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: pgsql-hackers@postgresql.org, Heikki Linnakangas <hlinnaka@iki.fi>, Tomas Vondra <tomas.vondra@2ndquadrant.com>
Date: 2017-03-15T19:58:38Z
Lists: pgsql-hackers 
On 2017-03-15 15:41:22 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > On March 15, 2017 12:33:28 PM PDT, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >> So for my money, you should drop 0002 altogether and just have 0004
> >> remove get_last_attnums() from execUtils.c and stick it into
> >> execExpr.c.  I suppose you still need the LastAttnumInfo API change
> >> so as to decouple it from ProjectionInfo, but that's minor.
> 
> > I think it's quite useful in other places too, we do repeated slot-getattrs in a bunch of places in the executor, and it's noticeable performance wise. 
> 
> Color me dubious.  Which specific other places have you got in mind, and
> do they have expression trees at hand that would tell them which columns
> they really need to pull out?

I was thinking of execGrouping.c's execTuplesMatch(),
TupleHashTableHash() (and unequal, but doubt that matters
performancewise).  There's also nodeHash.c's ExecHashGetValue(), but I
think that'd possibly better fixed differently.

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.