Re: Seeking reason behind performance gain in 12 with HashAggregate

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От	Shira Bezalel
Тема	Re: Seeking reason behind performance gain in 12 with HashAggregate
Дата	14 января 2020 г. 00:45:55
Msg-id	CAE0KEwEyMhS85CcUJyom6QQ4VtSn6bwxiz-VoBpRe4DWw-12CQ@mail.gmail.com обсуждение исходный текст
Ответ на	Re: Seeking reason behind performance gain in 12 with HashAggregate (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Список	pgsql-performance

Дерево обсуждения

Thanks Tomas. I ran a vacuum full on the 9.6 table -- still no difference in the query plan. The shared buffers hit went up slightly to 36069.

Shira

On Mon, Jan 13, 2020 at 1:12 PM Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:

On Mon, Jan 13, 2020 at 12:44:14PM -0800, Shira Bezalel wrote:
>Hi Michael,
>
>I appreciate your question. I ran a vacuum analyze on the 9.6 table and it
>yielded no difference. Same number of buffers were read, same query plan.
>

VACUUM ANALYZE won't shrink the table - the number of buffers will be
exactly the same. You need to do VACUUM FULL, but be careful as that
acquires exclusive lock on the table.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services