Horton

Re: Minimal logical decoding on standbys

Alvaro Herrera <alvherre@2ndquadrant.com>

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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Robert Haas <robertmhaas@gmail.com>, Sergei Kornilov <sk@zsrv.org>, Amit Khandekar <amitdkhan.pg@gmail.com>, tushar <tushar.ahuja@enterprisedb.com>, Petr Jelinek <petr.jelinek@2ndquadrant.com>, Craig Ringer <craig@2ndquadrant.com>, Petr Jelinek <petr@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-06-11T18:36:50Z
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 2019-May-23, Andres Freund wrote:

> On 2019-05-23 09:37:50 -0400, Robert Haas wrote:
> > On Thu, May 23, 2019 at 9:30 AM Sergei Kornilov <sk@zsrv.org> wrote:
> > > > wal_level is PGC_POSTMASTER.
> > >
> > > But primary can be restarted without restart on standby. We require wal_level replica or highter (currently only logical) on standby. So online change from logical to replica wal_level is possible on standby's controlfile.
> > 
> > That's true, but Amit's scenario involved a change in wal_level during
> > the execution of pg_create_logical_replication_slot(), which I think
> > can't happen.
> 
> I don't see why not - we're talking about the wal_level in the WAL
> stream, not the setting on the standby. And that can change during the
> execution of pg_create_logical_replication_slot(), if a PARAMTER_CHANGE
> record is replayed. I don't think it's actually a problem, as I
> outlined in my response to Amit, though.

I don't know if this is directly relevant, but in commit_ts.c we go to
great lengths to ensure that things continue to work across restarts and
changes of the GUC in the primary, by decoupling activation and
deactivation of the module from start-time initialization.  Maybe that
idea is applicable for this too?

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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