Re: String comparison fails for some cases after migration

Hi,

On Wed, Oct 27, 2021 at 2:12 PM Jayadevan M <maymala(dot)jayadevan(at)gmail(dot)com> wrote:
>
> We moved our PostgreSQL database from one hosting provider to another using pgbackrest. In the new environment, some comparison operations were failing. The issue was fixed by running an update. But I am trying to find out what would have happened.
>
> select * from accounts where email = 'someemail(at)gmail(dot)com'; -- failed for some email ids even though there were records.
>
> select * from accounts where lower(trim(email)) <> email; -- fetched no records.
>
> select * from accounts where email::bytea = 'someemail(at)gmail(dot)com'::bytea; - worked for those records where comparison was failing.
>
> update accounts set email = trim(lower(email)); -- fixed the issue.
>
> Source database was PG 13.2, target 13.3.
>
> Any suggestions will be appreciated - not sure if other tables/columns are affected.

Most likely you had a different version of the glibc or ICU libraries
on the new system, which lead to your indexes on collatable datatypes
partially corrupted. See https://wiki.postgresql.org/wiki/Collations
for more details.

You can issue a REINDEX for each impacted index, or a database-wide REINDEX.