Re: [PATCH] Use indexes on the subscriber when REPLICA IDENTITY is full on the publisher

Hi,

On 2023-03-01 14:10:07 +0530, Amit Kapila wrote:
> On Wed, Mar 1, 2023 at 12:09 AM Andres Freund <andres@anarazel.de> wrote:
> >
> > > I see this as a way to provide this feature for users but I would
> > > prefer to proceed with this if we can get some more buy-in from senior
> > > community members (at least one more committer) and some user(s) if
> > > possible. So, I once again request others to chime in and share their
> > > opinion.
> >
> > I'd prefer not having an option, because we figure out the cause of the
> > performance regression (reducing it to be small enough to not care). After
> > that an option defaulting to using indexes.
> >
> 
> Sure, if we can reduce regression to be small enough then we don't
> need to keep the default as false, otherwise, also, we can consider it
> to keep an option defaulting to using indexes depending on the
> investigation for regression. Anyway, the main concern was whether it
> is okay to have an option for this which I think we have an agreement
> on, now I will continue my review.

I think even as-is it's reasonable to just use it. The sequential scan
approach is O(N^2), which, uh, is not good. And having an index over thousands
of non-differing values will generally perform badly, not just in this
context.

Greetings,

Andres Freund