Re: Is it useful to record whether plans are generic or custom?

From: Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>
To: Tatsuro Yamada <tatsuro(dot)yamada(dot)tf(at)nttcom(dot)co(dot)jp>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, torikoshia <torikoshia(at)oss(dot)nttdata(dot)com>
Cc: legrand legrand <legrand_legrand(at)hotmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Is it useful to record whether plans are generic or custom?
Date: 2020-12-04 05:29:35
Message-ID: 9554b3d2-b9a9-df6e-d7e0-c988c7ea02ce@oss.nttdata.com
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On 2020/11/30 15:24, Tatsuro Yamada wrote:
> Hi Torikoshi-san,
>
>
>> In this patch, exposing new columns is mandatory, but I think
>> it's better to make it optional by adding a GUC something
>> like 'pgss.track_general_custom_plans.
>>
>> I also feel it makes the number of columns too many.
>> Just adding the total time may be sufficient.
>
>
> I think this feature is useful for DBA. So I hope that it gets
> committed to PG14. IMHO, many columns are Okay because DBA can
> select specific columns by their query.
> Therefore, it would be better to go with the current design.

But that design may waste lots of memory. No? For example, when
plan_cache_mode=force_custom_plan, the memory used for the columns
for generic plans is not used.

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION

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