| From: | Nikolay Samokhvalov <samokhvalov(at)gmail(dot)com> |
|---|---|
| To: | Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: huge SubtransSLRU and SubtransBuffer wait_event |
| Date: | 2024-02-02 10:04:02 |
| Message-ID: | CANNMO++EdBcR7yHMp4hsYO3NcyKwj_VFy4jzuqA0AGeCfn2XjA@mail.gmail.com |
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| Lists: | pgsql-performance |
On Thu, Feb 1, 2024 at 04:42 Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
> Today, the only feasible solution is not to create more than 64
> subtransactions
> (savepoints or PL/pgSQL EXCEPTION clauses) per transaction.
Sometimes, a single subtransaction is enough to experience a bad
SubtransSLRU spike:
https://postgres.ai/blog/20210831-postgresql-subtransactions-considered-harmful#problem-4-subtrans-slru-overflow
I think 64+ nesting level is quite rare, but this kind of problem that hits
you when you have high XID growth (lots of writes) + long-running
transaction is quite easy to bump into. Or this case involving
MultiXactIDs:
https://buttondown.email/nelhage/archive/notes-on-some-postgresql-implementation-details/
Nik
>
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