Re: pgsql: Preserve conflict-relevant data during logical replication.

On Wed, Jul 23, 2025 at 03:35:06AM +0000, Amit Kapila wrote:
> Preserve conflict-relevant data during logical replication.
>
> Logical replication requires reliable conflict detection to maintain data
> consistency across nodes. To achieve this, we must prevent premature
> removal of tuples deleted by other origins and their associated commit_ts
> data by VACUUM, which could otherwise lead to incorrect conflict reporting
> and resolution.

Some of the tests added by this commit are causing blurps in the CI:
https://cfbot.cputube.org/highlights/all.html

Example of one job (triggered it once myself with a separate patch):
https://cirrus-ci.com/task/5397273342902272
[21:15:03.131](0.028s) not ok 7 - altering retain_dead_tuples is
allowed for disabled subscription
[21:18:48.295](225.164s) # poll_query_until timed out executing this
query:
[21:18:48.296](0.000s) not ok 8 - the xmin value of slot
'pg_conflict_detection' is valid on Node A
[21:18:48.306](0.010s) not ok 9 - warn of the possibility of receiving
changes from origins other than the publisher
[21:18:48.412](0.037s) not ok 11 - the deleted column is non-removable
[21:22:29.286](220.874s) # poll_query_until timed out executing this
query:
[21:22:29.287](0.000s) not ok 12 - the xmin value of slot
'pg_conflict_detection' is updated on Node A
[21:22:29.297](0.010s) not ok 13 - the deleted column is removed

The failures happen on FreeBSD as far as I know, that enforces some
rules not used elsewhere:
-c debug_copy_parse_plan_trees=on
-c debug_write_read_parse_plan_trees=on
-c debug_raw_expression_coverage_test=on
-c debug_parallel_query=regress
[...]
CPPFLAGS: -DRELCACHE_FORCE_RELEASE -DENFORCE_REGRESSION_TEST_NAME_RESTRICTIONS

I suspect that reusing these options would help in reproducing the
problem. These are not commonly used in buildfarm animals, reducing
the friction to make the instability show up.
--
Michael