| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Joel Jacobson <joel(at)compiler(dot)org> |
| Subject: | Re: Another regexp performance improvement: skip useless paren-captures |
| Date: | 2021-08-08 20:25:00 |
| Message-ID: | 3224306.1628454300@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> writes:
> Hmm. This changes the behavior when applied against master (c1132aae336c41cf9d316222e525d8d593c2b5d2):
> select regexp_split_to_array('uuuzkodphfbfbfb', '((.))(\1\2)', 'ntw');
> regexp_split_to_array
> -----------------------
> - {"",zkodphfbfbfb}
> + {uuuzkodphfbfbfb}
> (1 row)
Ugh. The regex engine is finding the match correctly, but it's failing to
tell the caller where it is :-(. I was a little too cute in optimizing
the regmatch_t result-vector copying in pg_regexec, and forgot to ensure
that the overall match position would be reported.
Thanks for the testing!
regards, tom lane
| Attachment | Content-Type | Size |
|---|---|---|
| optimize-useless-captures-3.patch | text/x-diff | 14.6 KB |
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