Re: ORDER BY with plpgsql parameter - Mailing list pgsql-general

From Thomas Schoen
Subject Re: ORDER BY with plpgsql parameter
Date
Msg-id 200406021812.38704.t.schoen@vitrado.de
Whole thread Raw
In response to Re: ORDER BY with plpgsql parameter  (Richard Huxton <dev@archonet.com>)
Responses Re: ORDER BY with plpgsql parameter  (DeJuan Jackson <djackson@speedfc.com>)
Re: ORDER BY with plpgsql parameter  (Richard Huxton <dev@archonet.com>)
List pgsql-general
> You want to build a dynamic query (sorted in different ways depending on
> a function parameter).
yes.

>
> You don't want to use the dynamic query statement (EXECUTE).
yes, because it seems to me, that "for in execute" is slower than the direct
way. Is that right?
>
> The whole point of plpgsql is that the queries can be compiled and
> pre-planned. If you want to change the sorting then that implies a
> different plan, which implies using the dynamic query feature.
OK, does that mean, that it is no difference in performance whether i use "FOR
IN EXECUTE" or two different functions with different sorting?

>
> What you want to do is possible if you use one of the interpreted
> languages, e.g. pltcl/plperl (plphp?). Of course, that means none of
> your query plans get compiled.
What happens to the query plan if i use function-parameters in the where
clause of my statement? Is the function recompiled then?

Conclusion: if i want to sort inside the functions depending on function
parameters, the best way to do it is using "FOR IN EXECUTE"??
Is that right?

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