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Re: SIMILAR TO expressions translate wildcards where they shouldn't

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-bugs@lists.postgresql.org
Date: 2025-05-27T05:57:45Z
Lists: pgsql-bugs

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On Fri, May 23, 2025 at 11:42:10AM +0200, Laurenz Albe wrote:
> I also improved the code by adding more comments.
> I renamed "incharclass" to "charclass_depth", which is more descriptive.
> 
> Also, I had to work some more on handling carets:
> While the closing bracket is a regular character in []] and [^]], it
> is not in expressions like [^^].

The transformation with the patch:
'^(?:\.[.[:alnum:]_].[]%].*[^]$]\$[^^]\^[(](?:p))$'
And on HEAD:
'^(?:\.[.[:alnum:].].[].*].*[^]\$]\$[^^]\^[(](?:p))$'

If I am not missing something, '%', '_', '$', single and double carets
at the beginning are covered.  '.' and '(' are not.

Anyway, that's really hard to parse so I would suggest to split each
check into queries of their own to show individual conversions in
these EXPLAIN outputs (we don't care if tese regexps are correct, just
want to check the output to the POSIX style).  I am OK with the point
based on charclass_start to count the number of carets at the
beginning of a character class.

With some tweaks and the tests reworked, I am finishing with the
reviewed version attached.  What do you think?
--
Michael

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Adjust regex for test with opening parenthesis in character classes

  2. Fix conversion of SIMILAR TO regexes for character classes