Date: Thu, 1 Mar 2018 17:06:42 +0100
From: David Fetter <david@fetter.org>
To: Euler Taveira <euler@timbira.com.br>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: row filtering for logical replication
Message-ID: <20180301160642.GH25493@fetter.org>
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On Thu, Mar 01, 2018 at 12:41:04PM -0300, Euler Taveira wrote:
> 2018-02-28 21:47 GMT-03:00 David Fetter <david@fetter.org>:
> > I noticed that the WHERE clause applies to all tables in the
> > publication.  Is that actually the right thing?  I'm thinking of a
> > case where we have foo(id, ...) and bar(foo_id, ....).  To slice that
> > correctly, we'd want to do the ids in the foo table and the foo_ids in
> > the bar table.  In the system as written, that would entail, at least
> > potentially, writing a lot of publications by hand.
> >
> I didn't make it clear in my previous email and I think you misread
> the attached docs. Each table can have an optional WHERE clause. I'll
> made it clear when I rewrite the tests. Something like:

Sorry I misunderstood.

> CREATE PUBLICATION tap_pub FOR TABLE tab_rowfilter_1 WHERE (a > 1000
> AND b <> 'filtered'), tab_rowfilter_2 WHERE (c % 2 = 0),
> tab_rowfilter_3;

That's great!

> Such syntax will not block another future feature that will publish
> only few columns of the table.
> 
> > I also noticed that in psql, \dRp+ doesn't show the WHERE clause,
> > which it probably should.
> >
> Yea, it could be added be I'm afraid of such long WHERE clauses.

I think of + as signifying, "I am ready to get a LOT of output in
order to see more detail."  Perhaps that's just me.

> > Does it need regression tests?
> >
> I included some tests just to demonstrate the feature but I'm
> planning to add a separate test file for it.

Excellent. This feature looks like a nice big chunk of the user-space
infrastructure needed for sharding, among other things.

Best,
David.
-- 
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778

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