Re: row filtering for logical replication - Mailing list pgsql-hackers

From Amit Kapila
Subject Re: row filtering for logical replication
Date
Msg-id CAA4eK1+hVXfOSScbf5LUB=5is=wYaC6NBhLxuvetbWQnZRnsVQ@mail.gmail.com
Whole thread Raw
In response to Re: row filtering for logical replication  ("Euler Taveira" <euler@eulerto.com>)
Responses Re: row filtering for logical replication
Re: row filtering for logical replication
List pgsql-hackers
On Mon, Nov 29, 2021 at 8:40 PM Euler Taveira <euler@eulerto.com> wrote:
>
> On Mon, Nov 29, 2021, at 7:11 AM, Amit Kapila wrote:
>
> I don't think it is a good idea to combine the row-filter from the
> publication that publishes just 'insert' with the row-filter that
> publishes 'updates'. We shouldn't apply the 'insert' filter for
> 'update' and similarly for publication operations. We can combine the
> filters when the published operations are the same. So, this means
> that we might need to cache multiple row-filters but I think that is
> better than having another restriction that publish operation 'insert'
> should also honor RI columns restriction.
>
> That's exactly what I meant to say but apparently I didn't explain in details.
> If a subscriber has multiple publications and a table is part of these
> publications with different row filters, it should check the publication action
> *before* including it in the row filter list. It means that an UPDATE operation
> cannot apply a row filter that is part of a publication that has only INSERT as
> an action. Having said that we cannot always combine multiple row filter
> expressions into one. Instead, it should cache individual row filter expression
> and apply the OR during the row filter execution (as I did in the initial
> patches before this caching stuff). The other idea is to have multiple caches
> for each action.  The main disadvantage of this approach is to create 4x
> entries.
>
> I'm experimenting the first approach that stores multiple row filters and its
> publication action right now.
>

We can try that way but I think we should still be able to combine in
many cases like where all the operations are specified for
publications having the table or maybe pubactions are same. So, we
should not give up on those cases. We can do this new logic only when
we find that pubactions are different and probably store them as
independent expressions and corresponding pubactions for it at the
current location in the v42* patch (in pgoutput_row_filter). It is
okay to combine them at a later stage during execution when we can't
do it at the time of forming cache entry.

-- 
With Regards,
Amit Kapila.



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