| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Cc: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Greg Nancarrow <gregn4422(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Euler Taveira <euler(at)eulerto(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Önder Kalacı <onderkalaci(at)gmail(dot)com>, japin <japinli(at)hotmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, David Steele <david(at)pgmasters(dot)net>, Craig Ringer <craig(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Amit Langote <amitlangote09(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: row filtering for logical replication |
| Date: | 2021-07-20 09:00:07 |
| Message-ID: | CAA4eK1+AXEd5bO-qPp6L9Ptckk09nbWvP8V7q5UW4hg+kHjXwQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jul 20, 2021 at 9:54 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Mon, Jul 19, 2021 at 4:31 PM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >
> > On Mon, Jul 19, 2021 at 3:12 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >
> > > > Maybe a second option is to have replication change any UPDATE into
> > > > either an INSERT or a DELETE, if the old or the new row do not pass the
> > > > filter, respectively. That way, the databases would remain consistent.
> >
> > Yeah, I think this is the best way to keep the data consistent.
> >
>
> Today, while studying the behavior of this particular operation in
> other databases, I found that IBM's InfoSphere Data Replication does
> exactly this. See [1]. I think there is a merit if want to follow this
> idea.
>
As per my initial analysis, there shouldn't be much difficulty in
implementing this behavior. We need to change the filter API
(pgoutput_row_filter) such that it tells us whether the filter is
satisfied by the old row, new row or both and then the caller should
be able to make a decision based on that. I think that should be
sufficient to turn update to insert/delete when required. I might be
missing something here but this doesn't appear to require any drastic
changes in the patch.
--
With Regards,
Amit Kapila.
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