From: | Melanie Plageman <melanieplageman(at)gmail(dot)com> |
---|---|
To: | Alexander Korotkov <akorotkov(at)postgresql(dot)org> |
Cc: | pgsql-committers(at)lists(dot)postgresql(dot)org |
Subject: | Re: pgsql: Transform OR clauses to ANY expression |
Date: | 2024-04-07 22:35:21 |
Message-ID: | CAAKRu_b4SXNW4GAM0bv3e6wcL5ODSXg1ZdRCn6uyLLjSPbveBg@mail.gmail.com |
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On Sun, Apr 7, 2024 at 6:28 PM Alexander Korotkov
<akorotkov(at)postgresql(dot)org> wrote:
>
> Transform OR clauses to ANY expression
>
> Replace (expr op C1) OR (expr op C2) ... with expr op ANY(ARRAY[C1, C2, ...])
> on the preliminary stage of optimization when we are still working with the
> expression tree.
>
> Here Cn is a n-th constant expression, 'expr' is non-constant expression, 'op'
> is an operator which returns boolean result and has a commuter (for the case
> of reverse order of constant and non-constant parts of the expression,
> like 'Cn op expr').
>
> Sometimes it can lead to not optimal plan. This is why there is a
> or_to_any_transform_limit GUC. It specifies a threshold value of length of
> arguments in an OR expression that triggers the OR-to-ANY transformation.
> Generally, more groupable OR arguments mean that transformation will be more
> likely to win than to lose.
I'm getting this warning now
/src/backend/optimizer/prep/prepqual.c:582:33: warning: declaration of
‘lc__state’ shadows a previous local [-Wshadow=compatible-local]
582 | foreach(lc, entry->consts)
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