Horton

Re: Cutting initdb's runtime (Perl question embedded)

Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

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From: ilmari@ilmari.org (Dagfinn Ilmari Mannsåker )
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andreas Karlsson <andreas@proxel.se>, pgsql-hackers@postgreSQL.org, Andres Freund <andres@anarazel.de>
Date: 2017-04-17T16:49:54Z
Lists: pgsql-hackers

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Tom Lane <tgl@sss.pgh.pa.us> writes:

> There's certainly lots more that could be done in the genbki code,
> but I think all we can justify at this stage of the development
> cycle is to get the low-hanging fruit for testing speedups.

I threw Devel::NYTProf at it and picked some more low-hanging fruit.
Attached are separate patches for each change, and here are the runtimes
of genbki.pl and Gen_fmgrtab.pl, respectively, after each patch
(averages of 5 runs, in millseconds):

master (b6dd1271): 355, 182

1: Avoid unnecessary regex captures: 349, 183
2: Avoid repeated calls to SplitDataLine: 316, 158
3: Inline SplitDataLine: 291, 141
4: Inline check_natts: 287, 141

Together they shave 68ms or 19.2% off the runtime of genbki.pl and 41ms
or 22.5% off the runtime of Gen_fmgrtab.pl

Finally, one non-performance patch, which just removes the use of
Exporter in Catalog.pm, since none of the users actually import anything
from it.

- ilmari
-- 
"I use RMS as a guide in the same way that a boat captain would use
 a lighthouse.  It's good to know where it is, but you generally
 don't want to find yourself in the same spot." - Tollef Fog Heen

Commits

  1. Attempt to identify system timezone by reading /etc/localtime symlink.

  2. Make sure to run one initdb TAP test with no TZ set

  3. Use one transaction while reading postgres.bki, not one per line.

  4. Move bootstrap-time lookup of regproc OIDs into genbki.pl.