Re: replication consistency checking

On Fri, Jun 5, 2015 at 4:40 AM, Sergey Konoplev <gray(dot)ru(at)gmail(dot)com> wrote:

> On Wed, Jun 3, 2015 at 9:49 PM, hydra <hydrapolic(at)gmail(dot)com> wrote:
> > After setting up streaming replication, is it possible to check whether
> the
> > slave has the same data as the master?
> >
> > In the MySQL world there is the percona-toolkit with pt-table-checksum
> that
> > does this job:
> > https://www.percona.com/doc/percona-toolkit/2.2/pt-table-checksum.html
>
> I believe you only need
>
> http://www.postgresql.org/docs/9.4/static/app-initdb.html#APP-INITDB-DATA-CHECKSUMS
> .
>
> --
> Kind regards,
> Sergey Konoplev
> PostgreSQL Consultant and DBA
>
> http://www.linkedin.com/in/grayhemp
> +1 (415) 867-9984, +7 (499) 346-7196, +7 (988) 888-1979
> gray(dot)ru(at)gmail(dot)com
>

Thank you all for replies,
while looking for replication information I found this:
http://thebuild.com/presentations/worst-day-fosdem-2014.pdf

It's a real life experience of hitting this replication bug:
https://wiki.postgresql.org/wiki/Nov2013ReplicationIssue

The primary symptom of this corruption is rows that:

- are present on the master, but missing on the replica
- have been deleted on the master still appear to be visible on the
replica
- have been updated, and their old versions appear alongside the new,
updated versions on the replica

How can I verify whether I already have this corruption?
There is no known way to identify that the issue has affected a standby in
the past but comparing the data from the primary with the standby.

So hands up who still think PostgreSQL doesn't need some way of checking
the data consistency between master-standby? :)