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: Ants Aasma <ants.aasma@eesti.ee>, Heikki Linnakangas <hlinnaka@iki.fi>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2017-03-27T15:17:50Z
Lists: pgsql-hackers 
On 2017-03-27 09:33:43 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > Checking for this isn't entirely pretty - see my attached attempt at
> > doing so.  I considered hiding
> > __attribute__((optimize("no-crossjumping"))) in execInterpExpr.c behind
> > a macro (like PG_DISABLE_CROSSJUMPING), but I don't really think that
> > makes things better.
> 
> I think it would, primarily because if we find out that some other compiler
> spells this differently, we could handle it totally within configure.

I'm unconvinced that we could sensibly map different compiler's options
on the same option name - I'd be surprised if they would have a similar
enough effect.


> Isn't our practice to put __attribute__ at the end of a function
> declaration or definition, not in the middle someplace?

We could move it to the declaration - which doesn't seem like an
improvement here, given that it's about optimization not API changes -
but in definitions you can't move it after the function name:
static Datum
ExecInterpExpr(ExprState *state, ExprContext *econtext, bool *isnull)
#ifdef HAVE_FUNCATTR_NO_CROSSJUMPING
__attribute__((optimize("no-crossjumping")))
#endif
:
/home/andres/src/postgresql/src/backend/executor/execExprInterp.c:279:1: error: attributes should be specified before the declarator in a function definition


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.