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Add option to enable two_phase commits via pg_create_logical_replication_slot.

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Commit 0aa8a01d04 extends the output plugin API to allow decoding of
prepared xacts and allowed the user to enable/disable the two-phase option
via pg_logical_slot_get_changes(). This can lead to a problem such that
the first time when it gets changes via pg_logical_slot_get_changes()
without two_phase option enabled it will not get the prepared even though
prepare is after consistent snapshot. Now next time during getting changes,
if the two_phase option is enabled it can skip prepare because by that
time start decoding point has been moved. So the user will only get commit
prepared.

Allow to enable/disable this option at the create slot time and default
will be false. It will break the existing slots which is fine in a major
release.

Author: Ajin Cherian
Reviewed-by: Amit Kapila and Vignesh C
Discussion: https://postgr.es/m/d0f60d60-133d-bf8d-bd70-47784d8fabf3@enterprisedb.com
This commit is contained in:
Amit Kapila
2021-03-03 07:28:43 +05:30
parent ee28cacf61
commit 19890a064e
20 changed files with 131 additions and 93 deletions
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10
src/backend/replication/slot.c
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@@ -216,10 +216,17 @@ ReplicationSlotValidateName(const char *name, int elevel)
* name: Name of the slot
* db_specific: logical decoding is db specific; if the slot is going to
* be used for that pass true, otherwise false.
* two_phase: Allows decoding of prepared transactions. We allow this option
* to be enabled only at the slot creation time. If we allow this option
* to be changed during decoding then it is quite possible that we skip
* prepare first time because this option was not enabled. Now next time
* during getting changes, if the two_phase option is enabled it can skip
* prepare because by that time start decoding point has been moved. So the
* user will only get commit prepared.
*/
void
ReplicationSlotCreate(const char *name, bool db_specific,
ReplicationSlotPersistency persistency)
ReplicationSlotPersistency persistency, bool two_phase)
{
ReplicationSlot *slot = NULL;
int i;
@@ -277,6 +284,7 @@ ReplicationSlotCreate(const char *name, bool db_specific,
namestrcpy(&slot->data.name, name);
slot->data.database = db_specific ? MyDatabaseId : InvalidOid;
slot->data.persistency = persistency;
slot->data.two_phase = two_phase;
/* and then data only present in shared memory */
slot->just_dirtied = false;