Horton

Re: logical decoding and replication of sequences

Tomas Vondra <tomas.vondra@enterprisedb.com>

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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Peter Eisentraut <peter.eisentraut@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Petr Jelinek <petr.jelinek@enterprisedb.com>
Date: 2022-01-26T02:16:57Z
Lists: pgsql-hackers

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Hi,

Here's a rebased version of the patch series. I decided to go back to 
the version from 2021/12/14, which does not include the changes to WAL 
logging. So this has the same issue with nextval() now waiting for WAL 
flush (and/or sync replica), as demonstrated by occasional failures of 
the TAP test in 0003, but my reasoning is this:

1) This is a preexisting issue, affecting sequences in general. It's not 
related to this patch, really. The fix will be independent of this, and 
there's little reason to block the decoding until that happens.

2) We've discussed a couple ways to fix this in [1] - logging individual 
sequence increments, flushing everything right away, waiting for page 
LSN, etc. My opinion is we'll use some form of waiting for page LSN, but 
no matter what fix we use it'll have almost no impact on this patch. 
There might be minor changes to the test, but that's about it.

3) There are ways to stabilize the tests even without that - it's enough 
to generate a little bit of WAL / get XID, not just nextval(). But 
that's only for 0003 which I don't intend to commit yet, and 0001/0002 
have no problems at all.


regards

[1] 
https://www.postgresql.org/message-id/712cad46-a9c8-1389-aef8-faf0203c9be9@enterprisedb.com

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Commits

  1. Fix cache invalidation bug in recovery_prefetch.

  2. Revert "Logical decoding of sequences"

  3. Minor improvements in sequence decoding code and docs

  4. Handle sequences in preprocess_pubobj_list

  5. Update tab-completion for CREATE PUBLICATION with sequences

  6. Add decoding of sequences to built-in replication

  7. Stabilize test_decoding touching with sequences

  8. Call ReorderBufferProcessXid from sequence_decode

  9. Add decoding of sequences to test_decoding

  10. Replace Test::More plans with done_testing

  11. Logical decoding of sequences

  12. Respect permissions within logical replication.