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

Laurenz Albe <laurenz.albe@cybertec.at>

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From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Michael Paquier <michael@paquier.xyz>
Cc: pgsql-bugs@lists.postgresql.org
Date: 2025-05-23T09:42:10Z
Lists: pgsql-bugs

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On Fri, 2025-05-23 at 12:22 +0900, Michael Paquier wrote:
> Anyway, I don't think that the tests in the patch are complete.  For
> example, '[[^](]' is transformed into '^(?:[[^](])$' in the SIMILAR TO
> conversion with the patch, and before the patch we get
> '^(?:[[^](?:])$'.  Note the translation of the last parenthesis '(' to
> "(?:" when inside the character class, but your patch does not
> document that.  AFAIU, we should not convert the parenthesis '(' while
> in a multi-level character class as the patch does, but we have no
> tests for it and the patch does not document this part, either.
> 
> Could it be possible to split the single SIMILAR TO expression into
> multiple smaller pieces for each character that should not be
> converted while inside a character class?  This is hard to parse as
> written in your proposal of patch.

I have changed the regression test like you suggest.

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 [^^].

Yours,
Laurenz Albe

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