| From: | "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> |
|---|---|
| To: | 'David Rowley' <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, "Imai, Yoshikazu" <imai(dot)yoshikazu(at)jp(dot)fujitsu(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | RE: Speed up transaction completion faster after many relations are accessed in a transaction |
| Date: | 2019-07-22 04:34:59 |
| Message-ID: | 0A3221C70F24FB45833433255569204D1FC83A75@G01JPEXMBYT05 |
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| Lists: | pgsql-hackers |
From: David Rowley [mailto:david(dot)rowley(at)2ndquadrant(dot)com]
> For the use case we've been measuring with partitioned tables and the
> generic plan generation causing a sudden spike in the number of
> obtained locks, then having plan_cache_mode = force_custom_plan will
> cause the lock table not to become bloated. I'm not sure there's
> anything interesting to measure there.
I meant the difference between the following two cases, where the query only touches one partition (e.g. SELECT ... WHERE pkey = value):
* plan_cache_mode=force_custom_plan: LocalLockHash won't bloat. The query execution time is steady.
* plan_cache_mode=auto: LocalLockHash bloats on the sixth execution due to the creation of the generic plan. The generic plan is not adopted because its cost is high. Later executions of the query will suffer from the bloat until the 1006th execution when LocalLockHash is shrunk.
Depending on the number of transactions and what each transaction does, I thought the difference will be noticeable or not.
Regards
Takayuki Tsunakawa
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