Re: Minimal logical decoding on standbys

Bertrand Drouvot <bertranddrouvot.pg@gmail.com>

From: "Drouvot, Bertrand" <bertranddrouvot.pg@gmail.com>

To: Amit Kapila <amit.kapila16@gmail.com>

Cc: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, Jeff Davis <pgsql@j-davis.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>, Melanie Plageman <melanieplageman@gmail.com>

Date: 2023-04-04T09:42:45Z

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 →

Reduce the log level in 035_standby_logical_decoding.pl.
- 3034dc56ef4b 16.0 landed
035_standby_logical_decoding: Add missing waits for replication
- 57411c82ce86 16.0 landed
For cascading replication, wake physical and logical walsenders separately
- e101dfac3a53 16.0 landed
Handle logical slot conflicts on standby
- 26669757b6a7 16.0 landed
Support invalidating replication slots due to horizon and wal_level
- be87200efd93 16.0 landed
Prevent use of invalidated logical slot in CreateDecodingContext()
- 4397abd0a2af 16.0 landed
Replace replication slot's invalidated_at LSN with an enum
- 15f8203a5975 16.0 landed
Pass down table relation into more index relation functions
- 61b313e47eb9 16.0 landed
Assert only valid flag bits are passed to visibilitymap_set()
- a88a18b1250b 16.0 landed
Remove unused _bt_delitems_delete() argument.
- dc43492e46c7 14.0 cited
Add xl_btree_delete optimization.
- d2e5e20e5711 13.0 cited

Attachments

v58-0006-Doc-changes-describing-details-about-logical-dec.patch (text/plain) patch v58-0006
v58-0005-New-TAP-test-for-logical-decoding-on-standby.patch (text/plain) patch v58-0005
v58-0004-Fixing-Walsender-corner-case-with-logical-decodi.patch (text/plain) patch v58-0004
v58-0003-Allow-logical-decoding-on-standby.patch (text/plain) patch v58-0003
v58-0002-Arrange-for-a-new-pg_stat_database_conflicts-and.patch (text/plain) patch v58-0002
v58-0001-Handle-logical-slot-conflicts-on-standby.patch (text/plain) patch v58-0001

Hi,

On 4/4/23 7:57 AM, Amit Kapila wrote:
> On Mon, Apr 3, 2023 at 8:51 PM Drouvot, Bertrand
> <bertranddrouvot.pg@gmail.com> wrote:
>>
>> I made it as simple as:
>>
>>           /*
>>            * If the slot is already invalid or is a non conflicting slot, we don't
>>            * need to do anything.
>>            */
>>           islogical = xid ? true : false;
>>
>>           if (SlotIsInvalid(s, islogical) || SlotIsNotConflicting(s, islogical, xid, &oldestLSN))
>>
>> in V56 attached.
>>
> 
> Here the variable 'islogical' doesn't seem to convey its actual
> meaning because one can imagine that it indicates whether the slot is
> logical which I don't think is the actual intent.

Good point. Just renamed it to 'check_on_xid' (as still needed outside of
the "CanInvalidateSlot" context) in V58 attached.

> One idea to simplify
> this is to introduce a single function CanInvalidateSlot() or
> something like that and move the logic from both the functions
> SlotIsInvalid() and SlotIsNotConflicting() into the new function.
> 

Oh right, even better, thanks!
Done in V58 and now this is as simple as:

+               if (DoNotInvalidateSlot(s, xid, &oldestLSN))
                 {
                         /* then, we are not forcing for invalidation */


Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com