Fix thinko introduced in 2bef06d et al.

anarazel · anarazel · commit d68742562ca4 · 2017-08-06T14:21:25.000-07:00
The callers for GetOldestSafeDecodingTransactionId() all inverted the argument for the argument introduced in 2bef06d. Luckily this appears to be inconsequential for the moment, as we wait for concurrent in-progress transaction when assembling a snapshot. Additionally this could only make a difference when adding a second logical slot, because only a pre-existing slot could cause an issue by lowering the returned xid dangerously much. Reported-By: Antonin Houska Discussion: https://postgr.es/m/32704.1496993134@localhost Backport: 9.4-, where 2bef06d was backpatched to.
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
@@ -327,7 +327,7 @@ CreateInitDecodingContext(char *plugin,
 	 */
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 
-	xmin_horizon = GetOldestSafeDecodingTransactionId(need_full_snapshot);
+	xmin_horizon = GetOldestSafeDecodingTransactionId(!need_full_snapshot);
 
 	slot->effective_catalog_xmin = xmin_horizon;
 	slot->data.catalog_xmin = xmin_horizon;
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
@@ -595,7 +595,7 @@ SnapBuildExportSnapshot(SnapBuild *builder)
 		TransactionId safeXid;
 
 		LWLockAcquire(ProcArrayLock, LW_SHARED);
-		safeXid = GetOldestSafeDecodingTransactionId(true);
+		safeXid = GetOldestSafeDecodingTransactionId(false);
 		LWLockRelease(ProcArrayLock);
 
 		Assert(TransactionIdPrecedesOrEquals(safeXid, snap->xmin));
