Re: pg_checksums?

On 2023-10-29 10:11:07 +0100, Paul Förster wrote:
> On Oct 29, 2023, at 02:43, Peter J. Holzer <hjp-pgsql(at)hjp(dot)at> wrote:
> > I don't think so. AFAIK Replication keeps the data files in sync on a
> > bit-for-bit level and turning on checksums changes the data layout.
> > Running a cluster where one node has checksums and the other doesn't
> > would result in a complete mess.
>
> I agree with the last sentence. This is why I asked if it is safe to
> enable checksums on a replica, switch over and then do it again on the
> ex primary, i.e. now new replica without doing a reinit.

It *might* work if there are zero writes on the primary during the
downtime of the replica (because those writes couldn't be replicated),
but that seems hard to ensure. Even if you could get away with making
the primary read-only (is this even possible?) I wouldn't have much
confidence in the result and reinit the (new) replica anyway.

hp

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