Horton

Re: Minimal logical decoding on standbys

bdrouvotAWS <bdrouvot@amazon.com>

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From: "Drouvot, Bertrand" <bdrouvot@amazon.com>
To: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>
Cc: 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: 2022-02-25T09:34:58Z
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.

Hi,

On 10/28/21 11:07 PM, Andres Freund wrote:
> Hi,
>
> On 2021-10-28 16:24:22 -0400, Robert Haas wrote:
>> On Wed, Oct 27, 2021 at 2:56 AM Drouvot, Bertrand <bdrouvot@amazon.com> wrote:
>>> So you have in mind to check for XLogLogicalInfoActive() first, and if true, then open the relation and call
>>> RelationIsAccessibleInLogicalDecoding()?
>> I think 0001 is utterly unacceptable. We cannot add calls to
>> table_open() in low-level functions like this. Suppose for example
>> that _bt_getbuf() calls _bt_log_reuse_page() which with 0001 applied
>> would call get_rel_logical_catalog(). _bt_getbuf() will have acquired
>> a buffer lock on the page. The idea that it's safe to call
>> table_open() while holding a buffer lock cannot be taken seriously.
> Yes - that's pretty clearly a deadlock hazard. It shouldn't too hard to fix, I
> think. Possibly a bit more verbose than nice, but...
>
> Alternatively we could propagate the information whether a relcache entry is
> for a catalog from the table to the index. Then we'd not need to change the
> btree code to pass the table down.

+1 for the idea of propagating to the index. If that sounds good to you 
too, I can try to have a look at it.

Thanks Robert and Andres for the feedbacks you have done on the various 
sub-patches.

I've now in mind to work sub patch by sub patch (starting with 0001 
then) and move to the next one once we agree that the current one is 
"ready".

I think that could help us to get this new feature moving forward more 
"easily", what do you think?

Thanks

Bertrand