From: | Danny Shemesh <dany74q(at)gmail(dot)com> |
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To: | pgsql-general(at)postgresql(dot)org |
Subject: | Showing alternative query planner plans with explain ? |
Date: | 2022-05-29 11:49:48 |
Message-ID: | CAFZC=QpMZutOUnJATYzLiuvM9CAk7UPpWmnZX6uGXxgHYSE6nw@mail.gmail.com |
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Lists: | pgsql-general |
Hey all !
I'm currently optimizing queries and indices on a relatively large dataset;
one of the frequent questions I seem to ask myself is why the planner
chooses plan A over B.
Reading the docs, blogs, stack exchange posts, wiki, ... helps in trying to
tinker with the query or indices in a way that either A will be
discouraged, or B will be favoured, so I'd be more informed on why one was
chosen over the other and which is empirically better for a given dataset.
A tool I seem to be missing, and I wondered if such exists, is to have the
planner output alternative plans for a given query, i.e. to say, give me
the x top plans sorted by cost - I believe this would help shed some light
on the internal state machine and subsequent tinkering less
trial-and-error-ish.
Is there any way to achieve the above ?
Thanks a ton,
Danny
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