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Date: Thu, 01 Mar 2018 16:27:11 +0100
From: Erik Rijkers <er@xs4all.nl>
To: Euler Taveira <euler@timbira.com.br>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: row filtering for logical replication
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On 2018-03-01 00:03, Euler Taveira wrote:
> The attached patches add support for filtering rows in the publisher.

> 001-Refactor-function-create_estate_for_relation.patch
> 0002-Rename-a-WHERE-node.patch
> 0003-Row-filtering-for-logical-replication.patch

> Comments?

Very, very useful.  I really do hope this patch survives the 
late-arrival-cull.

I built this functionality into a test program I have been using and in 
simple cascading replication tests it works well.

I did find what I think is a bug (a bug easy to avoid but also easy to 
run into):
The test I used was to cascade 3 instances (all on one machine) from 
A->B->C
I ran a pgbench session in instance A, and used:
   in A: alter publication pub0_6515 add table pgbench_accounts where 
(aid between 40000 and 60000-1);
   in B: alter publication pub1_6516 add table pgbench_accounts;

The above worked well, but when I did the same but used the filter in 
both publications:
   in A: alter publication pub0_6515 add table pgbench_accounts where 
(aid between 40000 and 60000-1);
   in B: alter publication pub1_6516 add table pgbench_accounts where 
(aid between 40000 and 60000-1);

then the replication only worked for (pgbench-)scale 1 (hence: very 
little data); with larger scales it became slow (taking many minutes 
where the above had taken less than 1 minute), and ended up using far 
too much memory (or blowing up/crashing altogether).  Something not 
quite right there.

Nevertheless, I am much in favour of acquiring this functionality as 
soon as possible.


Thanks,


Erik Rijkers