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Silence complaints about leaks in PlanCacheComputeResultDesc.

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CompleteCachedPlan intentionally doesn't worry about small
leaks from PlanCacheComputeResultDesc.  However, Valgrind
knows nothing of engineering tradeoffs and complains anyway.
Silence it by doing things the hard way if USE_VALGRIND.

I don't really love this patch, because it makes the handling
of plansource->resultDesc different from the handling of query
dependencies and search_path just above, which likewise are willing
to accept small leaks into the cached plan's context.  However,
those cases aren't provoking Valgrind complaints.  (Perhaps in a
CLOBBER_CACHE_ALWAYS build, they would?)  For the moment, this
makes the src/pl/plpgsql tests leak-free according to Valgrind.

Author: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/285483.1746756246@sss.pgh.pa.us
This commit is contained in:
Tom Lane 2025-08-02 19:44:10 -04:00
parent 7f6ededa76
commit b102c8c473
1 changed files with 18 additions and 3 deletions
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21
src/backend/utils/cache/plancache.c vendored
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@ -463,8 +463,7 @@ CompleteCachedPlan(CachedPlanSource *plansource,
/*
* Save the final parameter types (or other parameter specification data)
* into the source_context, as well as our other parameters. Also save
* the result tuple descriptor.
* into the source_context, as well as our other parameters.
*/
MemoryContextSwitchTo(source_context);
@ -480,9 +479,25 @@ CompleteCachedPlan(CachedPlanSource *plansource,
plansource->parserSetupArg = parserSetupArg;
plansource->cursor_options = cursor_options;
plansource->fixed_result = fixed_result;
plansource->resultDesc = PlanCacheComputeResultDesc(querytree_list);
/*
* Also save the result tuple descriptor. PlanCacheComputeResultDesc may
* leak some cruft; normally we just accept that to save a copy step, but
* in USE_VALGRIND mode be tidy by running it in the caller's context.
*/
#ifdef USE_VALGRIND
MemoryContextSwitchTo(oldcxt);
plansource->resultDesc = PlanCacheComputeResultDesc(querytree_list);
if (plansource->resultDesc)
{
MemoryContextSwitchTo(source_context);
plansource->resultDesc = CreateTupleDescCopy(plansource->resultDesc);
MemoryContextSwitchTo(oldcxt);
}
#else
plansource->resultDesc = PlanCacheComputeResultDesc(querytree_list);
MemoryContextSwitchTo(oldcxt);
#endif
plansource->is_complete = true;
plansource->is_valid = true;