Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Peter Geoghegan <pg@bowt.ie>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Nikita Glukhov <n.gluhov@postgrespro.ru>, Andrew Dunstan <andrew@dunslane.net>
Date: 2022-06-17T05:22:28Z
Lists: pgsql-hackers

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Hi,

On 2022-06-17 16:53:31 +1200, David Rowley wrote:
> On Fri, 17 Jun 2022 at 15:33, Peter Geoghegan <pg@bowt.ie> wrote:
> > Have you tried this with the insert benchmark [1]?
> 
> I was mostly focusing on the performance of the hashed saop feature
> after having removed the additional fields that pushed ExprEvalStep
> over 64 bytes in 14.
> 
> I agree it would be good to do further benchmarking to see if there's
> anything else that's snuck into 15 that's slowed that benchmark down,
> but we can likely work on that after we get the ExprEvalStep size back
> to 64 bytes again.

I did reproduce a regression between 14 and 15, using both pgbench -Mprepared
-S (scale 1) and TPC-H Q01 (scale 5). Between 7-10% - not good, particularly
that that's not been found so far. Fixing the json size issue gets that down
to ~2%. Not sure what that's caused by yet.

Greetings,

Andres Freund

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