Re: Assertion failure in SnapBuildInitialSnapshot()

On Tue, Jan 31, 2023 at 3:56 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Jan 31, 2023 at 11:12 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Mon, Jan 30, 2023 at 9:41 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > I've attached patches for HEAD and backbranches. Please review them.
> >
>
> Shall we add a comment like the one below in
> ReplicationSlotsComputeRequiredXmin()?
> diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
> index f286918f69..e28d48bca7 100644
> --- a/src/backend/replication/slot.c
> +++ b/src/backend/replication/slot.c
> @@ -840,6 +840,13 @@ ReplicationSlotsComputeRequiredXmin(bool already_locked)
>
> Assert(ReplicationSlotCtl != NULL);
>
> + /*
> + * It is possible that by the time we compute the agg_xmin
> here and before
> + * updating replication_slot_xmin, the CreateInitDecodingContext() will
> + * compute and update replication_slot_xmin. So, we need to acquire
> + * ProcArrayLock here to avoid retreating the value of
> replication_slot_xmin.
> + */
> +

Agreed. It looks good to me.

Regards,

--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com