Horton

RE: long-standing data loss bug in initial sync of logical replication

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Shlok Kyal' <shlok.kyal.oss@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, vignesh C <vignesh21@gmail.com>, Nitin Motiani <nitinmotiani@google.com>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Amit Kapila <amit.kapila16@gmail.com>
Date: 2024-09-30T10:03:42Z
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. Fix typo in test file name added in commit 4909b38af0.

  2. Fix data loss in logical replication.

  3. Avoid invalidating all RelationSyncCache entries on publication rename.

  4. Remove obsolete RECHECK keyword completely

  5. Backport BackgroundPsql perl test module

Dear Shlok,

> I have addressed the comment for 0002 patch and attached the patches.
> Also, I have moved the tests in the 0002 to 0001 patch.

Thanks for updating the patch. 0002 patch seems to remove cache invalidations
from publication_invalidation_cb(). Related with it, I found an issue and had a concern.

1.
The replication continues even after ALTER PUBLICATION RENAME is executed.
For example - assuming that a subscriber subscribes only "pub":

```
pub=# INSERT INTO tab values (1);
INSERT 0 1
pub=# ALTER PUBLICATION pub RENAME TO pub1;
ALTER PUBLICATION
pub=# INSERT INTO tab values (2);
INSERT 0 1

sub=# SELECT * FROM tab ; -- (2) should not be replicated however...
 a 
---
 1
 2
(2 rows)
```

This happens because 1) ALTER PUBLICATION RENAME statement won't be invalidate the
relation cache, and 2) publications are reloaded only when invalid RelationSyncEntry
is found. In given example, the first INSERT creates the valid cache and second
INSERT reuses it. Therefore, the pubname-check is skipped.

For now, the actual renaming is done at AlterObjectRename_internal(), a generic
function. I think we must implement a dedecated function to publication and must
invalidate relcaches there.

2.
Similarly with above, the relcache won't be invalidated when ALTER PUBLICATION
OWNER TO is executed. This means that privilage checks may be ignored if the entry
is still valid. Not sure, but is there a possibility this causes an inconsistency?

Best regards,
Hayato Kuroda
FUJITSU LIMITED