or_temp(get_rel_namespace(rte->relid));
appendStringInfo(relations, "%s.%s", quote_identifier(name_space), quote_identifier(relname));
} else {
appendStringInfoString(relations, quote_identifier(relname));
}
refname = rte->eref->aliasname;
if (strcmp(refname, relname) != 0) {
appendStringInfo(relations, " %s", quote_identifier(refname));
}
} else {
appendStringInfoChar(relations, *ptr++);
}
}
ExplainPropertyText("Relations", relations->data, es);
}
/*
* Add remote query, when VERBOSE option is specified.
*/
if (es->verbose) {
char *sql = NULL;
sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainForeignModify
* Produce extra output for EXPLAIN of a ModifyTable on a foreign table
*/
static void postgresExplainForeignModify(ModifyTableState *mtstate, ResultRelInfo *rinfo, List *fdw_private,
int subplan_index, ExplainState *es)
{
if (es->verbose) {
char *sql = strVal(list_nth(fdw_private, FdwModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
static void postgresExplainForeignScanRemote(ForeignScanState *node, ExplainState *es)
{
ForeignScan *plan = castNode(ForeignScan, node->ss.ps.plan);
List *fdw_private = plan->fdw_private;
char *sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
/* 1. prepare the explain sql, only support inherit 'verbose' and 'costs' currently. */
int len = strlen(sql) + 64; // length of explain (..) sql;
char *esql = (char*)palloc(len);
errno_t rc = sprintf_s(esql, len, "EXPLAIN (VERBOSE %s, COSTS %s) %s",
es->verbose ? "ON" : "OFF",
es->costs ? "ON" : "OFF",
sql);
securec_check_ss(rc, "\0", "\0");
/* 2. print the explain sql*/
appendStringInfo(es->es_frs.str, "%s \n", esql);
/* 3. get and print the plan */
PGconn *conn = GetConnectionByFScanState(node, false);
PGresult *volatile res = pgfdw_exec_query(conn, esql);
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
appendStringInfo(es->es_frs.str,
"failed to get remote plan, error massage is:\n%s\n",
PQresultErrorField(res, PG_DIAG_MESSAGE_PRIMARY));
} else {
int numrows = PQntuples(res);
for (int i = 0; i < numrows; i++) {
appendStringInfo(es->es_frs.str, " %s\n", PQgetvalue(res, i, 0));
}
}
pfree(esql);
PQclear(res);
ReleaseConnection(conn);
}
/*
* estimate_path_cost_size
* Get cost and size estimates for a foreign scan on given foreign relation
* either a base relation or a join between foreign relations or an upper
* relation containing foreign relations.
*
* param_join_conds are the parameterization clauses with outer relations.
* pathkeys specify the expected sort order if any for given path being costed.
* fpextra specifies additional post-scan/join-processing steps such as the
* final sort and the LIMIT restriction.
*
* The function returns the cost and size estimates in p_rows, p_width,
* p_startup_cost and p_total_cost variables.
*/
static void estimate_path_cost_size(PlannerInfo *root, RelOptInfo *foreignrel, List *param_join_conds, List *pathkeys,
PgFdwPathExtraData *fpextra, double *p_rows, int *p_width, Cost *p_startup_cost, Cost *p_total_cost)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)foreignrel->fdw_private;
double rows;
double retrieved_rows;
int width;
Cost startup_cost;
Cost total_cost;
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction+join clauses. Otherwise,
* estimate rows using whatever statistics we have locally, in a way
* similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate) {
List *remote_param_join_conds = NIL;
List *local_param_join_conds = NIL;
StringInfoData sql;
PGconn *conn = NULL;
Selectivity local_sel;
QualCost local_cost;
List *fdw_scan_tlist = NIL;
List *remote_conds = NIL;
/* Required only to be passed to deparseSelectStmtForRel */
List *retrieved_attrs = NIL;
/*
* param_join_conds might contain both clauses that are safe to send
* across, and clauses that aren't.
*/
classifyConditions(root, foreignrel, param_join_conds, &remote_param_join_conds, &local_param_join_conds);
/* Build the list of columns to be fetched from the foreign server. */
if (IS_JOIN_REL(foreignrel) || IS_UPPER_REL(foreignrel)) {
fdw_scan_tlist = build_tlist_to_deparse(foreignrel);
} else {
fdw_scan_tlist = NIL;
}
/*
* The complete list of remote conditions includes everything from
* baserestrictinfo plus any extra join_conds relevant to this
* particular path.
*/
remote_conds = list_concat(remote_param_join_conds, fpinfo->remote_conds);
/*
* Construct EXPLAIN query including the desired SELECT, FROM, and
* WHERE clauses. Params and other-relation Vars are replaced by dummy
* values, so don't request params_list.
*/
initStringInfo(&sql);
appendStringInfoString(&sql, "EXPLAIN ");
deparseSelectStmtForRel(&sql, root, foreignrel, fdw_scan_tlist, remote_conds, pathkeys,
fpextra ? fpextra->has_final_sort : false, fpextra ? fpextra->has_limit : false, false, &retrieved_attrs,
NULL);
/* Get the remote estimate */
conn = GetConnection(fpinfo->server, fpinfo->user, false);
get_remote_estimate(sql.data, conn, &rows, &width, &startup_cost, &total_cost);
ReleaseConnection(conn);
retrieved_rows = rows;
/* Factor in the selectivity of the locally-checked quals */
local_sel = clauselist_selectivity(root, local_param_join_conds, foreignrel->relid, JOIN_INNER, NULL);
local_sel *= fpinfo->local_conds_sel;
rows = clamp_row_est(rows * local_sel);
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
total_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
cost_qual_eval(&local_cost, local_param_join_conds, root);
startup_cost += local_cost.startup;
total_cost += local_cost.per_tuple * retrieved_rows;
/*
* Add in tlist eval cost for each output row. In case of an
* aggregate, some of the tlist expressions such as grouping
* expressions will be evaluated remotely, so adjust the costs.
*/
if (IS_UPPER_REL(foreignrel)) {
QualCost tlist_cost;
cost_qual_eval(&tlist_cost, fdw_scan_tlist, root);
startup_cost -= tlist_cost.startup;
total_cost -= tlist_cost.startup;
total_cost -= tlist_cost.per_tuple * rows;
}
} else {
Cost run_cost = 0;
/*
* We don't support join conditions in this mode (hence, no
* parameterized paths can be made).
*/
Assert(param_join_conds == NIL);
/*
* We will come here again and again with different set of pathkeys or
* additional post-scan/join-processing steps that caller wants to
* cost. We don't need to calculate the cost/size estimates for the
* underlying scan, join, or grouping each time. Instead, use those
* estimates if we have cached them already.
*/
if (fpinfo->rel_startup_cost >= 0 && fpinfo->rel_total_cost >= 0) {
Assert(fpinfo->retrieved_rows >= 0);
rows = fpinfo->rows;
retrieved_rows = fpinfo->retrieved_rows;
width = fpinfo->width;
startup_cost = fpinfo->rel_startup_cost;
run_cost = fpinfo->rel_total_cost - fpinfo->rel_startup_cost;
/*
* If we estimate the costs of a foreign scan or a foreign join
* with additional post-scan/join-processing steps, the scan or
* join costs obtained from the cache wouldn't yet contain the
* eval costs for the final scan/join target, which would've been
* updated by apply_scanjoin_target_to_paths(); add the eval costs
* now.
*/
} else if (IS_JOIN_REL(foreignrel)) {
PgFdwRelationInfo *fpinfo_i;
PgFdwRelationInfo *fpinfo_o;
QualCost join_cost;
QualCost remote_conds_cost;
double nrows;
/* Use rows/width estimates made by the core code. */
rows = foreignrel->rows;
width = foreignrel->reltarget->width;
/* For join we expect inner and outer relations set */
Assert(fpinfo->innerrel && fpinfo->outerrel);
fpinfo_i = (PgFdwRelationInfo *)fpinfo->innerrel->fdw_private;
fpinfo_o = (PgFdwRelationInfo *)fpinfo->outerrel->fdw_private;
/* Estimate of number of rows in cross product */
nrows = fpinfo_i->rows * fpinfo_o->rows;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most nrows.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, nrows);
/*
* The cost of foreign join is estimated as cost of generating
* rows for the joining relations + cost for applying quals on the
* rows.
*/
/*
* Calculate the cost of clauses pushed down to the foreign server
*/
cost_qual_eval(&remote_conds_cost, fpinfo->remote_conds, root);
/* Calculate the cost of applying join clauses */
cost_qual_eval(&join_cost, fpinfo->joinclauses, root);
/*
* Startup cost includes startup cost of joining relations and the
* startup cost for join and other clauses. We do not include the
* startup cost specific to join strategy (e.g. setting up hash
* tables) since we do not know what strategy the foreign server
* is going to use.
*/
startup_cost = fpinfo_i->rel_startup_cost + fpinfo_o->rel_startup_cost;
startup_cost += join_cost.startup;
startup_cost += remote_conds_cost.startup;
startup_cost += fpinfo->local_conds_cost.startup;
/*
* Run time cost includes:
*
* 1. Run time cost (total_cost - startup_cost) of relations being
* joined
*
* 2. Run time cost of applying join clauses on the cross product
* of the joining relations.
*
* 3. Run time cost of applying pushed down other clauses on the
* result of join
*
* 4. Run time cost of applying nonpushable other clauses locally
* on the result fetched from the foreign server.
*/
run_cost = fpinfo_i->rel_total_cost - fpinfo_i->rel_startup_cost;
run_cost += fpinfo_o->rel_total_cost - fpinfo_o->rel_startup_cost;
run_cost += nrows * join_cost.per_tuple;
nrows = clamp_row_est(nrows * fpinfo->joinclause_sel);
run_cost += nrows * remote_conds_cost.per_tuple;
run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
} else if (IS_UPPER_REL(foreignrel)) {
RelOptInfo *outerrel = fpinfo->outerrel;
PgFdwRelationInfo *ofpinfo;
AggClauseCosts aggcosts;
double input_rows;
int numGroupCols;
double numGroups = 1;
unsigned int numDatanodes;
/* The upper relation should have its outer relation set */
Assert(outerrel);
/*
* This cost model is mixture of costing done for sorted and
* hashed aggregates in cost_agg(). We are not sure which
* strategy will be considered at remote side, thus for
* simplicity, we put all startup related costs in startup_cost
* and all finalization and run cost are added in total_cost.
*/
ofpinfo = (PgFdwRelationInfo *)outerrel->fdw_private;
/* Get rows from input rel */
input_rows = ofpinfo->rows;
/* Collect statistics about aggregates for estimating costs. */
MemSet(&aggcosts, 0, sizeof(AggClauseCosts));
if (root->parse->hasAggs) {
count_agg_clauses(root, (Node*)foreignrel->reltarget->exprs, &aggcosts);
count_agg_clauses(root, root->parse->havingQual, &aggcosts);
}
/* Get number of grouping columns and possible number of groups */
numGroupCols = list_length(root->parse->groupClause);
numDatanodes = ng_get_dest_num_data_nodes(root, foreignrel);
numGroups = estimate_num_groups(root,
get_sortgrouplist_exprs(root->parse->groupClause, fpinfo->grouped_tlist), input_rows, numDatanodes);
/*
* Get the retrieved_rows and rows estimates. If there are HAVING
* quals, account for their selectivity.
*/
if (root->parse->havingQual) {
/*
* Factor in the selectivity of the remotely-checked quals,
* openGauss not support calc selectivity of agg in having, so just using numGroups
*/
retrieved_rows = numGroups;
/* Factor in the selectivity of the locally-checked quals */
rows = clamp_row_est(retrieved_rows * fpinfo->local_conds_sel);
} else {
rows = retrieved_rows = numGroups;
}
/* Use width estimate made by the core code. */
width = foreignrel->reltarget->width;
/* -----
* Startup cost includes:
* 1. Startup cost for underneath input relation, adjusted for
* tlist replacement by apply_scanjoin_target_to_paths()
* 2. Cost of performing aggregation, per cost_agg()
* -----
*/
startup_cost = ofpinfo->rel_startup_cost;
startup_cost += aggcosts.transCost.startup;
startup_cost += aggcosts.transCost.per_tuple * input_rows;
startup_cost += aggcosts.finalCost;
startup_cost += (u_sess->attr.attr_sql.cpu_operator_cost * numGroupCols) * input_rows;
/* -----
* Run time cost includes:
* 1. Run time cost of underneath input relation, adjusted for
* tlist replacement by apply_scanjoin_target_to_paths()
* 2. Run time cost of performing aggregation, per cost_agg()
* -----
*/
run_cost = ofpinfo->rel_total_cost - ofpinfo->rel_startup_cost;
run_cost += aggcosts.finalCost * numGroups;
run_cost += u_sess->attr.attr_sql.cpu_tuple_cost * numGroups;
/* Account for the eval cost of HAVING quals, if any */
if (root->parse->havingQual) {
QualCost remote_cost;
/* Add in the eval cost of the remotely-checked quals */
cost_qual_eval(&remote_cost, fpinfo->remote_conds, root);
startup_cost += remote_cost.startup;
run_cost += remote_cost.per_tuple * numGroups;
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
run_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
}
} else {
Cost cpu_per_tuple;
/* Use rows/width estimates made by set_baserel_size_estimates. */
rows = foreignrel->rows;
width = foreignrel->reltarget->width;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most foreignrel->tuples.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, foreignrel->tuples);
/*
* Cost as though this were a seqscan, which is pessimistic. We
* effectively imagine the local_conds are being evaluated
* remotely, too.
*/
startup_cost = 0;
run_cost = 0;
run_cost += u_sess->attr.attr_sql.seq_page_cost * foreignrel->pages;
startup_cost += foreignrel->baserestrictcost.startup;
cpu_per_tuple = u_sess->attr.attr_sql.cpu_tuple_cost + foreignrel->baserestrictcost.per_tuple;
run_cost += cpu_per_tuple * foreignrel->tuples;
}
/*
* Without remote estimates, we have no real way to estimate the cost
* of generating sorted output. It could be free if the query plan
* the remote side would have chosen generates properly-sorted output
* anyway, but in most cases it will cost something. Estimate a value
* high enough that we won't pick the sorted path when the ordering
* isn't locally useful, but low enough that we'll err on the side of
* pushing down the ORDER BY clause when it's useful to do so.
*/
if (pathkeys != NIL) {
if (IS_UPPER_REL(foreignrel)) {
Assert(foreignrel->reloptkind == RELOPT_UPPER_REL && fpinfo->stage == UPPERREL_GROUP_AGG);
adjust_foreign_grouping_path_cost(root, pathkeys, retrieved_rows, width, fpextra->limit_tuples,
&startup_cost, &run_cost);
} else {
startup_cost *= DEFAULT_FDW_SORT_MULTIPLIER;
run_cost *= DEFAULT_FDW_SORT_MULTIPLIER;
}
}
total_cost = startup_cost + run_cost;
/* Adjust the cost estimates if we have LIMIT */
if (fpextra && fpextra->has_limit) {
adjust_limit_rows_costs(&rows, &startup_cost, &total_cost, fpextra->offset_est, fpextra->count_est);
retrieved_rows = rows;
}
}
/*
* Cache the retrieved rows and cost estimates for scans, joins, or
* groupings without any parameterization, pathkeys, or additional
* post-scan/join-processing steps, before adding the costs for
* transferring data from the foreign server. These estimates are useful
* for costing remote joins involving this relation or costing other
* remote operations on this relation such as remote sorts and remote
* LIMIT restrictions, when the costs can not be obtained from the foreign
* server. This function will be called at least once for every foreign
* relation without any parameterization, pathkeys, or additional
* post-scan/join-processing steps.
*/
if (pathkeys == NIL && param_join_conds == NIL && fpextra == NULL) {
fpinfo->retrieved_rows = retrieved_rows;
fpinfo->rel_startup_cost = startup_cost;
fpinfo->rel_total_cost = total_cost;
}
/*
* Add some additional cost factors to account for connection overhead
* (fdw_startup_cost), transferring data across the network
* (fdw_tuple_cost per retrieved row), and local manipulation of the data
* (cpu_tuple_cost per retrieved row).
*/
startup_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_tuple_cost * retrieved_rows;
total_cost += u_sess->attr.attr_sql.cpu_tuple_cost * retrieved_rows;
/*
* If we have LIMIT, we should prefer performing the restriction remotely
* rather than locally, as the former avoids extra row fetches from the
* remote that the latter might cause. But since the core code doesn't
* account for such fetches when estimating the costs of the local
* restriction (see create_limit_path()), there would be no difference
* between the costs of the local restriction and the costs of the remote
* restriction estimated above if we don't use remote estimates (except
* for the case where the foreignrel is a grouping relation, the given
* pathkeys is not NIL, and the effects of a bounded sort for that rel is
* accounted for in costing the remote restriction). Tweak the costs of
* the remote restriction to ensure we'll prefer it if LIMIT is a useful
* one.
*/
if (!fpinfo->use_remote_estimate && fpextra && fpextra->has_limit && fpextra->limit_tuples > 0 &&
fpextra->limit_tuples < fpinfo->rows) {
Assert(fpinfo->rows > 0);
total_cost -= (total_cost - startup_cost) * 0.05 * (fpinfo->rows - fpextra->limit_tuples) / fpinfo->rows;
}
/* Return results. */
*p_rows = rows;
*p_width = width;
*p_startup_cost = startup_cost;
*p_total_cost = total_cost;
}
/*
* Estimate costs of executing a SQL statement remotely.
* The given "sql" must be an EXPLAIN command.
*/
static void get_remote_estimate(const char *sql, PGconn *conn, double *rows, int *width, Cost *startup_cost,
Cost *total_cost)
{
PGresult *volatile res = NULL;
/* PGresult must be released before leaving this function. */
PG_TRY();
{
int n;
/*
* Execute EXPLAIN remotely.
*/
res = pgfdw_exec_query(conn, sql);
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
pgfdw_report_error(ERROR, res, conn, false, sql);
}
/*
* Extract cost numbers for topmost plan node. Note we search for a
* left paren from the end of the line to avoid being confused by
* other uses of parentheses.
*/
char *line = PQgetvalue(res, 0, 0);
if (strstr(line, "Bypass") != NULL) {
line = PQgetvalue(res, 1, 0);
}
char *p = strrchr(line, '(');
if (p == NULL) {
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
}
n = sscanf_s(p, "(cost=%lf..%lf rows=%lf width=%d)", startup_cost, total_cost, rows, width);
if (n != 4) {
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
}
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res) {
PQclear(res);
}
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Adjust the cost estimates of a foreign grouping path to include the cost of
* generating properly-sorted output.
*/
static void adjust_foreign_grouping_path_cost(PlannerInfo *root, List *pathkeys, double retrieved_rows, double width,
double limit_tuples, Cost *p_startup_cost, Cost *p_run_cost)
{
/*
* If the GROUP BY clause isn't sort-able, the plan chosen by the remote
* side is unlikely to generate properly-sorted output, so it would need
* an explicit sort; adjust the given costs with cost_sort(). Likewise,
* if the GROUP BY clause is sort-able but isn't a superset of the given
* pathkeys, adjust the costs with that function. Otherwise, adjust the
* costs by applying the same heuristic as for the scan or join case.
*/
if (!grouping_is_sortable(root->parse->groupClause) || !pathkeys_contained_in(pathkeys, root->group_pathkeys)) {
Path sort_path; /* dummy for result of cost_sort */
cost_sort(&sort_path, pathkeys, *p_startup_cost + *p_run_cost, retrieved_rows, width, 0.0,
u_sess->attr.attr_memory.work_mem, limit_tuples, root->glob->vectorized);
*p_startup_cost = sort_path.startup_cost;
*p_run_cost = sort_path.total_cost - sort_path.startup_cost;
} else {
/*
* The default extra cost seems too large for foreign-grouping cases;
* add 1/4th of that default.
*/
double sort_multiplier = 1.0 + (DEFAULT_FDW_SORT_MULTIPLIER - 1.0) * 0.25;
*p_startup_cost *= sort_multiplier;
*p_run_cost *= sort_multiplier;
}
}
/*
* Create cursor for node's query with current parameter values.
*/
static void create_cursor(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *)node->fdw_state;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = fsstate->numParams;
const char **values = fsstate->param_values;
PGconn *conn = fsstate->conn;
StringInfoData buf;
PGresult *res = NULL;
/*
* Construct array of query parameter values in text format. We do the
* conversions in the short-lived per-tuple context, so as not to cause a
* memory leak over repeated scans.
*/
if (numParams > 0) {
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
process_query_params(econtext, fsstate->param_flinfo, fsstate->param_exprs, values);
MemoryContextSwitchTo(oldcontext);
}
/* Construct the DECLARE CURSOR command */
initStringInfo(&buf);
appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s", fsstate->cursor_number, fsstate->query);
/*
* Notice that we pass NULL for paramTypes, thus forcing the remote server
* to infer types for all parameters. Since we explicitly cast every
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
*/
if (!PQsendQueryParams(conn, buf.data, numParams, NULL, values, NULL, NULL, 0)) {
pgfdw_report_error(ERROR, NULL, conn, false, buf.data);
}
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = pgfdw_get_result(conn, buf.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
pgfdw_report_error(ERROR, res, conn, true, fsstate->query);
}
PQclear(res);
/* Mark the cursor as created, and show no tuples have been retrieved */
fsstate->cursor_exists = true;
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
/* Clean up */
pfree(buf.data);
}
/*
* Fetch some more rows from the node's cursor.
*/
static void fetch_more_data(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *)node->fdw_state;
PGresult *volatile res = NULL;
MemoryContext oldcontext;
/*
* We'll store the tuples in the batch_cxt. First, flush the previous
* batch.
*/
fsstate->tuples = NULL;
MemoryContextReset(fsstate->batch_cxt);
oldcontext = MemoryContextSwitchTo(fsstate->batch_cxt);
/* PGresult must be released before leaving this function. */
PG_TRY();
{
PGconn *conn = fsstate->conn;
int numrows;
int i;
char sql[64] = {'\0'};
/* This is a regular synchronous fetch. */
errno_t rc = snprintf_s(sql, sizeof(sql), sizeof(sql), "FETCH %d FROM c%u", fsstate->fetch_size, fsstate->cursor_number);
securec_check_ss(rc, "\0", "\0");
res = pgfdw_exec_query(conn, sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
pgfdw_report_error(ERROR, res, conn, false, fsstate->query);
}
/* Convert the data into HeapTuples */
numrows = PQntuples(res);
fsstate->tuples = (HeapTuple *)palloc0(numrows * sizeof(HeapTuple));
fsstate->num_tuples = numrows;
fsstate->next_tuple = 0;
for (i = 0; i < numrows; i++) {
Assert(IsA(node->ss.ps.plan, ForeignScan));
fsstate->tuples[i] = make_tuple_from_result_row(res, i, fsstate->rel, fsstate->attinmeta,
fsstate->retrieved_attrs, node, fsstate->temp_cxt);
}
/* Update fetch_ct_2 */
if (fsstate->fetch_ct_2 < 2) {
fsstate->fetch_ct_2++;
}
/* Must be EOF if we didn't get as many tuples as we asked for. */
fsstate->eof_reached = (numrows < fsstate->fetch_size);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res) {
PQclear(res);
}
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcontext);
}
/*
* Force assorted GUC parameters to settings that ensure that we'll output
* data values in a form that is unambiguous to the remote server.
*
* This is rather expensive and annoying to do once per row, but there's
* little choice if we want to be sure values are transmitted accurately;
* we can't leave the settings in place between rows for fear of affecting
* user-visible computations.
*
* We use the equivalent of a function SET option to allow the settings to
* persist only until the caller calls reset_transmission_modes(). If an
* error is thrown in between, guc.c will take care of undoing the settings.
*
* The return value is the nestlevel that must be passed to
* reset_transmission_modes() to undo things.
*/
int set_transmission_modes(void)
{
int nestlevel = NewGUCNestLevel();
/*
* The values set here should match what pg_dump does. See also
* configure_remote_session in connection.c.
*/
if (u_sess->time_cxt.DateStyle != USE_ISO_DATES) {
(void)set_config_option("datestyle", "ISO", PGC_USERSET, PGC_S_SESSION, GUC_ACTION_SAVE, true, 0);
}
if (u_sess->attr.attr_common.IntervalStyle != INTSTYLE_POSTGRES) {
(void)set_config_option("intervalstyle", "postgres", PGC_USERSET, PGC_S_SESSION, GUC_ACTION_SAVE, true, 0);
}
if (u_sess->attr.attr_common.extra_float_digits < 3) {
(void)set_config_option("extra_float_digits", "3", PGC_USERSET, PGC_S_SESSION, GUC_ACTION_SAVE, true, 0);
}
return nestlevel;
}
/*
* Undo the effects of set_transmission_modes().
*/
void reset_transmission_modes(int nestlevel)
{
AtEOXact_GUC(true, nestlevel);
}
/*
* Utility routine to close a cursor.
*/
static void close_cursor(PGconn *conn, unsigned int cursor_number)
{
char sql[64];
int rc = snprintf_s(sql, sizeof(sql), sizeof(sql) - 1, "CLOSE c%u", cursor_number);
securec_check_ss(rc, "", "");
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult* res = pgfdw_exec_query(conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
pgfdw_report_error(ERROR, res, conn, true, sql);
}
PQclear(res);
}
/*
* prepare_foreign_modify
* Establish a prepared statement for execution of INSERT/UPDATE/DELETE
*/
static void prepare_foreign_modify(PgFdwModifyState *fmstate)
{
char prep_name[NAMEDATALEN];
/* Construct name we'll use for the prepared statement. */
int rc = snprintf_s(prep_name, sizeof(prep_name), sizeof(prep_name) - 1,
"pgsql_fdw_prep_%u", GetPrepStmtNumber(fmstate->conn));
securec_check_ss(rc, "", "");
char* p_name = pstrdup(prep_name);
/*
* We intentionally do not specify parameter types here, but leave the
* remote server to derive them by default. This avoids possible problems
* with the remote server using different type OIDs than we do. All of
* the prepared statements we use in this module are simple enough that
* the remote server will make the right choices.
*/
if (!PQsendPrepare(fmstate->conn, p_name, fmstate->query, 0, NULL)) {
pgfdw_report_error(ERROR, NULL, fmstate->conn, false, fmstate->query);
}
/*
* Get the result, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
PGresult* res = pgfdw_get_result(fmstate->conn, fmstate->query);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
}
PQclear(res);
/* This action shows that the prepare has been done. */
fmstate->p_name = p_name;
}
/*
* convert_prep_stmt_params
* Create array of text strings representing parameter values
*
* tupleid is ctid to send, or NULL if none
* tableid is tableoid to send, or NULL if none
* slot is slot to get remaining parameters from, or NULL if none
*
* Data is constructed in temp_cxt; caller should reset that after use.
*/
static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate, ItemPointer tupleid, ItemPointer tableid,
TupleTableSlot *slot)
{
int pindex = 0;
MemoryContext oldcontext = MemoryContextSwitchTo(fmstate->temp_cxt);
const char **p_values = (const char **)palloc(sizeof(char *) * fmstate->p_nums);
/* 1st parameter should be ctid, if it's in use */
if (tupleid != NULL) {
/* don't need set_transmission_modes for TID output */
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex], PointerGetDatum(tupleid));
pindex++;
}
/* 2sd parameter should be tableoid, if it's in use */
if (tupleid != NULL) {
/* don't need set_transmission_modes for TABLEOID output */
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex], PointerGetDatum(tableid));
pindex++;
}
/* get following parameters from slot */
if (slot != NULL && fmstate->target_attrs != NIL) {
int nestlevel;
ListCell *lc = NULL;
nestlevel = set_transmission_modes();
foreach (lc, fmstate->target_attrs) {
int attnum = lfirst_int(lc);
Datum value;
bool isnull = false;
value = tableam_tslot_getattr(slot, attnum, &isnull);
if (isnull) {
p_values[pindex] = NULL;
} else {
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex], value);
}
pindex++;
}
reset_transmission_modes(nestlevel);
}
Assert(pindex == fmstate->p_nums);
(void)MemoryContextSwitchTo(oldcontext);
return p_values;
}
/*
* store_returning_result
* Store the result of a RETURNING clause
*
* On error, be sure to release the PGresult on the way out. Callers do not
* have PG_TRY blocks to ensure this happens.
*/
static void store_returning_result(PgFdwModifyState *fmstate, TupleTableSlot *slot, PGresult *res)
{
/* PGresult must be released before leaving this function. */
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(res, 0, fmstate->rel, fmstate->attinmeta, fmstate->retrieved_attrs, NULL,
fmstate->temp_cxt);
/* tuple will be deleted when it is cleared from the slot */
(void)ExecStoreTuple(newtup, slot, InvalidBuffer, true);
}
PG_CATCH();
{
if (res) {
PQclear(res);
}
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Prepare for processing of parameters used in remote query.
*/
static void prepare_query_params(PlanState *node, List *fdw_exprs, int numParams, FmgrInfo **param_flinfo,
List **param_exprs, const char ***param_values)
{
int i;
ListCell *lc = NULL;
Assert(numParams > 0);
/* Prepare for output conversion of parameters used in remote query. */
*param_flinfo = (FmgrInfo *)palloc0(sizeof(FmgrInfo) * numParams);
i = 0;
foreach (lc, fdw_exprs) {
Node *param_expr = (Node *)lfirst(lc);
Oid typefnoid;
bool isvarlena;
getTypeOutputInfo(exprType(param_expr), &typefnoid, &isvarlena);
fmgr_info(typefnoid, &(*param_flinfo)[i]);
i++;
}
/*
* Prepare remote-parameter expressions for evaluation. (Note: in
* practice, we expect that all these expressions will be just Params, so
* we could possibly do something more efficient than using the full
* expression-eval machinery for this. But probably there would be little
* benefit, and it'd require postgres_fdw to know more than is desirable
* about Param evaluation.)
*/
*param_exprs = ExecInitExprList(fdw_exprs, node);
/* Allocate buffer for text form of query parameters. */
*param_values = (const char **)palloc0(numParams * sizeof(char *));
}
/*
* Construct array of query parameter values in text format.
*/
static void process_query_params(ExprContext *econtext, FmgrInfo *param_flinfo, List *param_exprs,
const char **param_values)
{
int i;
ListCell *lc = NULL;
int nestlevel = set_transmission_modes();
i = 0;
foreach (lc, param_exprs) {
ExprState *expr_state = (ExprState *)lfirst(lc);
Datum expr_value;
bool isNull = false;
/* Evaluate the parameter expression */
expr_value = ExecEvalExpr(expr_state, econtext, &isNull, NULL);
/*
* Get string representation of each parameter value by invoking
* type-specific output function, unless the value is null.
*/
if (isNull) {
param_values[i] = NULL;
} else {
param_values[i] = OutputFunctionCall(&param_flinfo[i], expr_value);
}
i++;
}
reset_transmission_modes(nestlevel);
}
/*
* postgresAnalyzeForeignTable
* Test whether analyzing this foreign table is supported
*/
static bool postgresAnalyzeForeignTable(Relation relation, AcquireSampleRowsFunc *func, BlockNumber *totalpages,
void *additionalData, bool estimate_table_rownum)
{
StringInfoData sql;
PGresult *volatile res = NULL;
/* Return the row-analysis function pointer */
*func = postgresAcquireSampleRowsFunc;
/*
* Now we have to get the number of pages. It's annoying that the ANALYZE
* API requires us to return that now, because it forces some duplication
* of effort between this routine and postgresAcquireSampleRowsFunc. But
* it's probably not worth redefining that API at this point.
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
ForeignTable* table = GetForeignTable(RelationGetRelid(relation));
ForeignServer* server = GetForeignServer(table->serverid);
UserMapping* user = GetUserMapping(relation->rd_rel->relowner, server->serverid);
PGconn* conn = GetConnection(server, user, false);
/*
* Construct command to get page count for relation.
*/
initStringInfo(&sql);
deparseAnalyzeSizeSql(&sql, relation);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = pgfdw_exec_query(conn, sql.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
pgfdw_report_error(ERROR, res, conn, false, sql.data);
}
if (PQntuples(res) != 1 || PQnfields(res) != 1) {
elog(ERROR, "unexpected result from deparseAnalyzeSizeSql query");
}
*totalpages = strtoul(PQgetvalue(res, 0, 0), NULL, 10);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res) {
PQclear(res);
}
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return true;
}
/*
* Acquire a random sample of rows from foreign table managed by postgres_fdw.
*
* We fetch the whole table from the remote side and pick out some sample rows.
*
* Selected rows are returned in the caller-allocated array rows[],
* which must have at least targrows entries.
* The actual number of rows selected is returned as the function result.
* We also count the total number of rows in the table and return it into
* *totalrows. Note that *totaldeadrows is always set to 0.
*
* Note that the returned list of rows is not always in order by physical
* position in the table. Therefore, correlation estimates derived later
* may be meaningless, but it's OK because we don't use the estimates
* currently (the planner only pays attention to correlation for indexscans).
*/
static int postgresAcquireSampleRowsFunc(Relation relation, int elevel, HeapTuple *rows, int targrows,
double *totalrows, double *totaldeadrows, void *additionalData, bool estimate_table_rownum)
{
PgFdwAnalyzeState astate;
unsigned int cursor_number;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Initialize workspace state */
astate.rel = relation;
astate.attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(relation));
astate.rows = rows;
astate.targrows = targrows;
astate.numrows = 0;
astate.samplerows = 0;
astate.rowstoskip = -1; /* -1 means not set yet */
astate.rstate = anl_init_selection_state(targrows);
/* Remember ANALYZE context, and create a per-tuple temp context */
astate.anl_cxt = CurrentMemoryContext;
astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext, "postgres_fdw temporary data", ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE, ALLOCSET_SMALL_MAXSIZE);
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
ForeignTable* table = GetForeignTable(RelationGetRelid(relation));
ForeignServer* server = GetForeignServer(table->serverid);
UserMapping* user = GetUserMapping(relation->rd_rel->relowner, server->serverid);
PGconn* conn = GetConnection(server, user, false);
/*
* Construct cursor that retrieves whole rows from remote.
*/
cursor_number = GetCursorNumber(conn);
initStringInfo(&sql);
appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number);
deparseAnalyzeSql(&sql, relation, &astate.retrieved_attrs);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = pgfdw_exec_query(conn, sql.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK) {
pgfdw_report_error(ERROR, res, conn, false, sql.data);
}
PQclear(res);
res = NULL;
/* Retrieve and process rows a batch at a time. */
for (;;) {
char fetch_sql[64] = {'\0'};
int fetch_size;
int numrows;
int i;
/* Allow users to cancel long query */
CHECK_FOR_INTERRUPTS();
/*
* XXX possible future improvement: if rowstoskip is large, we
* could issue a MOVE rather than physically fetching the rows,
* then just adjust rowstoskip and samplerows appropriately.
* The fetch size is arbitrary, but shouldn't be enormous.
*/
fetch_size = 100;
/* Fetch some rows */
int rc = snprintf_s(fetch_sql, sizeof(fetch_sql), sizeof(fetch_sql) - 1,
"FETCH %d FROM c%u", fetch_size, cursor_number);
securec_check_ss(rc, "", "");
res = pgfdw_exec_query(conn, fetch_sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK) {
pgfdw_report_error(ERROR, res, conn, false, sql.data);
}
/* Process whatever we got. */
numrows = PQntuples(res);
for (i = 0; i < numrows; i++) {
analyze_row_processor(res, i, &astate);
}
PQclear(res);
res = NULL;
/* Must be EOF if we didn't get all the rows requested. */
if (numrows < fetch_size) {
break;
}
}
/* Close the cursor, just to be tidy. */
close_cursor(conn, cursor_number);
}
PG_CATCH();
{
if (res) {
PQclear(res);
}
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
/* We assume that we have no dead tuple. */
*totaldeadrows = 0.0;
/* We've retrieved all living tuples from foreign server. */
*totalrows = astate.samplerows;
/*
* Emit some interesting relation info
*/
ereport(elevel, (errmsg("\"%s\": table contains %.0f rows, %d rows in sample", RelationGetRelationName(relation),
astate.samplerows, astate.numrows)));
return astate.numrows;
}
/*
* Collect sample rows from the result of query.
* - Use all tuples in sample until target # of samples are collected.
* - Subsequently, replace already-sampled tuples randomly.
*/
static void analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
{
int targrows = astate->targrows;
int pos; /* array index to store tuple in */
/* Always increment sample row counter. */
astate->samplerows += 1;
/*
* Determine the slot where this sample row should be stored. Set pos to
* negative value to indicate the row should be skipped.
*/
if (astate->numrows < targrows) {
/* First targrows rows are always included into the sample */
pos = astate->numrows++;
} else {
/*
* Now we start replacing tuples in the sample until we reach the end
* of the relation. Same algorithm as in acquire_sample_rows in
* analyze.c; see Jeff Vitter's paper.
*/
if (astate->rowstoskip < 0) {
astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows, &astate->rstate);
}
if (astate->rowstoskip <= 0) {
/* Choose a random reservoir element to replace. */
pos = (int)(targrows * anl_random_fract());
Assert(pos >= 0 && pos < targrows);
heap_freetuple(astate->rows[pos]);
} else {
/* Skip this tuple. */
pos = -1;
}
astate->rowstoskip -= 1;
}
if (pos >= 0) {
/*
* Create sample tuple from current result row, and store it in the
* position determined above. The tuple has to be created in anl_cxt.
*/
MemoryContext oldcontext = MemoryContextSwitchTo(astate->anl_cxt);
astate->rows[pos] = make_tuple_from_result_row(res, row, astate->rel, astate->attinmeta,
astate->retrieved_attrs, NULL, astate->temp_cxt);
(void)MemoryContextSwitchTo(oldcontext);
}
}
/*
* Create a tuple from the specified row of the PGresult.
*
* rel is the local representation of the foreign table, attinmeta is
* conversion data for the rel's tupdesc, and retrieved_attrs is an
* integer list of the table column numbers present in the PGresult.
* fsstate is the ForeignScan plan node's execution state.
* temp_context is a working context that can be reset after each tuple.
*
* Note: either rel or fsstate, but not both, can be NULL. rel is NULL
* if we're processing a remote join, while fsstate is NULL in a non-query
* context such as ANALYZE, or if we're processing a non-scan query node.
*/
static HeapTuple make_tuple_from_result_row(PGresult *res, int row, Relation rel, AttInMetadata *attinmeta,
List *retrieved_attrs, ForeignScanState *fsstate, MemoryContext temp_context)
{
HeapTuple tuple;
TupleDesc tupdesc;
Datum *values = NULL;
bool *nulls = NULL;
ItemPointer ctid = NULL;
Oid oid = InvalidOid, tableoid = InvalidOid;
ConversionLocation errpos;
ErrorContextCallback errcallback;
MemoryContext oldcontext;
ListCell *lc = NULL;
int j;
Assert(row < PQntuples(res));
/*
* Do the following work in a temp context that we reset after each tuple.
* This cleans up not only the data we have direct access to, but any
* cruft the I/O functions might leak.
*/
oldcontext = MemoryContextSwitchTo(temp_context);
/*
* Get the tuple descriptor for the row. Use the rel's tupdesc if rel is
* provided, otherwise look to the scan node's ScanTupleSlot.
*/
if (rel) {
tupdesc = RelationGetDescr(rel);
} else {
Assert(fsstate);
tupdesc = fsstate->ss.ss_ScanTupleSlot->tts_tupleDescriptor;
}
values = (Datum *)palloc0(tupdesc->natts * sizeof(Datum));
nulls = (bool *)palloc(tupdesc->natts * sizeof(bool));
/* Initialize to nulls for any columns not present in result */
errno_t rc = memset_s(nulls, tupdesc->natts * sizeof(bool), true, tupdesc->natts * sizeof(bool));
securec_check(rc, "\0", "\0");
/*
* Set up and install callback to report where conversion error occurs.
*/
errpos.cur_attno = 0;
errpos.rel = rel;
errpos.fsstate = fsstate;
errcallback.callback = conversion_error_callback;
errcallback.arg = (void *)&errpos;
errcallback.previous = t_thrd.log_cxt.error_context_stack;
t_thrd.log_cxt.error_context_stack = &errcallback;
/*
* i indexes columns in the relation, j indexes columns in the PGresult.
*/
j = 0;
foreach (lc, retrieved_attrs) {
int i = lfirst_int(lc);
char *valstr = NULL;
/* fetch next column's textual value */
if (PQgetisnull(res, row, j)) {
valstr = NULL;
} else {
valstr = PQgetvalue(res, row, j);
}
/*
* convert value to internal representation
*
* Note: we ignore system columns other than ctid and oid in result
*/
errpos.cur_attno = i;
if (i > 0) {
/* ordinary column */
Assert(i <= tupdesc->natts);
nulls[i - 1] = (valstr == NULL);
/* Apply the input function even to nulls, to support domains */
values[i - 1] = InputFunctionCall(&attinmeta->attinfuncs[i - 1], valstr, attinmeta->attioparams[i - 1],
attinmeta->atttypmods[i - 1]);
} else if (i == SelfItemPointerAttributeNumber) {
/* ctid */
if (valstr != NULL) {
Datum datum;
datum = DirectFunctionCall1(tidin, CStringGetDatum(valstr));
ctid = (ItemPointer)DatumGetPointer(datum);
}
} else if (i == ObjectIdAttributeNumber) {
/* oid */
if (valstr != NULL) {
Datum datum = DirectFunctionCall1(oidin, CStringGetDatum(valstr));
oid = DatumGetObjectId(datum);
}
} else if (i == TableOidAttributeNumber) {
/* tableoid */
if (valstr != NULL) {
Datum datum = DirectFunctionCall1(oidin, CStringGetDatum(valstr));
tableoid = DatumGetObjectId(datum);
}
}
errpos.cur_attno = 0;
j++;
}
/* Uninstall error context callback. */
t_thrd.log_cxt.error_context_stack = errcallback.previous;
/*
* Check we got the expected number of columns. Note: j == 0 and
* PQnfields == 1 is expected, since deparse emits a NULL if no columns.
*/
if (j > 0 && j != PQnfields(res)) {
elog(ERROR, "remote query result does not match the foreign table");
}
/*
* Build the result tuple in caller's memory context.
*/
MemoryContextSwitchTo(oldcontext);
tuple = heap_form_tuple(tupdesc, values, nulls);
/*
* If we have a CTID to return, install it in both t_self and t_ctid.
* t_self is the normal place, but if the tuple is converted to a
* composite Datum, t_self will be lost; setting t_ctid allows CTID to be
* preserved during EvalPlanQual re-evaluations (see ROW_MARK_COPY code).
*/
if (ctid) {
tuple->t_self = tuple->t_data->t_ctid = *ctid;
}
/*
* If we have an OID to return, install it.
*/
if (OidIsValid(oid)) {
HeapTupleSetOid(tuple, oid);
}
/*
* If we have an TABLEOID to return, install it.
*/
if (OidIsValid(tableoid)) {
tuple->t_tableOid = tableoid;
}
/* Clean up */
MemoryContextReset(temp_context);
return tuple;
}
/*
* Callback function which is called when error occurs during column value
* conversion. Print names of column and relation.
*
* Note that this function mustn't do any catalog lookups, since we are in
* an already-failed transaction. Fortunately, we can get the needed info
* from the relation or the query's rangetable instead.
*/
static void conversion_error_callback(void *arg)
{
ConversionLocation *errpos = (ConversionLocation *)arg;
Relation rel = errpos->rel;
ForeignScanState *fsstate = errpos->fsstate;
const char *attname = NULL;
const char *relname = NULL;
bool is_wholerow = false;
/*
* If we're in a scan node, always use aliases from the rangetable, for
* consistency between the simple-relation and remote-join cases. Look at
* the relation's tupdesc only if we're not in a scan node.
*/
if (fsstate) {
/* ForeignScan case */
ForeignScan *fsplan = castNode(ForeignScan, fsstate->ss.ps.plan);
int varno = 0;
AttrNumber colno = 0;
if (fsplan->scan.scanrelid > 0) {
/* error occurred in a scan against a foreign table */
varno = fsplan->scan.scanrelid;
colno = errpos->cur_attno;
} else {
/* error occurred in a scan against a foreign join */
TargetEntry *tle = NULL;
tle = list_nth_node(TargetEntry, fsplan->fdw_scan_tlist, errpos->cur_attno - 1);
/*
* Target list can have Vars and expressions. For Vars, we can
* get some information, however for expressions we can't. Thus
* for expressions, just show generic context message.
*/
if (IsA(tle->expr, Var)) {
Var *var = (Var *)tle->expr;
varno = var->varno;
colno = var->varattno;
}
}
if (varno > 0) {
EState *estate = fsstate->ss.ps.state;
RangeTblEntry *rte = exec_rt_fetch(varno, estate);
relname = rte->eref->aliasname;
if (colno == 0) {
is_wholerow = true;
} else if (colno > 0 && colno <= list_length(rte->eref->colnames)) {
attname = strVal(list_nth(rte->eref->colnames, colno - 1));
} else if (colno == SelfItemPointerAttributeNumber) {
attname = "ctid";
}
}
} else if (rel) {
/* Non-ForeignScan case (we should always have a rel here) */
TupleDesc tupdesc = RelationGetDescr(rel);
relname = RelationGetRelationName(rel);
if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts) {
Form_pg_attribute attr = TupleDescAttr(tupdesc, errpos->cur_attno - 1);
attname = NameStr(attr->attname);
} else if (errpos->cur_attno == SelfItemPointerAttributeNumber) {
attname = "ctid";
}
}
if (relname && is_wholerow){
errcontext("whole-row reference to foreign table \"%s\"", relname);
} else if (relname && attname) {
errcontext("column \"%s\" of foreign table \"%s\"", attname, relname);
} else {
errcontext("processing expression at position %d in select list", errpos->cur_attno);
}
}
/*
* Given an EquivalenceClass and a foreign relation, find an EC member
* that can be used to sort the relation remotely according to a pathkey
* using this EC.
*
* If there is more than one suitable candidate, return an arbitrary
* one of them. If there is none, return NULL.
*
* This checks that the EC member expression uses only Vars from the given
* rel and is shippable. Caller must separately verify that the pathkey's
* ordering operator is shippable.
*/
EquivalenceMember *find_em_for_rel(PlannerInfo *root, EquivalenceClass *ec, RelOptInfo *rel)
{
ListCell *lc = NULL;
foreach (lc, ec->ec_members) {
EquivalenceMember *em = (EquivalenceMember *)lfirst(lc);
/*
* Note we require !bms_is_empty, else we'd accept constant
* expressions which are not suitable for the purpose.
*/
if (bms_is_subset(em->em_relids, rel->relids) &&
!bms_is_empty(em->em_relids) &&
is_foreign_expr(root, rel, em->em_expr)) {
return em;
}
}
return NULL;
}
/*
* Find an EquivalenceClass member that is to be computed as a sort column
* in the given rel's reltarget, and is shippable.
*
* If there is more than one suitable candidate, return an arbitrary
* one of them. If there is none, return NULL.
*
* This checks that the EC member expression uses only Vars from the given
* rel and is shippable. Caller must separately verify that the pathkey's
* ordering operator is shippable.
*/
EquivalenceMember *find_em_for_rel_target(PlannerInfo *root, EquivalenceClass *ec, RelOptInfo *rel)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)rel->fdw_private;
List* target = fpinfo->complete_tlist;
ListCell *lc1 = NULL;
int i;
i = 0;
foreach (lc1, target) {
TargetEntry* te = (TargetEntry*)lfirst(lc1);
Expr *expr = te->expr;
Index sgref = te->ressortgroupref;
ListCell *lc2;
/* Ignore non-sort expressions */
if (sgref == 0 || get_sortgroupref_clause_noerr(sgref, root->parse->sortClause) == NULL) {
i++;
continue;
}
/* We ignore binary-compatible relabeling on both ends */
while (expr && IsA(expr, RelabelType)) {
expr = ((RelabelType *)expr)->arg;
}
/* Locate an EquivalenceClass member matching this expr, if any */
foreach (lc2, ec->ec_members) {
EquivalenceMember *em = (EquivalenceMember *)lfirst(lc2);
Expr *em_expr = NULL;
/* Don't match constants */
if (em->em_is_const) {
continue;
}
/* Ignore child members */
if (em->em_is_child) {
continue;
}
/* Match if same expression (after stripping relabel) */
em_expr = em->em_expr;
while (em_expr && IsA(em_expr, RelabelType)) {
em_expr = ((RelabelType *)em_expr)->arg;
}
if (!equal(em_expr, expr)) {
continue;
}
/* Check that expression (including relabels!) is shippable */
if (is_foreign_expr(root, rel, em->em_expr)) {
return em;
}
}
i++;
}
return NULL;
}
/*
* Assess whether the join between inner and outer relations can be pushed down
* to the foreign server. As a side effect, save information we obtain in this
* function to PgFdwRelationInfo passed in.
*/
static bool foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype, RelOptInfo *outerrel,
RelOptInfo *innerrel, List* restrictlist)
{
PgFdwRelationInfo *fpinfo = NULL;
PgFdwRelationInfo *fpinfo_o = NULL;
PgFdwRelationInfo *fpinfo_i = NULL;
ListCell *lc = NULL;
List *joinclauses = NIL;
/*
* We support pushing down INNER, LEFT, RIGHT and FULL OUTER joins.
* Constructing queries representing SEMI and ANTI joins is hard, hence
* not considered right now.
*/
if (jointype != JOIN_INNER && jointype != JOIN_LEFT && jointype != JOIN_RIGHT && jointype != JOIN_FULL) {
return false;
}
/*
* If either of the joining relations is marked as unsafe to pushdown, the
* join can not be pushed down.
*/
fpinfo = (PgFdwRelationInfo *)joinrel->fdw_private;
fpinfo_o = (PgFdwRelationInfo *)outerrel->fdw_private;
fpinfo_i = (PgFdwRelationInfo *)innerrel->fdw_private;
if (!fpinfo_o || !fpinfo_o->pushdown_safe || !fpinfo_i || !fpinfo_i->pushdown_safe) {
return false;
}
/*
* If joining relations have local conditions, those conditions are
* required to be applied before joining the relations. Hence the join can
* not be pushed down.
*/
if (fpinfo_o->local_conds || fpinfo_i->local_conds) {
return false;
}
/*
* Merge FDW options. We might be tempted to do this after we have deemed
* the foreign join to be OK. But we must do this beforehand so that we
* know which quals can be evaluated on the foreign server, which might
* depend on shippable_extensions.
*/
fpinfo->server = fpinfo_o->server;
merge_fdw_options(fpinfo, fpinfo_o, fpinfo_i);
/*
* Separate restrict list into join quals and pushed-down (other) quals.
*
* Join quals belonging to an outer join must all be shippable, else we
* cannot execute the join remotely. Add such quals to 'joinclauses'.
*
* Add other quals to fpinfo->remote_conds if they are shippable, else to
* fpinfo->local_conds. In an inner join it's okay to execute conditions
* either locally or remotely; the same is true for pushed-down conditions
* at an outer join.
*
* Note we might return failure after having already scribbled on
* fpinfo->remote_conds and fpinfo->local_conds. That's okay because we
* won't consult those lists again if we deem the join unshippable.
*/
joinclauses = NIL;
foreach (lc, restrictlist) {
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
bool is_remote_clause = is_foreign_expr(root, joinrel, rinfo->clause);
if (IS_OUTER_JOIN(jointype) && !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids)) {
if (!is_remote_clause) {
return false;
}
joinclauses = lappend(joinclauses, rinfo);
} else {
if (is_remote_clause) {
fpinfo->remote_conds = lappend(fpinfo->remote_conds, rinfo);
} else {
fpinfo->local_conds = lappend(fpinfo->local_conds, rinfo);
}
}
}
/*
* deparseExplicitTargetList() isn't smart enough to handle anything other
* than a Var. In particular, if there's some PlaceHolderVar that would
* need to be evaluated within this join tree (because there's an upper
* reference to a quantity that may go to NULL as a result of an outer
* join), then we can't try to push the join down because we'll fail when
* we get to deparseExplicitTargetList(). However, a PlaceHolderVar that
* needs to be evaluated *at the top* of this join tree is OK, because we
* can do that locally after fetching the results from the remote side.
*/
foreach (lc, root->placeholder_list) {
PlaceHolderInfo *phinfo = (PlaceHolderInfo*)lfirst(lc);
Relids relids;
/* PlaceHolderInfo refers to parent relids, not child relids. */
relids = joinrel->relids;
if (bms_is_subset(phinfo->ph_eval_at, relids) && bms_nonempty_difference(relids, phinfo->ph_eval_at)) {
return false;
}
}
/* Save the join clauses, for later use. */
fpinfo->joinclauses = joinclauses;
fpinfo->outerrel = outerrel;
fpinfo->innerrel = innerrel;
fpinfo->jointype = jointype;
/*
* By default, both the input relations are not required to be deparsed as
* subqueries, but there might be some relations covered by the input
* relations that are required to be deparsed as subqueries, so save the
* relids of those relations for later use by the deparser.
*/
fpinfo->make_outerrel_subquery = false;
fpinfo->make_innerrel_subquery = false;
Assert(bms_is_subset(fpinfo_o->lower_subquery_rels, outerrel->relids));
Assert(bms_is_subset(fpinfo_i->lower_subquery_rels, innerrel->relids));
fpinfo->lower_subquery_rels = bms_union(fpinfo_o->lower_subquery_rels, fpinfo_i->lower_subquery_rels);
/*
* Pull the other remote conditions from the joining relations into join
* clauses or other remote clauses (remote_conds) of this relation
* wherever possible. This avoids building subqueries at every join step.
*
* For an inner join, clauses from both the relations are added to the
* other remote clauses. For LEFT and RIGHT OUTER join, the clauses from
* the outer side are added to remote_conds since those can be evaluated
* after the join is evaluated. The clauses from inner side are added to
* the joinclauses, since they need to be evaluated while constructing the
* join.
*
* For a FULL OUTER JOIN, the other clauses from either relation can not
* be added to the joinclauses or remote_conds, since each relation acts
* as an outer relation for the other.
*
* The joining sides can not have local conditions, thus no need to test
* shippability of the clauses being pulled up.
*
* The foreign join path is not necessarily better than join foreign scan
* path, so we should use list_concat2.
*/
switch (jointype) {
case JOIN_INNER:
fpinfo->remote_conds = list_concat2(fpinfo->remote_conds, fpinfo_i->remote_conds);
fpinfo->remote_conds = list_concat2(fpinfo->remote_conds, fpinfo_o->remote_conds);
break;
case JOIN_LEFT:
fpinfo->joinclauses = list_concat2(fpinfo->joinclauses, fpinfo_i->remote_conds);
fpinfo->remote_conds = list_concat2(fpinfo->remote_conds, fpinfo_o->remote_conds);
break;
case JOIN_RIGHT:
fpinfo->joinclauses = list_concat2(fpinfo->joinclauses, fpinfo_o->remote_conds);
fpinfo->remote_conds = list_concat2(fpinfo->remote_conds, fpinfo_i->remote_conds);
break;
case JOIN_FULL:
/*
* In this case, if any of the input relations has conditions, we
* need to deparse that relation as a subquery so that the
* conditions can be evaluated before the join. Remember it in
* the fpinfo of this relation so that the deparser can take
* appropriate action. Also, save the relids of base relations
* covered by that relation for later use by the deparser.
*/
if (fpinfo_o->remote_conds) {
fpinfo->make_outerrel_subquery = true;
fpinfo->lower_subquery_rels = bms_add_members(fpinfo->lower_subquery_rels, outerrel->relids);
}
if (fpinfo_i->remote_conds) {
fpinfo->make_innerrel_subquery = true;
fpinfo->lower_subquery_rels = bms_add_members(fpinfo->lower_subquery_rels, innerrel->relids);
}
break;
default:
/* Should not happen, we have just checked this above */
elog(ERROR, "unsupported join type %d", jointype);
}
/*
* For an inner join, all restrictions can be treated alike. Treating the
* pushed down conditions as join conditions allows a top level full outer
* join to be deparsed without requiring subqueries.
*/
if (jointype == JOIN_INNER) {
Assert(!fpinfo->joinclauses);
fpinfo->joinclauses = fpinfo->remote_conds;
fpinfo->remote_conds = NIL;
}
/* Mark that this join can be pushed down safely */
fpinfo->pushdown_safe = true;
/* Get user mapping */
if (fpinfo->use_remote_estimate) {
if (fpinfo_o->use_remote_estimate) {
fpinfo->user = fpinfo_o->user;
} else {
fpinfo->user = fpinfo_i->user;
}
} else {
fpinfo->user = NULL;
}
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* Set the string describing this join relation to be used in EXPLAIN
* output of corresponding ForeignScan. Note that the decoration we add
* to the base relation names mustn't include any digits, or it'll confuse
* postgresExplainForeignScan.
*/
fpinfo->relation_name = psprintf("(%s) %s JOIN (%s)", fpinfo_o->relation_name, get_jointype_name(fpinfo->jointype),
fpinfo_i->relation_name);
/*
* Set the relation index. This is defined as the position of this
* joinrel in the join_rel_list list plus the length of the rtable list.
* Note that since this joinrel is at the end of the join_rel_list list
* when we are called, we can get the position by list_length.
*/
Assert(fpinfo->relation_index == 0); /* shouldn't be set yet */
fpinfo->relation_index = list_length(root->parse->rtable) + list_length(root->join_rel_list);
return true;
}
static void add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel, Path *epq_path)
{
List *useful_pathkeys_list = NIL; /* List of all pathkeys */
ListCell *lc = NULL;
useful_pathkeys_list = get_useful_pathkeys_for_relation(root, rel);
/* Create one path for each set of pathkeys we found above. */
foreach (lc, useful_pathkeys_list) {
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *useful_pathkeys = (List *)lfirst(lc);
estimate_path_cost_size(root, rel, NIL, useful_pathkeys, NULL, &rows, &width, &startup_cost, &total_cost);
/*
* The EPQ path must be at least as well sorted as the path itself, in
* case it gets used as input to a mergejoin.
*/
/* but openGauss not support create_sort_path(). */
Assert(epq_path == NULL);
if (IS_SIMPLE_REL(rel)) {
add_path(NULL, rel, (Path *)create_foreignscan_path(root, rel, startup_cost, total_cost,
useful_pathkeys, rel->lateral_relids, epq_path, NIL));
} else {
add_path(NULL, rel, (Path *)create_foreign_join_path(root, rel, NULL, rows, startup_cost, total_cost,
useful_pathkeys, rel->lateral_relids, epq_path, NIL));
}
}
}
/*
* Parse options from foreign server and apply them to fpinfo.
*
* New options might also require tweaking merge_fdw_options().
*/
static void apply_server_options(PgFdwRelationInfo *fpinfo)
{
ListCell *lc = NULL;
foreach (lc, fpinfo->server->options) {
DefElem *def = (DefElem *)lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0) {
fpinfo->use_remote_estimate = defGetBoolean(def);
} else if (strcmp(def->defname, "fdw_startup_cost") == 0) {
(void)parse_real(defGetString(def), &fpinfo->fdw_startup_cost, 0, NULL);
} else if (strcmp(def->defname, "fdw_tuple_cost") == 0) {
(void)parse_real(defGetString(def), &fpinfo->fdw_tuple_cost, 0, NULL);
} else if (strcmp(def->defname, "fetch_size") == 0) {
(void)parse_int(defGetString(def), &fpinfo->fetch_size, 0, NULL);
}
}
}
/*
* Parse options from foreign table and apply them to fpinfo.
*
* New options might also require tweaking merge_fdw_options().
*/
static void apply_table_options(PgFdwRelationInfo *fpinfo)
{
ListCell *lc = NULL;
foreach (lc, fpinfo->table->options) {
DefElem *def = (DefElem *)lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0) {
fpinfo->use_remote_estimate = defGetBoolean(def);
} else if (strcmp(def->defname, "fetch_size") == 0) {
(void)parse_int(defGetString(def), &fpinfo->fetch_size, 0, NULL);
}
}
}
/*
* Merge FDW options from input relations into a new set of options for a join
* or an upper rel.
*
* For a join relation, FDW-specific information about the inner and outer
* relations is provided using fpinfo_i and fpinfo_o. For an upper relation,
* fpinfo_o provides the information for the input relation; fpinfo_i is
* expected to NULL.
*/
static void merge_fdw_options(PgFdwRelationInfo *fpinfo, const PgFdwRelationInfo *fpinfo_o,
const PgFdwRelationInfo *fpinfo_i)
{
/* We must always have fpinfo_o. */
Assert(fpinfo_o);
/* fpinfo_i may be NULL, but if present the servers must both match. */
Assert(!fpinfo_i || fpinfo_i->server->serverid == fpinfo_o->server->serverid);
/*
* Copy the server specific FDW options. (For a join, both relations come
* from the same server, so the server options should have the same value
* for both relations.)
*/
fpinfo->fdw_startup_cost = fpinfo_o->fdw_startup_cost;
fpinfo->fdw_tuple_cost = fpinfo_o->fdw_tuple_cost;
fpinfo->shippable_extensions = fpinfo_o->shippable_extensions;
fpinfo->use_remote_estimate = fpinfo_o->use_remote_estimate;
fpinfo->fetch_size = fpinfo_o->fetch_size;
fpinfo->async_capable = fpinfo_o->async_capable;
/* Merge the table level options from either side of the join. */
if (fpinfo_i) {
/*
* We'll prefer to use remote estimates for this join if any table
* from either side of the join is using remote estimates. This is
* most likely going to be preferred since they're already willing to
* pay the price of a round trip to get the remote EXPLAIN. In any
* case it's not entirely clear how we might otherwise handle this
* best.
*/
fpinfo->use_remote_estimate = fpinfo_o->use_remote_estimate || fpinfo_i->use_remote_estimate;
/*
* Set fetch size to maximum of the joining sides, since we are
* expecting the rows returned by the join to be proportional to the
* relation sizes.
*/
fpinfo->fetch_size = Max(fpinfo_o->fetch_size, fpinfo_i->fetch_size);
/*
* We'll prefer to consider this join async-capable if any table from
* either side of the join is considered async-capable. This would be
* reasonable because in that case the foreign server would have its
* own resources to scan that table asynchronously, and the join could
* also be computed asynchronously using the resources.
*/
fpinfo->async_capable = fpinfo_o->async_capable || fpinfo_i->async_capable;
}
}
/*
* postgresGetForeignJoinPaths
* Add possible ForeignPath to joinrel, if join is safe to push down.
*/
static void postgresGetForeignJoinPaths(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *outerrel,
RelOptInfo *innerrel, JoinType jointype, SpecialJoinInfo* sjinfo, List* restrictlist)
{
PgFdwRelationInfo *fpinfo = NULL;
ForeignPath *joinpath = NULL;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/*
* Skip if this join combination has been considered already.
*/
if (joinrel->fdw_private) {
return;
}
/*
* This code does not work for joins with lateral references, since those
* must have parameterized paths, which we don't generate yet.
*/
if (!bms_is_empty(joinrel->lateral_relids)) {
return;
}
/*
* Create unfinished PgFdwRelationInfo entry which is used to indicate
* that the join relation is already considered, so that we won't waste
* time in judging safety of join pushdown and adding the same paths again
* if found safe. Once we know that this join can be pushed down, we fill
* the entry.
*/
fpinfo = (PgFdwRelationInfo *)palloc0(sizeof(PgFdwRelationInfo));
fpinfo->pushdown_safe = false;
joinrel->fdw_private = fpinfo;
/* attrs_used is only for base relations. */
fpinfo->attrs_used = NULL;
/*
* If there is a possibility that EvalPlanQual will be executed, we need
* to be able to reconstruct the row using scans of the base relations.
* GetExistingLocalJoinPath will find a suitable path for this purpose in
* the path list of the joinrel, if one exists. We must be careful to
* call it before adding any ForeignPath, since the ForeignPath might
* dominate the only suitable local path available. We also do it before
* calling foreign_join_ok(), since that function updates fpinfo and marks
* it as pushable if the join is found to be pushable.
*
* currently not support.
*/
if (root->parse->commandType == CMD_DELETE || root->parse->commandType == CMD_UPDATE || root->rowMarks) {
ereport(DEBUG3, (errmsg("could not push down foreign join because the EPQ maybe executed.")));
return;
}
if (!foreign_join_ok(root, joinrel, jointype, outerrel, innerrel, restrictlist)) {
return;
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
* The local conditions are applied after the join has been computed on
* the remote side like quals in WHERE clause, so pass jointype as
* JOIN_INNER.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root, fpinfo->local_conds, 0, JOIN_INNER, NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* If we are going to estimate costs locally, estimate the join clause
* selectivity here while we have special join info.
*/
if (!fpinfo->use_remote_estimate) {
fpinfo->joinclause_sel = clauselist_selectivity(root, fpinfo->joinclauses, 0, fpinfo->jointype, sjinfo);
}
/* Estimate costs for bare join relation */
estimate_path_cost_size(root, joinrel, NIL, NIL, NULL, &rows, &width, &startup_cost, &total_cost);
/* Now update this information in the joinrel */
joinrel->rows = rows;
joinrel->reltarget->width = width;
fpinfo->rows = rows;
fpinfo->width = width;
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
/*
* Create a new join path and add it to the joinrel which represents a
* join between foreign tables.
*/
joinpath = create_foreign_join_path(root, joinrel, NULL, /* default pathtarget */
rows, startup_cost, total_cost, NIL, /* no pathkeys */
joinrel->lateral_relids, NULL, NIL); /* no fdw_private */
/* Add generated path into joinrel by add_path(). */
add_path(NULL, joinrel, (Path *)joinpath);
/*
* Consider pathkeys for the join relation.
*/
add_paths_with_pathkeys_for_rel(root, joinrel, NULL);
/* XXX Consider parameterized paths for the join relation */
}
/*
* Assess whether the aggregation, grouping and having operations can be pushed
* down to the foreign server. As a side effect, save information we obtain in
* this function to PgFdwRelationInfo of the input relation.
*/
static bool foreign_grouping_ok(PlannerInfo *root, RelOptInfo *grouped_rel, Node *havingQual,
GroupPathExtraData *extra)
{
Query *query = root->parse;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)grouped_rel->fdw_private;
List *grouping_target = extra->targetList;
PgFdwRelationInfo *ofpinfo = NULL;
ListCell *lc = NULL;
int i;
List *tlist = NIL;
/* We currently don't support pushing Grouping Sets. */
if (query->groupingSets) {
return false;
}
/* Get the fpinfo of the underlying scan relation. */
ofpinfo = (PgFdwRelationInfo *)fpinfo->outerrel->fdw_private;
/*
* If underlying scan relation has any local conditions, those conditions
* are required to be applied before performing aggregation. Hence the
* aggregate cannot be pushed down.
*/
if (ofpinfo->local_conds) {
return false;
}
/*
* Examine grouping expressions, as well as other expressions we'd need to
* compute, and check whether they are safe to push down to the foreign
* server. All GROUP BY expressions will be part of the grouping target
* and thus there is no need to search for them separately. Add grouping
* expressions into target list which will be passed to foreign server.
*
* A tricky fine point is that we must not put any expression into the
* target list that is just a foreign param (that is, something that
* deparse.c would conclude has to be sent to the foreign server). If we
* do, the expression will also appear in the fdw_exprs list of the plan
* node, and setrefs.c will get confused and decide that the fdw_exprs
* entry is actually a reference to the fdw_scan_tlist entry, resulting in
* a broken plan. Somewhat oddly, it's OK if the expression contains such
* a node, as long as it's not at top level; then no match is possible.
*/
i = 0;
foreach (lc, grouping_target) {
TargetEntry* tle = (TargetEntry*)lfirst(lc);
Expr *expr = tle->expr;
Index sgref = tle->ressortgroupref;
ListCell *l = NULL;
/* Check whether this expression is part of GROUP BY clause */
if (sgref && get_sortgroupref_clause_noerr(sgref, query->groupClause)) {
/*
* If any GROUP BY expression is not shippable, then we cannot
* push down aggregation to the foreign server.
*/
if (!is_foreign_expr(root, grouped_rel, expr)) {
return false;
}
/*
* If it would be a foreign param, we can't put it into the tlist,
* so we have to fail.
*/
if (is_foreign_param(root, grouped_rel, expr)) {
return false;
}
/*
* Pushable, so add to tlist. We need to create a TLE for this
* expression and apply the sortgroupref to it. We cannot use
* add_to_flat_tlist() here because that avoids making duplicate
* entries in the tlist. If there are duplicate entries with
* distinct sortgrouprefs, we have to duplicate that situation in
* the output tlist.
*/
TargetEntry* new_tle = makeTargetEntry(expr, list_length(tlist) + 1, NULL, false);
new_tle->ressortgroupref = sgref;
tlist = lappend(tlist, new_tle);
} else {
/*
* Non-grouping expression we need to compute. Can we ship it
* as-is to the foreign server?
*/
if (is_foreign_expr(root, grouped_rel, expr) && !is_foreign_param(root, grouped_rel, expr)) {
/* Yes, so add to tlist as-is; OK to suppress duplicates */
tlist = add_to_flat_tlist(tlist, list_make1(expr));
} else {
/* Not pushable as a whole; extract its Vars and aggregates */
List *aggvars = NIL;
aggvars = pull_var_clause((Node *)expr, PVC_INCLUDE_AGGREGATES, PVC_REJECT_PLACEHOLDERS);
/*
* If any aggregate expression is not shippable, then we
* cannot push down aggregation to the foreign server. (We
* don't have to check is_foreign_param, since that certainly
* won't return true for any such expression.)
*/
if (!is_foreign_expr(root, grouped_rel, (Expr *)aggvars)) {
return false;
}
/*
* Add aggregates, if any, into the targetlist. Plain Vars
* outside an aggregate can be ignored, because they should be
* either same as some GROUP BY column or part of some GROUP
* BY expression. In either case, they are already part of
* the targetlist and thus no need to add them again. In fact
* including plain Vars in the tlist when they do not match a
* GROUP BY column would cause the foreign server to complain
* that the shipped query is invalid.
*/
foreach (l, aggvars) {
Expr *expr = (Expr *)lfirst(l);
if (IsA(expr, Aggref)) {
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
}
}
}
i++;
}
/*
* Classify the pushable and non-pushable HAVING clauses and save them in
* remote_conds and local_conds of the grouped rel's fpinfo.
*/
if (havingQual) {
ListCell *lc = NULL;
foreach (lc, (List *)havingQual) {
Expr *expr = (Expr *)lfirst(lc);
RestrictInfo *rinfo = NULL;
/*
* Currently, the core code doesn't wrap havingQuals in
* RestrictInfos, so we must make our own.
*/
Assert(!IsA(expr, RestrictInfo));
rinfo = make_restrictinfo(expr, true, false, false, root->qualSecurityLevel, grouped_rel->relids,
NULL, NULL);
if (is_foreign_expr(root, grouped_rel, expr)) {
fpinfo->remote_conds = lappend(fpinfo->remote_conds, rinfo);
} else {
fpinfo->local_conds = lappend(fpinfo->local_conds, rinfo);
}
}
}
/*
* If there are any local conditions, pull Vars and aggregates from it and
* check whether they are safe to pushdown or not.
*/
if (fpinfo->local_conds) {
List *aggvars = NIL;
ListCell *lc = NULL;
foreach (lc, fpinfo->local_conds) {
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
aggvars = list_concat(aggvars, pull_var_clause((Node *)rinfo->clause, PVC_INCLUDE_AGGREGATES, PVC_REJECT_PLACEHOLDERS));
}
foreach (lc, aggvars) {
Expr *expr = (Expr *)lfirst(lc);
/*
* If aggregates within local conditions are not safe to push
* down, then we cannot push down the query. Vars are already
* part of GROUP BY clause which are checked above, so no need to
* access them again here. Again, we need not check
* is_foreign_param for a foreign aggregate.
*/
if (IsA(expr, Aggref)) {
if (!is_foreign_expr(root, grouped_rel, expr)) {
return false;
}
tlist = add_to_flat_tlist(tlist, list_make1(expr));
}
}
}
/* Store generated targetlist */
fpinfo->grouped_tlist = tlist;
/* Safe to pushdown */
fpinfo->pushdown_safe = true;
/*
* Set # of retrieved rows and cached relation costs to some negative
* value, so that we can detect when they are set to some sensible values,
* during one (usually the first) of the calls to estimate_path_cost_size.
*/
fpinfo->retrieved_rows = -1;
fpinfo->rel_startup_cost = -1;
fpinfo->rel_total_cost = -1;
/*
* Set the string describing this grouped relation to be used in EXPLAIN
* output of corresponding ForeignScan. Note that the decoration we add
* to the base relation name mustn't include any digits, or it'll confuse
* postgresExplainForeignScan.
*/
fpinfo->relation_name = psprintf("Aggregate on (%s)", ofpinfo->relation_name);
return true;
}
static void init_upperrel_paths_context(FDWUpperRelCxt* ufdwCxt, Plan* mainPlan)
{
Assert(ufdwCxt->root != NULL && ufdwCxt->currentRel != NULL && ufdwCxt->spjExtra != NULL);
PlannerInfo* root = ufdwCxt->root;
if (root->parse->groupingSets) {
ufdwCxt->state = FDW_UPPER_REL_END;
return;
}
/* if the spj rel is unsafe to push down, upper rel is unsafe alse. */
PgFdwRelationInfo* fpinfo = (PgFdwRelationInfo *)ufdwCxt->currentRel->fdw_private;
if (!fpinfo->pushdown_safe) {
ufdwCxt->state = FDW_UPPER_REL_END;
return;
}
fpinfo->stage = UPPERREL_INIT;
/* the reltargetlist may bave been evaluted, we shoule adept it. */
ufdwCxt->currentRel->reltarget->exprs = extract_target_from_tel(ufdwCxt, fpinfo);
ufdwCxt->state = FDW_UPPER_REL_INIT;
}
static void create_upperrel_plan_if_needed(FDWUpperRelCxt* ufdwCxt, Plan* mainPlan)
{
ListCell* lc = NULL;
Path* bestPath = NULL;
set_cheapest(ufdwCxt->currentRel, ufdwCxt->root);
foreach(lc, ufdwCxt->currentRel->cheapest_total_path) {
Path* p = (Path*)lfirst(lc);
if (bestPath == NULL || bestPath->total_cost > p->total_cost) {
bestPath = p;
}
}
if (bestPath->total_cost < mainPlan->total_cost) {
ufdwCxt->resultPlan = create_plan(ufdwCxt->root, bestPath);
ufdwCxt->resultPathKeys = bestPath->pathkeys;
apply_tlist_labeling(ufdwCxt->resultPlan->targetlist, mainPlan->targetlist);
}
}
/*
* postgresGetForeignUpperPaths
* Add paths for post-join operations like aggregation, grouping etc. if
* corresponding operations are safe to push down.
*/
static void postgresGetForeignUpperPaths(FDWUpperRelCxt* ufdwCxt, UpperRelationKind stage, Plan* mainPlan)
{
Assert(ufdwCxt != NULL && ufdwCxt->state != FDW_UPPER_REL_END);
Assert(ufdwCxt->currentRel && ufdwCxt->currentRel->fdwroutine && ufdwCxt->currentRel->fdwroutine->GetForeignUpperPaths);
switch (stage) {
case UPPERREL_INIT:
init_upperrel_paths_context(ufdwCxt, mainPlan);
break;
case UPPERREL_GROUP_AGG:
case UPPERREL_ORDERED:
ufdwCxt->state = FDW_UPPER_REL_TRY;
_postgresGetForeignUpperPaths(ufdwCxt, stage);
break;
case UPPERREL_ROWMARKS:
case UPPERREL_LIMIT:
ufdwCxt->state = FDW_UPPER_REL_TRY;
break;
case UPPERREL_FINAL:
if (ufdwCxt->state == FDW_UPPER_REL_TRY) {
_postgresGetForeignUpperPaths(ufdwCxt, stage);
if (ufdwCxt->currentRel->pathlist != NIL) {
create_upperrel_plan_if_needed(ufdwCxt, mainPlan);
}
}
ufdwCxt->state = FDW_UPPER_REL_END;
break;
default:
ufdwCxt->state = FDW_UPPER_REL_END;
break;
}
}
static void _postgresGetForeignUpperPaths(FDWUpperRelCxt *ufdw_cxt, UpperRelationKind stage)
{
PgFdwRelationInfo *fpinfo = NULL;
RelOptInfo *input_rel = ufdw_cxt->currentRel;
RelOptInfo* output_rel = NULL;
/*
* If input rel is not safe to pushdown, then simply return as we cannot
* perform any post-join operations on the foreign server.
*/
if (!input_rel->fdw_private || !((PgFdwRelationInfo *)input_rel->fdw_private)->pushdown_safe) {
return;
}
fpinfo = (PgFdwRelationInfo *)palloc0(sizeof(PgFdwRelationInfo));
fpinfo->pushdown_safe = false;
fpinfo->stage = stage;
output_rel = make_upper_rel(ufdw_cxt, fpinfo);
switch (stage) {
case UPPERREL_GROUP_AGG:
add_foreign_grouping_paths(ufdw_cxt->root, input_rel, output_rel, ufdw_cxt->groupExtra);
break;
case UPPERREL_ORDERED:
add_foreign_ordered_paths(ufdw_cxt->root, input_rel, output_rel, ufdw_cxt->orderExtra);
break;
case UPPERREL_FINAL:
add_foreign_final_paths(ufdw_cxt->root, input_rel, output_rel, ufdw_cxt->finalExtra);
break;
default:
elog(ERROR, "unexpected upper relation: %d", (int)stage);
break;
}
ufdw_cxt->currentRel = output_rel;
}
/*
* add_foreign_grouping_paths
* Add foreign path for grouping and/or aggregation.
*
* Given input_rel represents the underlying scan. The paths are added to the
* given grouped_rel.
*/
static void add_foreign_grouping_paths(PlannerInfo *root, RelOptInfo *input_rel, RelOptInfo *grouped_rel,
GroupPathExtraData *extra)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = (PgFdwRelationInfo *)input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)grouped_rel->fdw_private;
ForeignPath *grouppath = NULL;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Nothing to be done, if there is no grouping or aggregation required. */
if (!parse->groupClause && !parse->groupingSets && !parse->hasAggs && !root->hasHavingQual) {
return;
}
/* save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* Assess if it is safe to push down aggregation and grouping.
*
* Use HAVING qual from extra. In case of child partition, it will have
* translated Vars.
*/
if (!foreign_grouping_ok(root, grouped_rel, extra->havingQual, extra)) {
return;
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. (Currently we create just a single
* path here, but in future it would be possible that we build more paths
* such as pre-sorted paths as in postgresGetForeignPaths and
* postgresGetForeignJoinPaths.) The best we can do for these conditions
* is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root, fpinfo->local_conds, 0, JOIN_INNER, NULL, false);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/* Estimate the cost of push down */
estimate_path_cost_size(root, grouped_rel, NIL, NIL, NULL, &rows, &width, &startup_cost, &total_cost);
/* Now update this information in the fpinfo */
fpinfo->rows = rows;
fpinfo->width = width;
fpinfo->startup_cost = startup_cost;
fpinfo->total_cost = total_cost;
/* Create and add foreign path to the grouping relation. */
grouppath = create_foreign_upper_path(root, grouped_rel, grouped_rel->reltarget->exprs, rows, startup_cost, total_cost,
NIL, /* no pathkeys */
NULL, NIL); /* no fdw_private */
/* Add generated path into grouped_rel by add_path(). */
add_path(root, grouped_rel, (Path *)grouppath);
}
/*
* add_foreign_ordered_paths
* Add foreign paths for performing the final sort remotely.
*
* Given input_rel contains the source-data Paths. The paths are added to the
* given ordered_rel.
*/
static void add_foreign_ordered_paths(PlannerInfo *root, RelOptInfo *input_rel, RelOptInfo *ordered_rel,
OrderPathExtraData *extra)
{
PgFdwRelationInfo *ifpinfo = (PgFdwRelationInfo *)input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)ordered_rel->fdw_private;
PgFdwPathExtraData *fpextra = NULL;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *fdw_private;
ForeignPath *ordered_path = NULL;
ListCell *lc = NULL;
/* Shouldn't get here unless the query has ORDER BY */
Assert(root->parse->sortClause);
/* Save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* If the input_rel is a base or join relation, we would already have
* considered pushing down the final sort to the remote server when
* creating pre-sorted foreign paths for that relation, because the
* query_pathkeys is set to the root->sort_pathkeys in that case (see
* standard_qp_callback()).
*/
if (input_rel->reloptkind == RELOPT_BASEREL || input_rel->reloptkind == RELOPT_JOINREL) {
Assert(equal(root->query_pathkeys, root->sort_pathkeys));
/* Safe to push down if the query_pathkeys is safe to push down */
fpinfo->pushdown_safe = ifpinfo->qp_is_pushdown_safe;
return;
}
/* The input_rel should be a grouping relation */
Assert(input_rel->reloptkind == RELOPT_UPPER_REL && ifpinfo->stage == UPPERREL_GROUP_AGG);
/*
* We try to create a path below by extending a simple foreign path for
* the underlying grouping relation to perform the final sort remotely,
* which is stored into the fdw_private list of the resulting path.
*/
/* Assess if it is safe to push down the final sort */
foreach (lc, root->sort_pathkeys) {
PathKey *pathkey = (PathKey *)lfirst(lc);
EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
/*
* is_foreign_expr would detect volatile expressions as well, but
* checking ec_has_volatile here saves some cycles.
*/
if (pathkey_ec->ec_has_volatile) {
return;
}
/*
* Can't push down the sort if pathkey's opfamily is not shippable.
*/
if (!is_builtin(pathkey->pk_opfamily)) {
return;
}
/*
* The EC must contain a shippable EM that is computed in input_rel's
* reltarget, else we can't push down the sort.
*/
if (find_em_for_rel_target(root, pathkey_ec, input_rel) == NULL) {
return;
}
}
/* Safe to push down */
fpinfo->pushdown_safe = true;
/* Construct PgFdwPathExtraData */
fpextra = (PgFdwPathExtraData *)palloc0(sizeof(PgFdwPathExtraData));
fpextra->target = ordered_rel->reltarget->exprs;
fpextra->has_final_sort = true;
/* Estimate the costs of performing the final sort remotely */
estimate_path_cost_size(root, input_rel, NIL, root->sort_pathkeys, fpextra, &rows, &width, &startup_cost,
&total_cost);
/*
* Build the fdw_private list that will be used by postgresGetForeignPlan.
* Items in the list must match order in enum FdwPathPrivateIndex.
*/
fdw_private = list_make2(makeInteger(1), makeInteger(0));
/* Create foreign ordering path */
ordered_path = create_foreign_upper_path(root, input_rel, ordered_rel->reltarget->exprs, rows, startup_cost,
total_cost, root->sort_pathkeys, NULL, /* no extra plan */
fdw_private);
/* and add it to the ordered_rel */
add_path(root, ordered_rel, (Path *)ordered_path);
}
/*
* add_foreign_final_paths
* Add foreign paths for performing the final processing remotely.
*
* Given input_rel contains the source-data Paths. The paths are added to the
* given final_rel.
*/
static void add_foreign_final_paths(PlannerInfo *root, RelOptInfo *input_rel, RelOptInfo *final_rel,
FinalPathExtraData *extra)
{
Query *parse = root->parse;
PgFdwRelationInfo *ifpinfo = (PgFdwRelationInfo *)input_rel->fdw_private;
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *)final_rel->fdw_private;
bool has_final_sort = false;
List *pathkeys = NIL;
PgFdwPathExtraData *fpextra = NULL;
bool save_use_remote_estimate = false;
double rows;
int width;
Cost startup_cost;
Cost total_cost;
List *fdw_private = NIL;
ForeignPath *final_path = NULL;
/*
* Currently, we only support this for SELECT commands
*/
if (parse->commandType != CMD_SELECT) {
return;
}
/*
* No work if there is no FOR UPDATE/SHARE clause and if there is no need
* to add a LIMIT node, input rel pathlist is the result, just copy it
*/
if (!parse->rowMarks && !extra->limit_needed) {
ListCell* lc = NULL;
Path* path = NULL;
ForeignPath *final_path = NULL;
foreach(lc, input_rel->pathlist) {
path = (Path*)lfirst(lc);
if (IsA(path, ForeignPath)) {
final_path = create_foreign_upper_path(root, path->parent, extra->targetList, path->rows,
path->startup_cost, path->total_cost, path->pathkeys, NULL, /* no extra plan */
((ForeignPath *)path)->fdw_private);
/* and add it to the final_rel */
add_path(root, final_rel, (Path *)final_path);
/* Safe to push down */
fpinfo->pushdown_safe = true;
}
}
return;
}
/* Save the input_rel as outerrel in fpinfo */
fpinfo->outerrel = input_rel;
/*
* Copy foreign table, foreign server, user mapping, FDW options etc.
* details from the input relation's fpinfo.
*/
fpinfo->table = ifpinfo->table;
fpinfo->server = ifpinfo->server;
fpinfo->user = ifpinfo->user;
merge_fdw_options(fpinfo, ifpinfo, NULL);
/*
* If there is no need to add a LIMIT node, there might be a ForeignPath
* in the input_rel's pathlist that implements all behavior of the query.
* Note: we would already have accounted for the query's FOR UPDATE/SHARE
* (if any) before we get here.
*/
if (!extra->limit_needed) {
ListCell *lc = NULL;
Assert(parse->rowMarks);
/*
* Grouping and aggregation are not supported with FOR UPDATE/SHARE,
* so the input_rel should be a base, join, or ordered relation; and
* if it's an ordered relation, its input relation should be a base or
* join relation.
*/
Assert(input_rel->reloptkind == RELOPT_BASEREL || input_rel->reloptkind == RELOPT_JOINREL ||
(input_rel->reloptkind == RELOPT_UPPER_REL && ifpinfo->stage == UPPERREL_ORDERED &&
(ifpinfo->outerrel->reloptkind == RELOPT_BASEREL || ifpinfo->outerrel->reloptkind == RELOPT_JOINREL)));
foreach (lc, input_rel->pathlist) {
Path *path = (Path *)lfirst(lc);
/*
* apply_scanjoin_target_to_paths() uses create_projection_path()
* to adjust each of its input paths if needed, whereas
* create_ordered_paths() uses apply_projection_to_path() to do
* that. So the former might have put a ProjectionPath on top of
* the ForeignPath; look through ProjectionPath and see if the
* path underneath it is ForeignPath.
*/
if (IsA(path, ForeignPath)) {
/*
* Create foreign final path; this gets rid of a
* no-longer-needed outer plan (if any), which makes the
* EXPLAIN output look cleaner
*/
final_path = create_foreign_upper_path(root, path->parent, extra->targetList, path->rows,
path->startup_cost, path->total_cost, path->pathkeys, NULL, /* no extra plan */
NULL); /* no fdw_private */
/* and add it to the final_rel */
add_path(root, final_rel, (Path *)final_path);
/* Safe to push down */
fpinfo->pushdown_safe = true;
return;
}
}
/*
* If we get here it means no ForeignPaths; since we would already
* have considered pushing down all operations for the query to the
* remote server, give up on it.
*/
return;
}
Assert(extra->limit_needed);
/*
* If the input_rel is an ordered relation, replace the input_rel with its
* input relation
*/
if (input_rel->reloptkind == RELOPT_UPPER_REL && ifpinfo->stage == UPPERREL_ORDERED) {
input_rel = ifpinfo->outerrel;
ifpinfo = (PgFdwRelationInfo *)input_rel->fdw_private;
has_final_sort = true;
pathkeys = root->sort_pathkeys;
}
/* The input_rel should be a base, join, or grouping relation */
Assert(input_rel->reloptkind == RELOPT_BASEREL || input_rel->reloptkind == RELOPT_JOINREL ||
(input_rel->reloptkind == RELOPT_UPPER_REL && ifpinfo->stage == UPPERREL_GROUP_AGG));
/*
* We try to create a path below by extending a simple foreign path for
* the underlying base, join, or grouping relation to perform the final
* sort (if has_final_sort) and the LIMIT restriction remotely, which is
* stored into the fdw_private list of the resulting path. (We
* re-estimate the costs of sorting the underlying relation, if
* has_final_sort.)
*
* Assess if it is safe to push down the LIMIT and OFFSET to the remote
* server
*
* If the underlying relation has any local conditions, the LIMIT/OFFSET
* cannot be pushed down.
*/
if (ifpinfo->local_conds) {
return;
}
/*
* Also, the LIMIT/OFFSET cannot be pushed down, if their expressions are
* not safe to remote.
*/
if (!is_foreign_expr(root, input_rel, (Expr *)parse->limitOffset) ||
!is_foreign_expr(root, input_rel, (Expr *)parse->limitCount)) {
return;
}
/* Safe to push down */
fpinfo->pushdown_safe = true;
/* Construct PgFdwPathExtraData */
fpextra = (PgFdwPathExtraData *)palloc0(sizeof(PgFdwPathExtraData));
fpextra->target = extra->targetList;
fpextra->has_final_sort = has_final_sort;
fpextra->has_limit = extra->limit_needed;
fpextra->limit_tuples = extra->limit_tuples;
fpextra->count_est = extra->count_est;
fpextra->offset_est = extra->offset_est;
/*
* Estimate the costs of performing the final sort and the LIMIT
* restriction remotely. If has_final_sort is false, we wouldn't need to
* execute EXPLAIN anymore if use_remote_estimate, since the costs can be
* roughly estimated using the costs we already have for the underlying
* relation, in the same way as when use_remote_estimate is false. Since
* it's pretty expensive to execute EXPLAIN, force use_remote_estimate to
* false in that case.
*/
if (!fpextra->has_final_sort) {
save_use_remote_estimate = ifpinfo->use_remote_estimate;
ifpinfo->use_remote_estimate = false;
}
estimate_path_cost_size(root, input_rel, NIL, pathkeys, fpextra, &rows, &width, &startup_cost, &total_cost);
if (!fpextra->has_final_sort) {
ifpinfo->use_remote_estimate = save_use_remote_estimate;
}
/*
* Build the fdw_private list that will be used by postgresGetForeignPlan.
* Items in the list must match order in enum FdwPathPrivateIndex.
*/
fdw_private = list_make2(makeInteger(has_final_sort), makeInteger(extra->limit_needed));
/*
* Create foreign final path; this gets rid of a no-longer-needed outer
* plan (if any), which makes the EXPLAIN output look cleaner
*/
final_path = create_foreign_upper_path(root, input_rel, extra->targetList, rows, startup_cost,
total_cost, pathkeys, NULL, /* no extra plan */
fdw_private);
/* and add it to the final_rel */
add_path(root, final_rel, (Path *)final_path);
}
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