Horton

Re: Minimal logical decoding on standbys

Fabrízio de Royes Mello <fabriziomello@gmail.com>

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From: Fabrízio de Royes Mello <fabriziomello@gmail.com>
To: "Drouvot, Bertrand" <bdrouvot@amazon.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>, Andres Freund <andres@anarazel.de>, tushar <tushar.ahuja@enterprisedb.com>, "[pgdg] Robert Haas" <robertmhaas@gmail.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, Rahila Syed <rahila.syed@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2021-03-23T13:18:04Z
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. Reduce the log level in 035_standby_logical_decoding.pl.

  2. 035_standby_logical_decoding: Add missing waits for replication

  3. For cascading replication, wake physical and logical walsenders separately

  4. Handle logical slot conflicts on standby

  5. Support invalidating replication slots due to horizon and wal_level

  6. Prevent use of invalidated logical slot in CreateDecodingContext()

  7. Replace replication slot's invalidated_at LSN with an enum

  8. Pass down table relation into more index relation functions

  9. Assert only valid flag bits are passed to visibilitymap_set()

  10. Remove unused _bt_delitems_delete() argument.

  11. Add xl_btree_delete optimization.

On Tue, Mar 23, 2021 at 8:47 AM Drouvot, Bertrand <bdrouvot@amazon.com>
wrote:
>
> I have one remark regarding the conflicts:
>
> The logical slots are dropped if a conflict is detected.
>
> But, if the slot is not active before being dropped (say wal_level is
changed to  < logical on master and a logical slot is not active on the
standby) then its corresponding
pg_stat_database_conflicts.confl_logicalslot is not incremented (as it
would be incremented "only" during the cancel of an "active" backend).
>
> I think, it should be incremented in all the cases (active or not), what
do you think?
>

Good catch... IMHO it should be incremented as well!!!

> I updated the patch to handle this scenario (see the new
pgstat_send_droplogicalslot() in
v12-0003-Handle-logical-slot-conflicts-on-standby.patch).
>

Perfect.

> I also added more tests in 023_standby_logical_decoding_conflicts.pl to
verify that pg_stat_database_conflicts.confl_logicalslot is updated as
expected (see check_confl_logicalslot() in
v12-0004-New-TAP-test-for-logical-decoding-on-standby.patch).
>

Perfect.

> Except this remark and the associated changes, then it looks good to me.
>

LGTM too... Reviewing new changes now to move it forward and make this
patch set ready for commiter review.

Regards,

-- 
   Fabrízio de Royes Mello
   PostgreSQL Developer at OnGres Inc. - https://ongres.com