Re: [PATCH] Provide more information to filter_prepare

On Wed, Mar 10, 2021 at 4:26 PM Markus Wanner
<markus(dot)wanner(at)enterprisedb(dot)com> wrote:
>
> On 10.03.21 11:18, Amit Kapila wrote:
> > On Tue, Mar 9, 2021 at 2:14 PM Markus Wanner
> > <markus(dot)wanner(at)enterprisedb(dot)com> wrote:
> >> currently, only the gid is passed on to the filter_prepare callback.
> >> While we probably should not pass a full ReorderBufferTXN (as we do for
> >> most other output plugin callbacks), a bit more information would be
> >> nice, I think.
> >
> > How the proposed 'xid' parameter can be useful? What exactly plugins
> > want to do with it?
>
> The xid is the very basic identifier for transactions in Postgres. Any
> output plugin that interacts with Postgres in any way slightly more
> interesting than "filter by gid prefix" is very likely to come across a
> TransactionId.
>
> It allows for basics like checking if the transaction to decode still is
> in progress, for example.
>

But this happens when we are decoding prepare, so it is clear that the
transaction is prepared, why any additional check?

> Or in a much more complex scenario, decide on
> whether or not to filter based on properties the extension stored during
> processing the transaction.
>

What in this can't be done with GID and how XID can achieve it?

--
With Regards,
Amit Kapila.