Horton

Re: row filtering for logical replication

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Peter Smith <smithpb2250@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Ajin Cherian <itsajin@gmail.com>, Greg Nancarrow <gregn4422@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Euler Taveira <euler@eulerto.com>, Rahila Syed <rahilasyed90@gmail.com>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Önder Kalacı <onderkalaci@gmail.com>, japin <japinli@hotmail.com>, Michael Paquier <michael@paquier.xyz>, David Steele <david@pgmasters.net>, Craig Ringer <craig@2ndquadrant.com>, Amit Langote <amitlangote09@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2021-11-18T12:46:43Z
Lists: pgsql-hackers

Commits

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  1. Release cache tuple when no longer needed

  2. Add some additional tests for row filters in logical replication.

  3. Fix one of the tests introduced in commit 52e4f0cd47.

  4. Allow specifying row filters for logical replication of tables.

  5. Move scanint8() to numutils.c

  6. Replace Test::More plans with done_testing

  7. Reduce relcache access in WAL sender streaming logical changes

  8. Small cleanups related to PUBLICATION framework code

  9. Add a view to show the stats of subscription workers.

  10. Allow publishing the tables of schema.

  11. Doc: improve documentation of CREATE/ALTER SUBSCRIPTION.

  12. Add PublicationTable and PublicationRelInfo structs

  13. Remove unused argument "txn" in maybe_send_schema().

  14. Add prepare API support for streaming transactions in logical replication.

  15. Unify PostgresNode's new() and get_new_node() methods

  16. Use l*_node() family of functions where appropriate

  17. Add support for prepared transactions to built-in logical replication.

  18. Restore the portal-level snapshot after procedure COMMIT/ROLLBACK.

  19. Rename a parse node to be more general

  20. Remove unused column atttypmod from initial tablesync query

  21. SEARCH and CYCLE clauses

On Thu, Nov 18, 2021 at 11:02 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> On Mon, Nov 15, 2021 at 9:31 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> >
> > 5. Why do you need a separate variable rowfilter_valid to indicate
> > whether a valid row filter exists? Why exprstate is not sufficient?
> > Can you update comments to indicate why we need this variable
> > separately?
>
> I have improved the (existing) comment in v40 [1].
>
> >
> > 0004*
> > 6. In rowfilter_expr_checker(), the expression tree is traversed
> > twice, can't we traverse it once to detect all non-allowed stuff? It
> > can be sometimes costly to traverse the tree multiple times especially
> > when the expression is complex and it doesn't seem acceptable to do so
> > unless there is some genuine reason for the same.
>
> I kind of doubt there would be any perceptible difference for 2
> traverses instead of 1 because:
> a) filters are limited to simple expressions. Yes, a large boolean
> expression is possible but I don't think it is likely.
>

But in such cases, it will be quite costly and more importantly, I
don't see any good reason why we need to traverse it twice..

> b) the validation part is mostly a one-time execution only when the
> filter is created or changed.
>
> Anyway, I am happy to try to refactor the logic to a single traversal
> as suggested, but I'd like to combine those "validation" patches
> (v40-0005, v40-0006) first, so I can combine their walker logic. Is it
> OK?
>

That should be okay. You can combine the logic of v40-0005 and
v40-0006, and then change it so that you need to traverse the
expression once.

-- 
With Regards,
Amit Kapila.