Horton

Re: BUG #19406: substring(text) fails on valid UTF-8 toasted value in PostgreSQL 15.16

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: ranvis@gmail.com, pgsql-bugs@lists.postgresql.org
Cc: thomas.munro@gmail.com
Date: 2026-02-17T18:15:18Z
Lists: pgsql-bugs

Attachments

On Fri, Feb 13, 2026 at 04:21:13PM -0800, Noah Misch wrote:
> On Fri, Feb 13, 2026 at 02:48:04PM -0800, Noah Misch wrote:
> > Attached.  I may add some more tests, e.g. a toasted invalid string where the
> > detoasted length is less than the slice we request.
> 
> Tests already covered that in particular, but I added some other tests.

I cast a wider net for string function bugs specific to toasted strings and/or
multibyte text.  That yielded the attached.  This did reproduce $SUBJECT, but
it didn't find additional bugs.  The method is crude, but I'm archiving it
here so folks know the testing happened and in case someone pursues similar
testing in the future.

Commits

  1. Suppress new "may be used uninitialized" warning.

  2. Fix SUBSTRING() for toasted multibyte characters.

  3. pg_mblen_range, pg_mblen_with_len: Valgrind after encoding ereport.