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Add SupportRequestInlineInFrom planner support request.

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This request allows a support function to replace a function call
appearing in FROM (typically a set-returning function) with an
equivalent SELECT subquery.  The subquery will then be subject
to the planner's usual optimizations, potentially allowing a much
better plan to be generated.  While the planner has long done this
automatically for simple SQL-language functions, it's now possible
for extensions to do it for functions outside that group.
Notably, this could be useful for functions that are presently
implemented in PL/pgSQL and work by generating and then EXECUTE'ing
a SQL query.

Author: Paul A Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/09de6afa-c33d-4d94-a5cb-afc6cea0d2bb@illuminatedcomputing.com
This commit is contained in:
Tom Lane
2025-11-22 19:33:34 -05:00
parent c0bc9af151
commit b140c8d7a3
9 changed files with 511 additions and 171 deletions
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30
src/include/nodes/supportnodes.h
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@@ -39,6 +39,8 @@ typedef struct PlannerInfo PlannerInfo; /* avoid including pathnodes.h here */
typedef struct IndexOptInfo IndexOptInfo;
typedef struct SpecialJoinInfo SpecialJoinInfo;
typedef struct WindowClause WindowClause;
typedef struct RangeTblFunction RangeTblFunction; /* ditto for parsenodes.h */
typedef struct HeapTupleData *HeapTuple; /* and htup.h too */
/*
* The Simplify request allows the support function to perform plan-time
@@ -69,6 +71,34 @@ typedef struct SupportRequestSimplify
FuncExpr *fcall; /* Function call to be simplified */
} SupportRequestSimplify;
/*
* The InlineInFrom request allows the support function to perform plan-time
* simplification of a call to its target function that appears in FROM.
* The rules for this are sufficiently different from ordinary expressions
* that it's best to make this a separate request from Simplify.
*
* The planner's PlannerInfo "root" is typically not needed, but can be
* consulted if it's necessary to obtain info about Vars present in
* the given node tree. Beware that root could be NULL in some usages.
*
* "rtfunc" will be a RangeTblFunction node for the support function's target
* function. The call appeared alone (and without ORDINALITY) in FROM.
*
* "proc" will be the HeapTuple for the pg_proc row of the target function.
*
* The result should be a semantically-equivalent SELECT Query tree,
* or NULL if no simplification could be performed. The tree must have
* been passed through parse analysis and rewrite.
*/
typedef struct SupportRequestInlineInFrom
{
NodeTag type;
PlannerInfo *root; /* Planner's infrastructure */
RangeTblFunction *rtfunc; /* Function call to be simplified */
HeapTuple proc; /* Function definition from pg_proc */
} SupportRequestInlineInFrom;
/*
* The Selectivity request allows the support function to provide a
* selectivity estimate for a function appearing at top level of a WHERE

4
src/include/optimizer/clauses.h
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@@ -50,8 +50,8 @@ extern int NumRelids(PlannerInfo *root, Node *clause);
extern void CommuteOpExpr(OpExpr *clause);
extern Query *inline_set_returning_function(PlannerInfo *root,
RangeTblEntry *rte);
extern Query *inline_function_in_from(PlannerInfo *root,
RangeTblEntry *rte);
extern Bitmapset *pull_paramids(Expr *expr);