Re: row filtering for logical replication

On Thu, Nov 18, 2021 at 11:02 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>
> On Mon, Nov 15, 2021 at 9:31 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> >
> > 4. I think we should add some comments in pgoutput_row_filter() as to
> > why we are caching the row_filter here instead of
> > get_rel_sync_entry()? That has been discussed multiple times so it is
> > better to capture that in comments.
>
> Added comment in v40 [1]
>

I think apart from truncate and error cases, it can also happen for
other operations because we decide whether to publish a change
(operation) after calling get_rel_sync_entry() in pgoutput_change. I
think we can reflect that as well in the comment.

> >
> > 5. Why do you need a separate variable rowfilter_valid to indicate
> > whether a valid row filter exists? Why exprstate is not sufficient?
> > Can you update comments to indicate why we need this variable
> > separately?
>
> I have improved the (existing) comment in v40 [1].
>

One more thing related to this code:
pgoutput_row_filter()
{
..
+ if (!entry->rowfilter_valid)
{
..
+ oldctx = MemoryContextSwitchTo(CacheMemoryContext);
+ tupdesc = CreateTupleDescCopy(tupdesc);
+ entry->scantuple = MakeSingleTupleTableSlot(tupdesc, &TTSOpsHeapTuple);
+ MemoryContextSwitchTo(oldctx);
..
}

Why do we need to initialize scantuple here unless we are sure that
the row filter is going to get associated with this relentry? I think
when there is no row filter then this allocation is not required.

--
With Regards,
Amit Kapila.