Re: How to use SPI_saveplan

Tom Lane wrote:
> Jack Orenstein <jao@geophile.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