logical decoding: old/newtuple in spooled UPDATE changes was switched around.

anarazel · anarazel · commit a50f50a65277 · 2016-03-05T18:02:20.000-08:00
Somehow I managed to flip the order of restoring old &amp; new tuples when
de-spooling a change in a large transaction from disk. This happens to
only take effect when a change is spooled to disk which has old/new
versions of the tuple. That only is the case for UPDATEs where he
primary key changed or where replica identity is changed to FULL.

The tests didn't catch this because either spooled updates, or updates
that changed primary keys, were tested; not both at the same time.

Found while adding tests for the following commit.

Backpatch: 9.4, where logical decoding was added
diff --git a/contrib/test_decoding/expected/ddl.out b/contrib/test_decoding/expected/ddl.out
@@ -196,6 +196,21 @@ ORDER BY 1,2;
  20467 | table public.tr_etoomuch: DELETE: id[integer]:1 | table public.tr_etoomuch: UPDATE: id[integer]:9999 data[integer]:-9999
 (3 rows)
 
+-- check updates of primary keys work correctly
+BEGIN;
+CREATE TABLE spoolme AS SELECT g.i FROM generate_series(1, 5000) g(i);
+UPDATE tr_etoomuch SET id = -id WHERE id = 5000;
+DELETE FROM spoolme;
+DROP TABLE spoolme;
+COMMIT;
+SELECT data
+FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
+WHERE data ~ 'UPDATE';
+                                                    data                                                     
+-------------------------------------------------------------------------------------------------------------
+ table public.tr_etoomuch: UPDATE: old-key: id[integer]:5000 new-tuple: id[integer]:-5000 data[integer]:5000
+(1 row)
+
 /*
  * check whether we decode subtransactions correctly in relation with each
  * other
diff --git a/contrib/test_decoding/sql/ddl.sql b/contrib/test_decoding/sql/ddl.sql
@@ -114,6 +114,18 @@ FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids',
 GROUP BY substring(data, 1, 24)
 ORDER BY 1,2;
 
+-- check updates of primary keys work correctly
+BEGIN;
+CREATE TABLE spoolme AS SELECT g.i FROM generate_series(1, 5000) g(i);
+UPDATE tr_etoomuch SET id = -id WHERE id = 5000;
+DELETE FROM spoolme;
+DROP TABLE spoolme;
+COMMIT;
+
+SELECT data
+FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1')
+WHERE data ~ 'UPDATE';
+
 /*
  * check whether we decode subtransactions correctly in relation with each
  * other
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
@@ -2266,29 +2266,29 @@ ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 		case REORDER_BUFFER_CHANGE_UPDATE:
 			/* fall through */
 		case REORDER_BUFFER_CHANGE_DELETE:
-			if (change->data.tp.newtuple)
+			if (change->data.tp.oldtuple)
 			{
 				Size		len = offsetof(ReorderBufferTupleBuf, data)
 				+((ReorderBufferTupleBuf *) data)->tuple.t_len
 				- offsetof(HeapTupleHeaderData, t_bits);
 
-				change->data.tp.newtuple = ReorderBufferGetTupleBuf(rb);
-				memcpy(change->data.tp.newtuple, data, len);
-				change->data.tp.newtuple->tuple.t_data =
-					&change->data.tp.newtuple->header;
+				change->data.tp.oldtuple = ReorderBufferGetTupleBuf(rb);
+				memcpy(change->data.tp.oldtuple, data, len);
+				change->data.tp.oldtuple->tuple.t_data =
+					&change->data.tp.oldtuple->header;
 				data += len;
 			}
 
-			if (change->data.tp.oldtuple)
+			if (change->data.tp.newtuple)
 			{
 				Size		len = offsetof(ReorderBufferTupleBuf, data)
 				+((ReorderBufferTupleBuf *) data)->tuple.t_len
 				- offsetof(HeapTupleHeaderData, t_bits);
 
-				change->data.tp.oldtuple = ReorderBufferGetTupleBuf(rb);
-				memcpy(change->data.tp.oldtuple, data, len);
-				change->data.tp.oldtuple->tuple.t_data =
-					&change->data.tp.oldtuple->header;
+				change->data.tp.newtuple = ReorderBufferGetTupleBuf(rb);
+				memcpy(change->data.tp.newtuple, data, len);
+				change->data.tp.newtuple->tuple.t_data =
+					&change->data.tp.newtuple->header;
 				data += len;
 			}
 			break;
