Re: Does PostgreSQL do bind-peeking? Is `col like '%'` optimized-away by the planner?

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От David G. Johnston
Тема Re: Does PostgreSQL do bind-peeking? Is `col like '%'` optimized-away by the planner?
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Msg-id CAKFQuwZA6iKQOQWSDu8MY2NCYhB0RhQpmRCKakLUsVhwAEOxfg@mail.gmail.com
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Ответ на Does PostgreSQL do bind-peeking? Is `col like '%'` optimized-away by the planner?  (Dominique Devienne <ddevienne@gmail.com>)
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On Fri, Jan 21, 2022 at 9:36 AM Dominique Devienne <ddevienne@gmail.com> wrote:

for the various cases of empty argN strings, or does the planner do
*bind-peeking*, and thus a single prepared statement would do the job,
and still have different plans used depending on the actual binds?

I'm assuming PostgreSQL does bind-peeking like Oracle, but I don't
know, and I've never read anything yet about that.


A prepared statement either generates a custom plan and, as a side-effect, does bind-peeking, or it uses the single prepared plan it has established and executes that.  It doesn't use bind-peeking to decide among multiple saved prepared plans. There is more to it than that, like a 5 custom plan threshold before abandoning bind-peeking (I think I got that right...).

David J.

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