Horton

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

Mark Dilger <mark.dilger@enterprisedb.com>

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From: Mark Dilger <mark.dilger@enterprisedb.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Dunstan <andrew@dunslane.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Joel Jacobson <joel@compiler.org>
Date: 2021-08-24T17:02:13Z
Lists: pgsql-hackers 

> On Aug 9, 2021, at 7:20 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 
> So I took another look at the code, and it doesn't seem that hard
> to make it act this way.  The attached passes regression, but
> I've not beat on it with random strings.
> alternate-fix-zero-quantified-nested-parens.patch

I've beaten on this with random patterns and it seems to hold up just fine.  I have also reviewed the diffs and, for the patterns where the output changes, everything looks correct.  I can't find anything wrong with this patch.

—
Mark Dilger
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.