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69f4b9c85f168ae006929eec44fc44d569e846b9
postgresql/src/include/executor/executor.h
Andres Freund 69f4b9c85f Move targetlist SRF handling from expression evaluation to new executor node. 
Evaluation of set returning functions (SRFs_ in the targetlist (like SELECT
generate_series(1,5)) so far was done in the expression evaluation (i.e.
ExecEvalExpr()) and projection (i.e. ExecProject/ExecTargetList) code.

This meant that most executor nodes performing projection, and most
expression evaluation functions, had to deal with the possibility that an
evaluated expression could return a set of return values.

That's bad because it leads to repeated code in a lot of places. It also,
and that's my (Andres's) motivation, made it a lot harder to implement a
more efficient way of doing expression evaluation.

To fix this, introduce a new executor node (ProjectSet) that can evaluate
targetlists containing one or more SRFs. To avoid the complexity of the old
way of handling nested expressions returning sets (e.g. having to pass up
ExprDoneCond, and dealing with arguments to functions returning sets etc.),
those SRFs can only be at the top level of the node's targetlist.  The
planner makes sure (via split_pathtarget_at_srfs()) that SRF evaluation is
only necessary in ProjectSet nodes and that SRFs are only present at the
top level of the node's targetlist. If there are nested SRFs the planner
creates multiple stacked ProjectSet nodes.  The ProjectSet nodes always get
input from an underlying node.

We also discussed and prototyped evaluating targetlist SRFs using ROWS
FROM(), but that turned out to be more complicated than we'd hoped.

While moving SRF evaluation to ProjectSet would allow to retain the old
"least common multiple" behavior when multiple SRFs are present in one
targetlist (i.e.  continue returning rows until all SRFs are at the end of
their input at the same time), we decided to instead only return rows till
all SRFs are exhausted, returning NULL for already exhausted ones.  We
deemed the previous behavior to be too confusing, unexpected and actually
not particularly useful.

As a side effect, the previously prohibited case of multiple set returning
arguments to a function, is now allowed. Not because it's particularly
desirable, but because it ends up working and there seems to be no argument
for adding code to prohibit it.

Currently the behavior for COALESCE and CASE containing SRFs has changed,
returning multiple rows from the expression, even when the SRF containing
"arm" of the expression is not evaluated. That's because the SRFs are
evaluated in a separate ProjectSet node.  As that's quite confusing, we're
likely to instead prohibit SRFs in those places.  But that's still being
discussed, and the code would reside in places not touched here, so that's
a task for later.

There's a lot of, now superfluous, code dealing with set return expressions
around. But as the changes to get rid of those are verbose largely boring,
it seems better for readability to keep the cleanup as a separate commit.

Author: Tom Lane and Andres Freund
Discussion: https://postgr.es/m/20160822214023.aaxz5l4igypowyri@alap3.anarazel.de
2017-01-18 13:40:27 -08:00

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/*-------------------------------------------------------------------------
*
* executor.h
* support for the POSTGRES executor module
*
*
* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* src/include/executor/executor.h
*
*-------------------------------------------------------------------------
*/
#ifndef EXECUTOR_H
#define EXECUTOR_H
#include "catalog/partition.h"
#include "executor/execdesc.h"
#include "nodes/parsenodes.h"
/*
* The "eflags" argument to ExecutorStart and the various ExecInitNode
* routines is a bitwise OR of the following flag bits, which tell the
* called plan node what to expect. Note that the flags will get modified
* as they are passed down the plan tree, since an upper node may require
* functionality in its subnode not demanded of the plan as a whole
* (example: MergeJoin requires mark/restore capability in its inner input),
* or an upper node may shield its input from some functionality requirement
* (example: Materialize shields its input from needing to do backward scan).
*
* EXPLAIN_ONLY indicates that the plan tree is being initialized just so
* EXPLAIN can print it out; it will not be run. Hence, no side-effects
* of startup should occur. However, error checks (such as permission checks)
* should be performed.
*
* REWIND indicates that the plan node should try to efficiently support
* rescans without parameter changes. (Nodes must support ExecReScan calls
* in any case, but if this flag was not given, they are at liberty to do it
* through complete recalculation. Note that a parameter change forces a
* full recalculation in any case.)
*
* BACKWARD indicates that the plan node must respect the es_direction flag.
* When this is not passed, the plan node will only be run forwards.
*
* MARK indicates that the plan node must support Mark/Restore calls.
* When this is not passed, no Mark/Restore will occur.
*
* SKIP_TRIGGERS tells ExecutorStart/ExecutorFinish to skip calling
* AfterTriggerBeginQuery/AfterTriggerEndQuery. This does not necessarily
* mean that the plan can't queue any AFTER triggers; just that the caller
* is responsible for there being a trigger context for them to be queued in.
*
* WITH/WITHOUT_OIDS tell the executor to emit tuples with or without space
* for OIDs, respectively. These are currently used only for CREATE TABLE AS.
* If neither is set, the plan may or may not produce tuples including OIDs.
*/
#define EXEC_FLAG_EXPLAIN_ONLY 0x0001 /* EXPLAIN, no ANALYZE */
#define EXEC_FLAG_REWIND 0x0002 /* need efficient rescan */
#define EXEC_FLAG_BACKWARD 0x0004 /* need backward scan */
#define EXEC_FLAG_MARK 0x0008 /* need mark/restore */
#define EXEC_FLAG_SKIP_TRIGGERS 0x0010 /* skip AfterTrigger calls */
#define EXEC_FLAG_WITH_OIDS 0x0020 /* force OIDs in returned tuples */
#define EXEC_FLAG_WITHOUT_OIDS 0x0040 /* force no OIDs in returned tuples */
#define EXEC_FLAG_WITH_NO_DATA 0x0080 /* rel scannability doesn't matter */
/*
* ExecEvalExpr was formerly a function containing a switch statement;
* now it's just a macro invoking the function pointed to by an ExprState
* node. Beware of double evaluation of the ExprState argument!
*/
#define ExecEvalExpr(expr, econtext, isNull, isDone) \
((*(expr)->evalfunc) (expr, econtext, isNull, isDone))
/* Hook for plugins to get control in ExecutorStart() */
typedef void (*ExecutorStart_hook_type) (QueryDesc *queryDesc, int eflags);
extern PGDLLIMPORT ExecutorStart_hook_type ExecutorStart_hook;
/* Hook for plugins to get control in ExecutorRun() */
typedef void (*ExecutorRun_hook_type) (QueryDesc *queryDesc,
ScanDirection direction,
uint64 count);
extern PGDLLIMPORT ExecutorRun_hook_type ExecutorRun_hook;
/* Hook for plugins to get control in ExecutorFinish() */
typedef void (*ExecutorFinish_hook_type) (QueryDesc *queryDesc);
extern PGDLLIMPORT ExecutorFinish_hook_type ExecutorFinish_hook;
/* Hook for plugins to get control in ExecutorEnd() */
typedef void (*ExecutorEnd_hook_type) (QueryDesc *queryDesc);
extern PGDLLIMPORT ExecutorEnd_hook_type ExecutorEnd_hook;
/* Hook for plugins to get control in ExecCheckRTPerms() */
typedef bool (*ExecutorCheckPerms_hook_type) (List *, bool);
extern PGDLLIMPORT ExecutorCheckPerms_hook_type ExecutorCheckPerms_hook;
/*
* prototypes from functions in execAmi.c
*/
struct Path; /* avoid including relation.h here */
extern void ExecReScan(PlanState *node);
extern void ExecMarkPos(PlanState *node);
extern void ExecRestrPos(PlanState *node);
extern bool ExecSupportsMarkRestore(struct Path *pathnode);
extern bool ExecSupportsBackwardScan(Plan *node);
extern bool ExecMaterializesOutput(NodeTag plantype);
/*
* prototypes from functions in execCurrent.c
*/
extern bool execCurrentOf(CurrentOfExpr *cexpr,
ExprContext *econtext,
Oid table_oid,
ItemPointer current_tid);
/*
* prototypes from functions in execGrouping.c
*/
extern bool execTuplesMatch(TupleTableSlot *slot1,
TupleTableSlot *slot2,
int numCols,
AttrNumber *matchColIdx,
FmgrInfo *eqfunctions,
MemoryContext evalContext);
extern bool execTuplesUnequal(TupleTableSlot *slot1,
TupleTableSlot *slot2,
int numCols,
AttrNumber *matchColIdx,
FmgrInfo *eqfunctions,
MemoryContext evalContext);
extern FmgrInfo *execTuplesMatchPrepare(int numCols,
Oid *eqOperators);
extern void execTuplesHashPrepare(int numCols,
Oid *eqOperators,
FmgrInfo **eqFunctions,
FmgrInfo **hashFunctions);
extern TupleHashTable BuildTupleHashTable(int numCols, AttrNumber *keyColIdx,
FmgrInfo *eqfunctions,
FmgrInfo *hashfunctions,
long nbuckets, Size additionalsize,
MemoryContext tablecxt,
MemoryContext tempcxt, bool use_variable_hash_iv);
extern TupleHashEntry LookupTupleHashEntry(TupleHashTable hashtable,
TupleTableSlot *slot,
bool *isnew);
extern TupleHashEntry FindTupleHashEntry(TupleHashTable hashtable,
TupleTableSlot *slot,
FmgrInfo *eqfunctions,
FmgrInfo *hashfunctions);
/*
* prototypes from functions in execJunk.c
*/
extern JunkFilter *ExecInitJunkFilter(List *targetList, bool hasoid,
TupleTableSlot *slot);
extern JunkFilter *ExecInitJunkFilterConversion(List *targetList,
TupleDesc cleanTupType,
TupleTableSlot *slot);
extern AttrNumber ExecFindJunkAttribute(JunkFilter *junkfilter,
const char *attrName);
extern AttrNumber ExecFindJunkAttributeInTlist(List *targetlist,
const char *attrName);
extern Datum ExecGetJunkAttribute(TupleTableSlot *slot, AttrNumber attno,
bool *isNull);
extern TupleTableSlot *ExecFilterJunk(JunkFilter *junkfilter,
TupleTableSlot *slot);
/*
* prototypes from functions in execMain.c
*/
extern void ExecutorStart(QueryDesc *queryDesc, int eflags);
extern void standard_ExecutorStart(QueryDesc *queryDesc, int eflags);
extern void ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction, uint64 count);
extern void standard_ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction, uint64 count);
extern void ExecutorFinish(QueryDesc *queryDesc);
extern void standard_ExecutorFinish(QueryDesc *queryDesc);
extern void ExecutorEnd(QueryDesc *queryDesc);
extern void standard_ExecutorEnd(QueryDesc *queryDesc);
extern void ExecutorRewind(QueryDesc *queryDesc);
extern bool ExecCheckRTPerms(List *rangeTable, bool ereport_on_violation);
extern void CheckValidResultRel(Relation resultRel, CmdType operation);
extern void InitResultRelInfo(ResultRelInfo *resultRelInfo,
Relation resultRelationDesc,
Index resultRelationIndex,
bool load_partition_check,
Relation partition_root,
int instrument_options);
extern ResultRelInfo *ExecGetTriggerResultRel(EState *estate, Oid relid);
extern bool ExecContextForcesOids(PlanState *planstate, bool *hasoids);
extern void ExecConstraints(ResultRelInfo *resultRelInfo,
TupleTableSlot *slot, TupleTableSlot *orig_slot,
EState *estate);
extern void ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
TupleTableSlot *slot, EState *estate);
extern LockTupleMode ExecUpdateLockMode(EState *estate, ResultRelInfo *relinfo);
extern ExecRowMark *ExecFindRowMark(EState *estate, Index rti, bool missing_ok);
extern ExecAuxRowMark *ExecBuildAuxRowMark(ExecRowMark *erm, List *targetlist);
extern TupleTableSlot *EvalPlanQual(EState *estate, EPQState *epqstate,
Relation relation, Index rti, int lockmode,
ItemPointer tid, TransactionId priorXmax);
extern HeapTuple EvalPlanQualFetch(EState *estate, Relation relation,
int lockmode, LockWaitPolicy wait_policy, ItemPointer tid,
TransactionId priorXmax);
extern void EvalPlanQualInit(EPQState *epqstate, EState *estate,
Plan *subplan, List *auxrowmarks, int epqParam);
extern void EvalPlanQualSetPlan(EPQState *epqstate,
Plan *subplan, List *auxrowmarks);
extern void EvalPlanQualSetTuple(EPQState *epqstate, Index rti,
HeapTuple tuple);
extern HeapTuple EvalPlanQualGetTuple(EPQState *epqstate, Index rti);
extern void ExecSetupPartitionTupleRouting(Relation rel,
PartitionDispatch **pd,
ResultRelInfo **partitions,
TupleConversionMap ***tup_conv_maps,
TupleTableSlot **partition_tuple_slot,
int *num_parted, int *num_partitions);
extern int ExecFindPartition(ResultRelInfo *resultRelInfo,
PartitionDispatch *pd,
TupleTableSlot *slot,
EState *estate);
#define EvalPlanQualSetSlot(epqstate, slot) ((epqstate)->origslot = (slot))
extern void EvalPlanQualFetchRowMarks(EPQState *epqstate);
extern TupleTableSlot *EvalPlanQualNext(EPQState *epqstate);
extern void EvalPlanQualBegin(EPQState *epqstate, EState *parentestate);
extern void EvalPlanQualEnd(EPQState *epqstate);
/*
* prototypes from functions in execProcnode.c
*/
extern PlanState *ExecInitNode(Plan *node, EState *estate, int eflags);
extern TupleTableSlot *ExecProcNode(PlanState *node);
extern Node *MultiExecProcNode(PlanState *node);
extern void ExecEndNode(PlanState *node);
extern bool ExecShutdownNode(PlanState *node);
/*
* prototypes from functions in execQual.c
*/
extern Datum GetAttributeByNum(HeapTupleHeader tuple, AttrNumber attrno,
bool *isNull);
extern Datum GetAttributeByName(HeapTupleHeader tuple, const char *attname,
bool *isNull);
extern Tuplestorestate *ExecMakeTableFunctionResult(ExprState *funcexpr,
ExprContext *econtext,
MemoryContext argContext,
TupleDesc expectedDesc,
bool randomAccess);
extern Datum ExecMakeFunctionResultSet(FuncExprState *fcache,
ExprContext *econtext,
bool *isNull,
ExprDoneCond *isDone);
extern Datum ExecEvalExprSwitchContext(ExprState *expression, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone);
extern ExprState *ExecInitExpr(Expr *node, PlanState *parent);
extern ExprState *ExecPrepareExpr(Expr *node, EState *estate);
extern bool ExecQual(List *qual, ExprContext *econtext, bool resultForNull);
extern int ExecTargetListLength(List *targetlist);
extern int ExecCleanTargetListLength(List *targetlist);
extern TupleTableSlot *ExecProject(ProjectionInfo *projInfo,
ExprDoneCond *isDone);
/*
* prototypes from functions in execScan.c
*/
typedef TupleTableSlot *(*ExecScanAccessMtd) (ScanState *node);
typedef bool (*ExecScanRecheckMtd) (ScanState *node, TupleTableSlot *slot);
extern TupleTableSlot *ExecScan(ScanState *node, ExecScanAccessMtd accessMtd,
ExecScanRecheckMtd recheckMtd);
extern void ExecAssignScanProjectionInfo(ScanState *node);
extern void ExecAssignScanProjectionInfoWithVarno(ScanState *node, Index varno);
extern void ExecScanReScan(ScanState *node);
/*
* prototypes from functions in execTuples.c
*/
extern void ExecInitResultTupleSlot(EState *estate, PlanState *planstate);
extern void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate);
extern TupleTableSlot *ExecInitExtraTupleSlot(EState *estate);
extern TupleTableSlot *ExecInitNullTupleSlot(EState *estate,
TupleDesc tupType);
extern TupleDesc ExecTypeFromTL(List *targetList, bool hasoid);
extern TupleDesc ExecCleanTypeFromTL(List *targetList, bool hasoid);
extern TupleDesc ExecTypeFromExprList(List *exprList);
extern void ExecTypeSetColNames(TupleDesc typeInfo, List *namesList);
extern void UpdateChangedParamSet(PlanState *node, Bitmapset *newchg);
typedef struct TupOutputState
{
TupleTableSlot *slot;
DestReceiver *dest;
} TupOutputState;
extern TupOutputState *begin_tup_output_tupdesc(DestReceiver *dest,
TupleDesc tupdesc);
extern void do_tup_output(TupOutputState *tstate, Datum *values, bool *isnull);
extern void do_text_output_multiline(TupOutputState *tstate, const char *txt);
extern void end_tup_output(TupOutputState *tstate);
/*
* Write a single line of text given as a C string.
*
* Should only be used with a single-TEXT-attribute tupdesc.
*/
#define do_text_output_oneline(tstate, str_to_emit) \
do { \
Datum values_[1]; \
bool isnull_[1]; \
values_[0] = PointerGetDatum(cstring_to_text(str_to_emit)); \
isnull_[0] = false; \
do_tup_output(tstate, values_, isnull_); \
pfree(DatumGetPointer(values_[0])); \
} while (0)
/*
* prototypes from functions in execUtils.c
*/
extern EState *CreateExecutorState(void);
extern void FreeExecutorState(EState *estate);
extern ExprContext *CreateExprContext(EState *estate);
extern ExprContext *CreateStandaloneExprContext(void);
extern void FreeExprContext(ExprContext *econtext, bool isCommit);
extern void ReScanExprContext(ExprContext *econtext);
#define ResetExprContext(econtext) \
MemoryContextReset((econtext)->ecxt_per_tuple_memory)
extern ExprContext *MakePerTupleExprContext(EState *estate);
/* Get an EState's per-output-tuple exprcontext, making it if first use */
#define GetPerTupleExprContext(estate) \
((estate)->es_per_tuple_exprcontext ? \
(estate)->es_per_tuple_exprcontext : \
MakePerTupleExprContext(estate))
#define GetPerTupleMemoryContext(estate) \
(GetPerTupleExprContext(estate)->ecxt_per_tuple_memory)
/* Reset an EState's per-output-tuple exprcontext, if one's been created */
#define ResetPerTupleExprContext(estate) \
do { \
if ((estate)->es_per_tuple_exprcontext) \
ResetExprContext((estate)->es_per_tuple_exprcontext); \
} while (0)
extern void ExecAssignExprContext(EState *estate, PlanState *planstate);
extern void ExecAssignResultType(PlanState *planstate, TupleDesc tupDesc);
extern void ExecAssignResultTypeFromTL(PlanState *planstate);
extern TupleDesc ExecGetResultType(PlanState *planstate);
extern ProjectionInfo *ExecBuildProjectionInfo(List *targetList,
ExprContext *econtext,
TupleTableSlot *slot,
TupleDesc inputDesc);
extern void ExecAssignProjectionInfo(PlanState *planstate,
TupleDesc inputDesc);
extern void ExecFreeExprContext(PlanState *planstate);
extern void ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc);
extern void ExecAssignScanTypeFromOuterPlan(ScanState *scanstate);
extern bool ExecRelationIsTargetRelation(EState *estate, Index scanrelid);
extern Relation ExecOpenScanRelation(EState *estate, Index scanrelid, int eflags);
extern void ExecCloseScanRelation(Relation scanrel);
extern void RegisterExprContextCallback(ExprContext *econtext,
ExprContextCallbackFunction function,
Datum arg);
extern void UnregisterExprContextCallback(ExprContext *econtext,
ExprContextCallbackFunction function,
Datum arg);
/*
* prototypes from functions in execIndexing.c
*/
extern void ExecOpenIndices(ResultRelInfo *resultRelInfo, bool speculative);
extern void ExecCloseIndices(ResultRelInfo *resultRelInfo);
extern List *ExecInsertIndexTuples(TupleTableSlot *slot, ItemPointer tupleid,
EState *estate, bool noDupErr, bool *specConflict,
List *arbiterIndexes);
extern bool ExecCheckIndexConstraints(TupleTableSlot *slot, EState *estate,
ItemPointer conflictTid, List *arbiterIndexes);
extern void check_exclusion_constraint(Relation heap, Relation index,
IndexInfo *indexInfo,
ItemPointer tupleid,
Datum *values, bool *isnull,
EState *estate, bool newIndex);
#endif /* EXECUTOR_H */
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