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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>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Joel Jacobson <joel@compiler.org>
Subject: Re: Another regexp performance improvement: skip useless paren-captures
Date: Tue, 24 Aug 2021 10:02:13 -0700
Message-ID: <51ED454F-0F52-4D66-8117-1DB0363240DF@enterprisedb.com> (raw)
In-Reply-To: <3756810.1628562033@sss.pgh.pa.us>
References: <2219936.1628115334@sss.pgh.pa.us>
	<31908a04-f73b-8c5b-ed99-919fd4cd4b54@dunslane.net>
	<2390507.1628174181@sss.pgh.pa.us>
	<2BFE7DFD-8537-4B4E-BC4C-2F265A836651@enterprisedb.com>
	<3173384.1628442278@sss.pgh.pa.us>
	<BDB634FD-2EE5-4697-91A0-1F53E1363D3B@enterprisedb.com>
	<3224306.1628454300@sss.pgh.pa.us>
	<D6AF940F-C48A-4666-A6E0-B92FC96F0711@enterprisedb.com>
	<3289730.1628461693@sss.pgh.pa.us>
	<B323249F-B221-4DCE-8763-E5070A77452E@enterprisedb.com>
	<3534632.1628536485@sss.pgh.pa.us>
	<A099E4A8-4377-4C64-A98C-3DEDDC075502@enterprisedb.com>
	<3643732.1628551901@sss.pgh.pa.us>
	<1303A200-4615-4559-961A-CC906DE07EAF@enterprisedb.com>
	<3756810.1628562033@sss.pgh.pa.us>



> 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








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