From: | Jack Orenstein <jao(at)geophile(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: How to use SPI_saveplan |
Date: | 2006-09-10 02:20:55 |
Message-ID: | 45037687.3070802@geophile.com |
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Lists: | pgsql-general |
Tom Lane wrote:
> Jack Orenstein <jao(at)geophile(dot)com> writes:
>> I'm missing something very basic. If I do this:
>
>> Datum foobar(PG_FUNCTION_ARGS)
>> {
>> ...
>> void* plan = SPI_prepare(...);
>> void* saved_plan = SPI_saveplan(plan);
>> ...
>> }
>
>> then how can I access the saved plan in a later invocation of foobar?
>
> It's up to you to save the pointer somewhere where you can find it again
> when you need it. If there's only one interesting plan, use a static
> variable. Otherwise, you'll need some sort of data structure to map
> from what-you-need to the-plan-that-does-it. You can find examples of
> these approaches in the PG sources (from memory, ruleutils.c has some
> examples of the former approach while ri_triggers.c does the latter).
OK, that makes sense. It was use of the term "local variable" that threw
me.
Assigning SPI_prepare output to a local makes sense. Assigning
SPI_saveplan output to a static makes sense. But I don't see
the point in assigning SPI_saveplan output to a local, yet
that's what one case the doc specifically mentions.
Jack Orenstein
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