Re: Column Filtering in Logical Replication

From: Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>
To: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Cc: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, "houzj(dot)fnst(at)fujitsu(dot)com" <houzj(dot)fnst(at)fujitsu(dot)com>, Rahila Syed <rahilasyed90(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, shiy(dot)fnst(at)fujitsu(dot)com
Subject: Re: Column Filtering in Logical Replication
Date: 2022-03-09 09:20:57
Message-ID: a5e04445-85a0-ef43-5a02-996ae59f301d@enterprisedb.com
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On 07.03.22 16:18, Tomas Vondra wrote:
> AFAICS these issues should be resolved by the adoption of the row-filter
> approach (i.e. it should fail the same way as for row filter).

The first two patches (additional testing for row filtering feature)
look okay to me.

Attached is a fixup patch for your main feature patch (the third one).

It's a bit of code and documentation cleanup, but mainly I removed the
term "column filter" from the patch. Half the code was using "column
list" or similar and half the code "column filter", which was confusing.
Also, there seemed to be a bit of copy-and-pasting from row-filter
code going on, with some code comments not quite sensible, so I rewrote
some of them. Also some code used "rf" and "cf" symbols which were a
bit hard to tell apart. A few more letters can increase readability.

Note in publicationcmds.c OpenTableList() the wrong if condition was used.

I'm still confused about the intended replica identity handling. This
patch still checks whether the column list contains the replica identity
at DDL time. And then it also checks at execution time. I thought the
latest understanding was that the DDL-time checking would be removed. I
think it's basically useless now, since as the test cases show, you can
subvert those checks by altering the replica identity later.

Attachment Content-Type Size
0001-fixup-Allow-specifying-column-filters-for-logical-re.patch text/plain 71.8 KB

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