Horton

Re: Minimal logical decoding on standbys

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Jeff Davis <pgsql@j-davis.com>, Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Ibrar Ahmed <ibrar.ahmad@gmail.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, fabriziomello@gmail.com, tushar <tushar.ahuja@enterprisedb.com>, Rahila Syed <rahila.syed@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2023-04-04T07:48:39Z
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, Apr 4, 2023 at 10:55 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Tue, Apr 4, 2023 at 3:17 AM Drouvot, Bertrand
> <bertranddrouvot.pg@gmail.com> wrote:
> >
> > Hi,
> >
> > On 4/3/23 8:10 AM, Drouvot, Bertrand wrote:
> > > Hi,
> > >
> > > On 4/3/23 7:35 AM, Amit Kapila wrote:
> > >> On Mon, Apr 3, 2023 at 4:26 AM Jeff Davis <pgsql@j-davis.com> wrote:
> > >>
> > >> Agreed, even Bertrand and myself discussed the same approach few
> > >> emails above. BTW, if we have this selective logic to wake
> > >> physical/logical walsenders and for standby's, we only wake logical
> > >> walsenders at the time of  ApplyWalRecord() then do we need the new
> > >> conditional variable enhancement being discussed, and if so, why?
> > >>
> > >
> > > Thank you both for this new idea and discussion. In that case I don't think
> > > we need the new CV API and the use of a CV anymore. As just said up-thread I'll submit
> > > a new proposal with this new approach.
> > >
> >
> > Please find enclosed V57 implementing the new approach in 0004.
>
> Regarding 0004 patch:
>
> @@ -2626,6 +2626,12 @@ InitWalSenderSlot(void)
>                         walsnd->sync_standby_priority = 0;
>                         walsnd->latch = &MyProc->procLatch;
>                         walsnd->replyTime = 0;
> +
> +                       if (MyDatabaseId == InvalidOid)
> +                               walsnd->kind = REPLICATION_KIND_PHYSICAL;
> +                       else
> +                               walsnd->kind = REPLICATION_KIND_LOGICAL;
> +
>
> I think we might want to set the replication kind when processing the
> START_REPLICATION command. The walsender using a logical replication
> slot is not necessarily streaming (e.g. when COPYing table data).
>

Discussing with Bertrand off-list, it's wrong as the logical
replication slot creation also needs to read WAL records so a
walsender who is creating a logical replication slot needs to be woken
up. We can set it the replication kind when processing
START_REPLICATION and CREATE_REPLICATION_SLOT, but it seems better to
set it in one place. So I agree to set it in InitWalSenderSlot().

Regards,

-- 
Masahiko Sawada
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