Horton

Re: WIP: Faster Expression Processing and Tuple Deforming (including JIT)

Nico Williams <nico@cryptonector.com>

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From: Nico Williams <nico@cryptonector.com>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org, Heikki Linnakangas <hlinnaka@iki.fi>, Doug Doole <ddoole@salesforce.com>
Date: 2016-12-06T21:22:54Z
Lists: pgsql-hackers 
On Tue, Dec 06, 2016 at 12:36:41PM -0800, Andres Freund wrote:
> On 2016-12-06 15:25:44 -0500, Tom Lane wrote:
> > I'm not entirely thrilled with the idea of this being a configure-time
> > decision, because that forces packagers to decide for their entire
> > audience whether it's okay to depend on LLVM.  That would be an untenable
> > position to put e.g. Red Hat's packagers in: either they screw the people
> > who want performance or they screw the people who want security.

There's no security issue.  The dependency is on LLVM libraries, not
LLVM front-ends (e.g., clang(1)).

I don't think there's a real issue as to distros/packagers/OS vendors.
They already have to package LLVM, and they already package LLVM
libraries separately from LLVM front-ends.

> The argument for not install a c compiler seems to be that it makes it
> less convenient to build an executable. I doubt that having a C(++)
> library for code generation is convenient enough to change the picture
> there.

The security argument goes back to the days of the Morris worm, which
depended on having developer tools (specifically in that case, ld(1),
the link-editor).  But JIT via LLVM won't give hackers a way to generate
or link arbitrary object code.

Nico
--

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.