Re: BUG #15609: synchronous_commit=off insert performance regressionwith secondary indexes

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От Saul, Jean Paolo
Тема Re: BUG #15609: synchronous_commit=off insert performance regressionwith secondary indexes
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Msg-id CA+73ANdw+2H9dcqFPEhhkwB_H2BOfX0hMv4YFoxG18ANPjE2Ng@mail.gmail.com
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Ответ на Re: BUG #15609: synchronous_commit=off insert performance regressionwith secondary indexes  (Bruce Momjian <bruce@momjian.us>)
Ответы Re: BUG #15609: synchronous_commit=off insert performance regressionwith secondary indexes  (Bruce Momjian <bruce@momjian.us>)
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Hi Bruce,

Thank you for that info. We will likely migrate our boolean indexes (and possibly all our low cardinality indexes) to hash after we move to PG11.

How would I know if the PostgreSQL team will be investigating this possible regression issue?
OR can someone help me how to further identify the root cause in the code?

It would be nice if we can patch this out, or at least find the reasoning for the slowness.
Does btree somehow have a global lock on a leaf node when it's being modified?

Sorry for all the questions.


Cheers,

Paolo


On Fri, 1 Feb 2019 at 03:36, Bruce Momjian <bruce@momjian.us> wrote:
On Thu, Jan 31, 2019 at 04:08:39PM +1300, Saul, Jean Paolo wrote:
> Additional tests replacing BTREE indexes with HASH indexes indicate that hash
> indexes do not suffer from low-cardinality performance regression.
> However I cannot use hash indexes in our systems as they are discouraged.

Hash indexes are crash safe since PG 10 so their use is no longer
discouraged, at least from a project perspective.

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