Fix construction of updated-columns bitmap in logical replication.

tglsfdc · tglsfdc · commit 39d6aec1927c · 2020-07-20T13:40:16.000-04:00
Commit b9c130a failed to apply the publisher-to-subscriber column mapping while checking which columns were updated. Perhaps less significantly, it didn't exclude dropped columns either. This could result in an incorrect updated-columns bitmap and thus wrong decisions about whether to fire column-specific triggers on the subscriber while applying updates. In HEAD (since commit 9de77b5), it could also result in accesses off the end of the colstatus array, as detected by buildfarm member skink. Fix the logic, and adjust 003_constraints.pl so that the problem is exposed in unpatched code. In HEAD, also add some assertions to check that we don't access off the ends of these newly variable-sized arrays. Back-patch to v10, as b9c130a was. Discussion: https://postgr.es/m/CAH2-Wz=79hKQ4++c5A060RYbjTHgiYTHz=fw6mptCtgghH2gJA@mail.gmail.com
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
@@ -745,9 +745,16 @@ apply_handle_update(StringInfo s)
 	target_rte = list_nth(estate->es_range_table, 0);
 	for (i = 0; i < remoteslot->tts_tupleDescriptor->natts; i++)
 	{
-		if (newtup.changed[i])
-			target_rte->updatedCols = bms_add_member(target_rte->updatedCols,
-													 i + 1 - FirstLowInvalidHeapAttributeNumber);
+		Form_pg_attribute att = TupleDescAttr(remoteslot->tts_tupleDescriptor, i);
+		int			remoteattnum = rel->attrmap[i];
+
+		if (!att->attisdropped && remoteattnum >= 0)
+		{
+			if (newtup.changed[remoteattnum])
+				target_rte->updatedCols =
+					bms_add_member(target_rte->updatedCols,
+								   i + 1 - FirstLowInvalidHeapAttributeNumber);
+		}
 	}
 
 	PushActiveSnapshot(GetTransactionSnapshot());
diff --git a/src/test/subscription/t/003_constraints.pl b/src/test/subscription/t/003_constraints.pl
@@ -19,14 +19,14 @@
 $node_publisher->safe_psql('postgres',
 	"CREATE TABLE tab_fk (bid int PRIMARY KEY);");
 $node_publisher->safe_psql('postgres',
-"CREATE TABLE tab_fk_ref (id int PRIMARY KEY, bid int REFERENCES tab_fk (bid));"
+"CREATE TABLE tab_fk_ref (id int PRIMARY KEY, junk text, bid int REFERENCES tab_fk (bid));"
 );
 
-# Setup structure on subscriber
+# Setup structure on subscriber; column order intentionally different
 $node_subscriber->safe_psql('postgres',
 	"CREATE TABLE tab_fk (bid int PRIMARY KEY);");
 $node_subscriber->safe_psql('postgres',
-"CREATE TABLE tab_fk_ref (id int PRIMARY KEY, bid int REFERENCES tab_fk (bid));"
+"CREATE TABLE tab_fk_ref (id int PRIMARY KEY, bid int REFERENCES tab_fk (bid), junk text);"
 );
 
 # Setup logical replication
@@ -47,8 +47,10 @@
 
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab_fk (bid) VALUES (1);");
+# "junk" value is meant to be large enough to force out-of-line storage
 $node_publisher->safe_psql('postgres',
-	"INSERT INTO tab_fk_ref (id, bid) VALUES (1, 1);");
+	"INSERT INTO tab_fk_ref (id, bid, junk) VALUES (1, 1, repeat(pi()::text,20000));"
+);
 
 $node_publisher->poll_query_until('postgres', $caughtup_query)
   or die "Timed out while waiting for subscriber to catch up";
@@ -136,7 +138,8 @@ BEGIN
 
 $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), min(id), max(id) FROM tab_fk_ref;");
-is($result, qq(2|1|2), 'check column trigger applied on even for other column');
+is($result, qq(2|1|2),
+	'check column trigger applied even on update for other column');
 
 $node_subscriber->stop('fast');
 $node_publisher->stop('fast');
