From: | Ernst-Georg Schmid <pgchem(at)tuschehund(dot)de> |
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To: | "pgsql-interfaces(at)postgresql(dot)org" <pgsql-interfaces(at)postgresql(dot)org> |
Subject: | Re: C trigger significantly slower than PL/pgSQL? |
Date: | 2023-04-14 17:39:20 |
Message-ID: | 8306edcc-8458-44b3-485b-0725de3c7743@tuschehund.de |
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Lists: | pgsql-interfaces |
> Yeah, there's your problem. Each time through the trigger, that query
> is being parsed, planned, and executed from scratch. plpgsql knows
> how to cache the planned statement, so it's doing less work per-call.
Hello again,
thank you for your help.
I have now used SPI_prepare() and SPI_keepplan() to cache the plan in a
static variable - and now it performs exactly like the PL/pgSQL version.
Which also probably means that either the Trigger is so trivial that C
makes no difference, or the observed TPS limit comes from somewhere else.
I have still a follow-up question, though. Since I'm not calling
SPI_freeplan(), the cached plan lives forever, right? Which is no
problem, since the trigger does the same statement over and over. But
does this generate a memory leak? Or is the saved plan tied to the
session and is deallocated when the session ends?
best regards
Ernst-Georg
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