Horton

Re: row filtering for logical replication

Erik Rijkers <er@xs4all.nl>

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From: Erik Rijkers <er@xs4all.nl>
To: Euler Taveira <euler@timbira.com.br>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2018-03-01T21:25:02Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  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

Attachments

On 2018-03-01 16:27, Erik Rijkers wrote:
> 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.


Attached is 'logrep_rowfilter.sh', a demonstration of above-described 
bug.

The program runs initdb for 3 instances in /tmp (using ports 6515, 6516, 
and 6517) and sets up logical replication from 1->2->3.

It can be made to work by removing de where-clause on the second 'create 
publication' ( i.e., outcomment the $where2 variable ).


> Thanks,
> 
> 
> Erik Rijkers