Horton

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

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

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Andrew Dunstan <andrew@dunslane.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Joel Jacobson <joel@compiler.org>
Date: 2021-08-05T15:01:29Z
Lists: pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> Well, I consider myself a pretty fair perl programmer, and I know
> there's a way to do that, but I never do it, and I would have had to
> look up the exact syntax. So +1 from me for anything automatic that
> avoids paying the overhead in some cases.

That's my feeling about it too --- I never really think of this
point when writing a regexp.  It seems like something the engine
ought to handle gracefully, so this patch is an attempt to do so.

			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.