From: | Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> |
---|---|
To: | torikoshia <torikoshia(at)oss(dot)nttdata(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [doc] plan invalidation when statistics are update |
Date: | 2020-11-24 14:14:57 |
Message-ID: | 0e55d428-9156-8ea0-a480-03d4bd3b3277@oss.nttdata.com |
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Lists: | pgsql-hackers |
On 2020/11/19 14:33, torikoshia wrote:
> On 2020-11-18 11:35, Fujii Masao wrote:
>
> Thanks for your comment!
>
>> On 2020/11/18 11:04, torikoshia wrote:
>>> Hi,
>>>
>>> AFAIU, when the planner statistics are updated, generic plans are invalidated and PostgreSQL recreates. However, the manual doesn't seem to explain it explicitly.
>>>
>>> https://www.postgresql.org/docs/devel/sql-prepare.html
>>>
>>> I guess this case is included in 'whenever database objects used in the statement have definitional (DDL) changes undergone', but I feel it's hard to infer.
>>>
>>> Since updates of the statistics can often happen, how about describing this case explicitly like an attached patch?
>>
>> +1 to add that note.
>>
>> - statement. Also, if the value of <xref linkend="guc-search-path"/> changes
>> + statement. For example, when the planner statistics of the statement
>> + are updated, <productname>PostgreSQL</productname> re-analyzes and
>> + re-plans the statement.
>>
>> I don't think "For example," is necessary.
>>
>> "planner statistics of the statement" sounds vague? Does the statement
>> is re-analyzed and re-planned only when the planner statistics of database
>> objects used in the statement are updated? If yes, we should describe
>> that to make the note a bit more explicitly?
>
> Yes. As far as I confirmed, updating statistics which are not used in
> prepared statements doesn't trigger re-analyze and re-plan.
>
> Since plan invalidations for DDL changes and statistcal changes are caused
> by PlanCacheRelCallback(Oid 'relid'), only the prepared statements using
> 'relid' relation seem invalidated.>
> Attached updated patch.
Thanks for confirming that and updating the patch!
Barring any objection, I will commit the patch.
Regards,
--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION
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