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Keep track of what RTIs a Result node is scanning.

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Result nodes now include an RTI set, which is only non-NULL when they
have no subplan, and is taken from the relid set of the RelOptInfo that
the Result is generating. ExplainPreScanNode now takes notice of these
RTIs, which means that a few things get schema-qualified in the
regression tests that previously did not. This makes the output more
consistent between cases where some part of the plan tree is replaced by
a Result node and those where this does not happen.

Likewise, pg_overexplain's EXPLAIN (RANGE_TABLE) now displays the RTIs
stored in a Result node just as it already does for other RTI-bearing
node types.

Result nodes also now include a result_reason, which tells us something
about why the Result node was inserted.  Using that information, EXPLAIN
now emits, where relevant, a "Replaces" line describing the origin of
a Result node.

The purpose of these changes is to allow code that inspects a Plan
tree to understand the origin of Result nodes that appear therein.

Discussion: http://postgr.es/m/CA+TgmoYeUZePZWLsSO+1FAN7UPePT_RMEZBKkqYBJVCF1s60=w@mail.gmail.com
Reviewed-by: Alexandra Wang <alexandra.wang.oss@gmail.com>
Reviewed-by: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Junwang Zhao <zhjwpku@gmail.com>
This commit is contained in:
Robert Haas
2025-09-23 09:07:55 -04:00
parent a48d1ef586
commit f2bae51dfd
27 changed files with 571 additions and 271 deletions
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22
src/include/nodes/plannodes.h
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@ -252,6 +252,20 @@ typedef struct Plan
#define outerPlan(node) (((Plan *)(node))->lefttree)
/* ----------------
* ResultType -
* Classification of Result nodes
* ----------------
*/
typedef enum ResultType
{
RESULT_TYPE_GATING, /* project or one-time-filter outer plan */
RESULT_TYPE_SCAN, /* replace empty scan */
RESULT_TYPE_JOIN, /* replace empty join */
RESULT_TYPE_UPPER, /* replace degenerate upper rel */
RESULT_TYPE_MINMAX /* implement minmax aggregate */
} ResultType;
/* ----------------
* Result node -
* If no outer plan, evaluate a variable-free targetlist.
@ -261,12 +275,20 @@ typedef struct Plan
* If resconstantqual isn't NULL, it represents a one-time qualification
* test (i.e., one that doesn't depend on any variables from the outer plan,
* so needs to be evaluated only once).
*
* relids identifies the relation for which this Result node is generating the
* tuples. When subplan is not NULL, it should be empty: this node is not
* generating anything in that case, just acting on tuples generated by the
* subplan. Otherwise, it contains the relids of the planner relation that
* the Result represents.
* ----------------
*/
typedef struct Result
{
Plan plan;
ResultType result_type;
Node *resconstantqual;
Bitmapset *relids;
} Result;
/* ----------------