Horton

Re: Another regexp performance improvement: skip useless paren-captures

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

View thread View on postgr.es
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Joel Jacobson <joel@compiler.org>
Date: 2021-08-10T00:57:31Z
Lists: pgsql-hackers 
Mark Dilger <mark.dilger@enterprisedb.com> writes:
>> On Aug 9, 2021, at 12:14 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Pushed, but while re-reading it before commit I noticed that there's
>> some more fairly low-hanging fruit in regexp_replace().

> I've been reviewing and testing this (let-regexp_replace-use-NOSUB.patch) since you sent it 4 hours ago, and I can't seem to break it.  There are pre-existing problems in the regex code, but this doesn't seem to add any new breakage.

Pushed that bit, thanks for testing!

I plan to not do anything about the (()){0} bug until after the release
window, since that will need to be back-patched.  That bug's gotta be
twenty years old, so while I kinda wish we'd found it a few days
earlier, waiting another 3 months won't make much difference.

			regards, tom lane

Commits

  1. Fix regexp misbehavior with capturing parens inside "{0}".

  2. Let regexp_replace() make use of REG_NOSUB when feasible.

  3. Fix bogus assertion in BootstrapModeMain().

  4. Avoid determining regexp subexpression matches, when possible.

  5. Check the size in COPY_POINTER_FIELD

  6. Make regexp engine's backref-related compilation state more bulletproof.