Re: Streaming Replication, can't select row in backup without specifying collation

On 7/25/22 15:36, Kelly Burkhart wrote:
> I have a primary and backup database running 12.10 and synced with
> streaming replication.  I have a simple table that is returning
> different results for the same query in the primary vs backup database.
>
> On the primary DB:
>
> > select tag::bytea, * from sentinel where tag =
> 'quote_merge_locs_mnj_NSX_20220719';
>                                  tag                                  |
>                tag                |           event_ts
> ----------------------------------------------------------------------+-----------------------------------+-------------------------------
>  \x71756f74655f6d657267655f6c6f63735f6d6e6a5f4e53585f3230323230373139 |
> quote_merge_locs_mnj_NSX_20220719 | 2022-07-19 20:29:14.114238-05
> (1 row)
>
> On the backup:
>
> > select tag::bytea, * from sentinel where tag =
> 'quote_merge_locs_mnj_NSX_20220719';
>  tag | tag | event_ts
> -----+-----+----------
> (0 rows)
>
> > select tag::bytea, * from sentinel where tag =
> 'quote_merge_locs_mnj_NSX_20220719' collate "C";
>                                  tag                                  |
>                tag                |           event_ts
> ----------------------------------------------------------------------+-----------------------------------+-------------------------------
>  \x71756f74655f6d657267655f6c6f63735f6d6e6a5f4e53585f3230323230373139 |
> quote_merge_locs_mnj_NSX_20220719 | 2022-07-19 20:29:14.114238-05
> (1 row)
>
> Can anyone explain why the backup does not show the row without
> specifying a collation?
>
> The primary is running CentOS 7.4, the backup is running CentOS 8.  The
> backup was created from a basebackup.  The postgres binaries were built
> on the OS on which they're running.  Neither were built with ICU (which
> I didn't know existed until tracking this down...).  Both databases show
> LC_COLLATE=en_US.UTF-8.
>
> The query "select * from pg_collation where collname like '%en_US%';"
> returns identical results for both databases.
>
> I'm concerned that somehow I've created a backup that is not compatible
> in some mysterious way with my primary.
>
> Can anyone provide any insight on what is going on?

See:

https://wiki.postgresql.org/wiki/Locale_data_changes

In particular:

https://wiki.postgresql.org/wiki/Locale_data_changes#RHEL.2FCentOS

>
> Thank you,
>
> -Kelly
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com