Thread

1. BUG #18870: weird behavior with regexp_replace

   PG Bug reporting form <noreply@postgresql.org> — 2025-03-27T13:43:50Z

   The following bug has been logged on the website:
   
   Bug reference:      18870
   Logged by:          reinko
   Email address:      devops@key2asset.com
   PostgreSQL version: 17.4
   Operating system:   Ubuntu 11.4.0-1ubuntu1~22.04
   Description:        
   
   select regexp_replace(LOWER('Örebro'), '\W', '_', 'g')  in postgres 15 the
   result is örebro which is correct since ö should fit in the \w for a
   regex.
   select regexp_replace(LOWER('Örebro'), '\W', '_', 'g') --> since postgres 17
   the result is _rebro which is incorrect since \w should also contain
   characters like ö, ä, ë.
   
   the to lower is not really relevant to this issue the same happens when it's
   just a direct string aswell.
   this issue happens with alot of special a-z characters é, è have the same
   issue for example.
   
   Kind regards,
   Reinko Brink
   
   

2. Re: BUG #18870: weird behavior with regexp_replace

   Tom Lane <tgl@sss.pgh.pa.us> — 2025-03-27T21:23:58Z

   PG Bug reporting form <noreply@postgresql.org> writes:
   > select regexp_replace(LOWER('Örebro'), '\W', '_', 'g')  in postgres 15 the
   > result is örebro which is correct since ö should fit in the \w for a
   > regex.
   > select regexp_replace(LOWER('Örebro'), '\W', '_', 'g') --> since postgres 17
   > the result is _rebro which is incorrect since \w should also contain
   > characters like ö, ä, ë.
   
   This most likely indicates that you've got a different database
   collation selected in the v17 installation.  Postgres defers to
   the LC_CTYPE setting (or, in some configurations, the ICU collation)
   to decide what is a letter.  See
   
   https://www.postgresql.org/docs/current/charset.html
   
   psql's "\l" command will give a quick overview of what collations
   you have selected.
   
   			regards, tom lane