From: | wd <wd(at)wdicc(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | PostgreSQL General <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Weird explain output |
Date: | 2013-02-04 08:35:51 |
Message-ID: | CABexzmhRDSkGB+4sN+r7fsZHVQ+Otc77ybXy8CocHOJjW6HGnw@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
Thanks for your reply.
On Mon, Feb 4, 2013 at 3:48 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> You're worrying about the wrong thing entirely. The right thing to be
> worrying about is why are some of those row estimates off by four orders
> of magnitude, and what you can do to fix that. The planner will never
> deliver sane plans when its estimates are so far off from reality.
>
>
You mean the rows from explain is bigger then the rows real returned?
It caused by a sub query with a filter like ( a and b ) or ( c and d ),
I've tried to create a temp table for it, the explained rows and the real
rows will similarly.
Here is the full output, http://explain.depesz.com/s/M7oo
> From my perspective, you snipped all the interesting parts of this
> output, because the misestimation is evidently happening somewhere down
> in there.
>
> regards, tom lane
>
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