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Allow extension functions to participate in in-place updates.

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Commit 1dc5ebc90 allowed PL/pgSQL to perform in-place updates
of expanded-object variables that are being updated with
assignments like "x := f(x, ...)".  However this was allowed
only for a hard-wired list of functions f(), since we need to
be sure that f() will not modify the variable if it fails.
It was always envisioned that we should make that extensible,
but at the time we didn't have a good way to do so.  Since
then we've invented the idea of "support functions" to allow
attaching specialized optimization knowledge to functions,
and that is a perfect mechanism for doing this.

Hence, adjust PL/pgSQL to use a support function request instead
of hard-wired logic to decide if in-place update is safe.
Preserve the previous optimizations by creating support functions
for the three functions that were previously hard-wired.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andrey Borodin <x4mmm@yandex-team.ru>
Reviewed-by: Pavel Borisov <pashkin.elfe@gmail.com>
Discussion: https://postgr.es/m/CACxu=vJaKFNsYxooSnW1wEgsAO5u_v1XYBacfVJ14wgJV_PYeg@mail.gmail.com
This commit is contained in:
Tom Lane
2025-02-11 12:49:34 -05:00
parent 6c7251db0c
commit c366d2bdba
9 changed files with 203 additions and 60 deletions
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1
src/tools/pgindent/typedefs.list
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@@ -2804,6 +2804,7 @@ SubscriptionRelState
SummarizerReadLocalXLogPrivate
SupportRequestCost
SupportRequestIndexCondition
SupportRequestModifyInPlace
SupportRequestOptimizeWindowClause
SupportRequestRows
SupportRequestSelectivity