logical decoding: Tell reorderbuffer about all xids.

Logical decoding's reorderbuffer keeps transactions in an LSN ordered
list for efficiency. To make that's efficiently possible upper-level
xids are forced to be logged before nested subtransaction xids.  That
only works though if these records are all looked at: Unfortunately we
didn't do so for e.g. row level locks, which are otherwise uninteresting
for logical decoding.

This could lead to errors like:
"ERROR: subxact logged without previous toplevel record".

It's not sufficient to just look at row locking records, the xid could
appear first due to a lot of other types of records (which will trigger
the transaction to be marked logged with MarkCurrentTransactionIdLoggedIfAny).
So invent infrastructure to tell reorderbuffer about xids seen, when
they'd otherwise not pass through reorderbuffer.c.

Reported-By: Jarred Ward
Bug: #13844
Discussion: 20160105033249.1087.66040@wrigleys.postgresql.org
Backpatch: 9.4, where logical decoding was added

1 files changed, 13 insertions, 8 deletions

diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 478c3e874af..b3276c74c7c 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -1741,16 +1741,21 @@ ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
 
 
 /*
- * Check whether a transaction is already known in this module.xs
+ * Tell reorderbuffer about an xid seen in the WAL stream. Has to be called at
+ * least once for every xid in XLogRecord->xl_xid (other places in records
+ * may, but do not have to be passed through here).
+ *
+ * Reorderbuffer keeps some datastructures about transactions in LSN order,
+ * for efficiency. To do that it has to know about when transactions are seen
+ * first in the WAL. As many types of records are not actually interesting for
+ * logical decoding, they do not necessarily pass though here.
  */
-bool
-ReorderBufferIsXidKnown(ReorderBuffer *rb, TransactionId xid)
+void
+ReorderBufferProcessXid(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
 {
-	ReorderBufferTXN *txn;
-
-	txn = ReorderBufferTXNByXid(rb, xid, false, NULL, InvalidXLogRecPtr,
-								false);
-	return txn != NULL;
+	/* many records won't have an xid assigned, centralize check here */
+	if (xid != InvalidTransactionId)
+		ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
 }
 
 /*