On Tue, Feb 23, 2021 at 8:54 PM Amit Kapila <amit.kapil...@gmail.com> wrote:
> 1. With respect to SQL APIs, currently 'two-phase-commit' is a plugin > option so it is possible that the first time when it gets changes > (pg_logical_slot_get_changes) *without* 2PC enabled it will not get > the prepared even though prepare is after consistent snapshot. Now > next time during getting changes (pg_logical_slot_get_changes) if the > 2PC option is enabled it will skip prepare because by that time > start_decoding_at has been moved. So the user will only get commit > prepared as shown in the example in the email above [2]. I think it > might be better to allow enable/disable of 2PC only at create_slot > time. Markus, Ajin, and I seem to be in agreement on this point. I > think the same will be true for subscriber-side solution as well. > Attaching a patch which avoids repeated decoding of prepares using the approach suggest by Andres. Added snapshot_was_exported_at_lsn; fields in ReplicationSlotPersistentData and SnapBuild which now stores the LSN at which the slot snapshot is exported the time it is created. This patch also modifies the API pg_create_logical_replication_slot() to take an extra parameter to enable two-phase commits and disables pg_logical_slot_get_changes() from enabling two-phase. I plan to split this into two patches next. But do review and let me know if you have any comments. regards, Ajin
v1-0001-Avoid-repeated-decoding-of-prepared-transactions.patch
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