Horton

Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: David Rowley <dgrowleyml@gmail.com>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Nikita Glukhov <n.gluhov@postgrespro.ru>, Andrew Dunstan <andrew@dunslane.net>
Date: 2022-06-17T14:33:08Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> The remaining difference looks like it's largely caused by the
> enable_timeout_after(IDLE_STATS_UPDATE_TIMEOUT, ...) introduced as part of the
> pgstats patch. It's only really visible when I pin a single connection pgbench
> to the same CPU core as the server (which gives a ~16% boost here).

> It's not the timeout itself - that we amortize nicely (via 09cf1d522). It's
> that enable_timeout_after() does a GetCurrentTimestamp().

> Not sure yet what the best way to fix that is.

Maybe not queue a new timeout if the old one is still active?

BTW, it looks like that patch also falsified this comment
(postgres.c:4478):

		 * At most one of these timeouts will be active, so there's no need to
		 * worry about combining the timeout.c calls into one.

Maybe fixing that end of things would be a simpler way of buying back
the delta.

> Or we could add a timeout.c API that specifies the timeout?

Don't think that will help: it'd be morally equivalent to
enable_timeout_at(), which also has to do GetCurrentTimestamp().

			regards, tom lane

Commits

  1. JSON_TABLE: Add support for NESTED paths and columns

  2. Add basic JSON_TABLE() functionality

  3. Add SQL/JSON query functions

  4. Add soft error handling to some expression nodes

  5. Adjust populate_record_field() to handle errors softly

  6. Refactor code used by jsonpath executor to fetch variables

  7. Add more SQL/JSON constructor functions

  8. SQL/JSON: support the IS JSON predicate

  9. SQL/JSON: add standard JSON constructor functions

  10. Add static assertion ensuring sizeof(ExprEvalStep) <= 64 bytes

  11. Remove size increase in ExprEvalStep caused by hashed saops

  12. pgstat: reduce timer overhead by leaving timer running.

  13. expression eval: Fix EEOP_JSON_CONSTRUCTOR and EEOP_JSONEXPR size.

  14. SQL/JSON query functions

  15. Speedup ScalarArrayOpExpr evaluation