Horton

Re: WIP: Faster Expression Processing v4

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2017-03-24T00:43:23Z
Lists: pgsql-hackers 
Hi,m

On 2017-03-23 17:40:55 -0400, Tom Lane wrote:
> Stylistic thought ... I am wondering if it wouldn't be a good idea
> to replace EEOP_CASE_WHEN_STEP, EEOP_CASE_THEN_STEP, EEOP_COALESCE,
> and EEOP_ARRAYREF_CHECKINPUT with instructions defined in a less
> usage-dependent way as
> 
> 	EEOP_JUMP		unconditional jump
> 	EEOP_JUMP_IF_NULL	jump if step result is null
> 	EEOP_JUMP_IF_NOT_NULL	jump if step result isn't null
> 	EEOP_JUMP_IF_NOT_TRUE	jump if step result isn't TRUE
> 
> One could imagine later filling out this set with the other BoolTest
> condition types, but that seems to be all we need right now.

Hm, no arguments against, but I'm also not particularly excited about
the change.


> These are basically just renamings of the step types that exist now,
> although EEOP_ARRAYREF_CHECKINPUT would have to drop its not-very-
> necessary Assert(!op->d.arrayref.state->isassignment).

I won't shed a tear about that assert's removal.


> Well, I guess I should say that they're renamings of the semantics
> that I have for these steps in my working copy; for instance, I got
> rid of casewhen.value/casewhen.isnull in favor of letting CASE WHEN
> expressions evaluate into the CASE's final output variable.

That sounds like a sensible change (in the abstract, I obviously haven't
seen your working copy).


Greetings,

Andres Freund

Commits

  1. Improve performance of ExecEvalWholeRowVar.

  2. Remove unreachable code in expression evaluation.

  3. Faster expression evaluation and targetlist projection.

  4. Avoid syntax error on platforms that have neither LOCALE_T nor ICU.

  5. Add configure test to see if the C compiler has gcc-style computed gotos.

  6. Improve regression test coverage for TID scanning.

  7. Improve expression evaluation test coverage.

  8. Fix two errors with nested CASE/WHEN constructs.