Re: Weird behavior with unique constraint not respected, and random results on same queries

Hi Magnus,

thank you for you quick and relevant answer, you saved my day !

Le 12/10/2020 à 17:53, Magnus Hagander a écrit :
>
>
> On Mon, Oct 12, 2020 at 5:43 PM Thomas SIMON <tsimon(at)neteven(dot)com
> <mailto:tsimon(at)neteven(dot)com>> wrote:
>
> Hi all,
>
> I encounter strange behavior since a few days, and the promote of a
> recently installed server as master in my infrastructure (debian
> 10, was
> added as slave a few days ago)
> I use postgresql 12.4 on master an slave.
>
>
> Is the previous master also Debian 10?
Yes old master was debian 9
>
> Specifically, when upgrading to Debian 10 you need to reindex all
> indexes on text fields (see
> https://wiki.postgresql.org/wiki/Locale_data_changes
> <https://wiki.postgresql.org/wiki/Locale_data_changes>). This can in
> particular cause problems in replication, whereby your primary and
> standby nodes have to run the same version of Debian since you cannot
> do a separate reindex on the standby.
>
> E.g. if your master is Debian 9, then you can expect some lookups to
> be incorrect on the standby, and after you do a failover you may see
> entries with invalid values in a unique index go in because of the
> lack of reindex.
I haven't found this note before, ans it seems indeed to describe the
exact problem that we have...
I just upgraded old master to avoid these kind of problems.
>
>
> Since the promote, I find on database some duplicated entries ,
> despite
> the fact that the constraint should not allow this.
> It seems to only happens with entries having "special" characters
> (understand " ", "-", "+", ...)
>
>
> As you can see from the locale page above, the changes are
> specifically around special characters, so this is an indication that
> it might be this problem.
Exactly yes
>
> If this is the problem, the fix is a REINDEX and to make sure that all
> nodes in the replication cluster use the same version of the
> collections in the future. If the reindex fails because of existing
> duplicate entries, you will have to find a way to clean those up
> before reindexing. You may have to drop the indexes, then clean up,
> and then recreate them.

Yes, we are working on a script which will delete all duplicate values,
and then we will use reindex with concurrently option on all listed lindexs

We'll do these actions tomorrow morning, and I'll keep you updated about
the result.

>
> --
>  Magnus Hagander
>  Me: https://www.hagander.net/ <http://www.hagander.net/>
>  Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>