Horton

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

Amit Langote <amitlangote09@gmail.com>

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From: Amit Langote <amitlangote09@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Andrew Dunstan <andrew@dunslane.net>, David Rowley <dgrowleyml@gmail.com>, John Naylor <john.naylor@enterprisedb.com>, "Jonathan S. Katz" <jkatz@postgresql.org>, Michael Paquier <michael@paquier.xyz>, Nikita Glukhov <n.gluhov@postgrespro.ru>, Peter Geoghegan <pg@bowt.ie>, PostgreSQL-development <pgsql-hackers@postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2022-07-21T15:19:47Z
Lists: pgsql-hackers 
On Thu, Jul 21, 2022 at 11:55 PM Amit Langote <amitlangote09@gmail.com>
wrote:
> On Wed, Jul 20, 2022 at 11:09 PM Amit Langote <amitlangote09@gmail.com>
wrote:
> > On Wed, Jul 20, 2022 at 12:37 AM Andres Freund <andres@anarazel.de>
wrote:
> > > On 2022-07-19 20:40:11 +0900, Amit Langote wrote:
> > > > About that, I was wondering if the blocks in llvm_compile_expr()
need
> > > > to be hand-coded to match what's added in ExecInterpExpr() or if
I've
> > > > missed some tool that can be used instead?
> > >
> > > The easiest way is to just call an external function for the
implementation of
> > > the step. But yes, otherwise you need to handcraft it.
> >
> > Ok, thanks.
> >
> > So I started updating llvm_compile_expr() for handling the new
> > ExprEvalSteps that the patch adds to ExecExprInterp(), but quickly
> > realized that code could have been consolidated into less code, or
> > IOW, into fewer new ExprEvalSteps.  So, I refactored things that way
> > and am now retrying adding the code to llvm_compile_expr() based on
> > new, better consolidated, code.
> >
> > Here's the updated version, without the llvm pieces, in case you'd
> > like to look at it even in this state.  I'll post a version with llvm
> > pieces filled in tomorrow.   (I have merged the different patches into
> > one for convenience.)
>
> And here's a version with llvm pieces filled in.
>
> Because I wrote all of it while not really understanding how the LLVM
> constructs like blocks and branches work, the only reason I think
> those llvm_compile_expr() additions may be correct is that all the
> tests in jsonb_sqljson.sql pass even if I add the following line at
> the top:
>
> set jit_above_cost to 0;

Oh and I did build --with-llvm. :-)


-- 
Thanks, Amit Langote
EDB: http://www.enterprisedb.com
-- 
Thanks, Amit Langote
EDB: http://www.enterprisedb.com

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