Fix publish_as_relid with multiple publications

tvondra · tvondra · commit 677a1dc0ca0f · 2022-03-16T18:06:27.000+01:00
Commit 83fd453 allowed publishing of changes via ancestors, for publications defined with publish_via_partition_root. But the way the ancestor was determined in get_rel_sync_entry() was incorrect, simply updating the same variable. So with multiple publications, replicating different ancestors, the outcome depended on the order of publications in the list - the value from the last loop was used, even if it wasn't the top-most ancestor. This is a probably rare situation, as in most cases publications do not overlap, so each partition has exactly one candidate ancestor to replicate as and there's no ambiguity. Fixed by tracking the "ancestor level" for each publication, and picking the top-most ancestor. Adds a test case, verifying the correct ancestor is used for publishing the changes and that this does not depend on order of publications in the list. Older releases have another bug in this loop - once all actions are replicated, the loop is terminated, on the assumption that inspecting additional publications is unecessary. But that misses the fact that those additional applications may replicate different ancestors. Fixed by removal of this break condition. We might still terminate the loop in some cases (e.g. when replicating all actions and the ancestor is the partition root). Backpatch to 13, where publish_via_partition_root was introduced. Initial report and fix by me, test added by Hou zj. Reviews and improvements by Amit Kapila. Author: Tomas Vondra, Hou zj, Amit Kapila Reviewed-by: Amit Kapila, Hou zj Discussion: https://postgr.es/m/d26d24dd-2fab-3c48-0162-2b7f84a9c893%40enterprisedb.com
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
@@ -1039,6 +1039,7 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 		List	   *pubids = GetRelationPublications(relid);
 		ListCell   *lc;
 		Oid			publish_as_relid = relid;
+		int			publish_ancestor_level = 0;
 		bool		am_partition = get_rel_relispartition(relid);
 		char		relkind = get_rel_relkind(relid);
 
@@ -1064,11 +1065,28 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 			Publication *pub = lfirst(lc);
 			bool		publish = false;
 
+			/*
+			 * Under what relid should we publish changes in this publication?
+			 * We'll use the top-most relid across all publications. Also track
+			 * the ancestor level for this publication.
+			 */
+			Oid			pub_relid = relid;
+			int			ancestor_level = 0;
+
+			/*
+			 * If this is a FOR ALL TABLES publication, pick the partition root
+			 * and set the ancestor level accordingly.
+			 */
 			if (pub->alltables)
 			{
 				publish = true;
 				if (pub->pubviaroot && am_partition)
-					publish_as_relid = llast_oid(get_partition_ancestors(relid));
+				{
+					List	   *ancestors = get_partition_ancestors(relid);
+
+					pub_relid = llast_oid(ancestors);
+					ancestor_level = list_length(ancestors);
+				}
 			}
 
 			if (!publish)
@@ -1085,6 +1103,7 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 				{
 					List	   *ancestors = get_partition_ancestors(relid);
 					ListCell   *lc2;
+					int			level = 0;
 
 					/*
 					 * Find the "topmost" ancestor that is in this
@@ -1094,12 +1113,17 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 					{
 						Oid			ancestor = lfirst_oid(lc2);
 
+						level++;
+
 						if (list_member_oid(GetRelationPublications(ancestor),
 											pub->oid))
 						{
 							ancestor_published = true;
 							if (pub->pubviaroot)
-								publish_as_relid = ancestor;
+							{
+								pub_relid = ancestor;
+								ancestor_level = level;
+							}
 						}
 					}
 				}
@@ -1120,11 +1144,21 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 				entry->pubactions.pubupdate |= pub->pubactions.pubupdate;
 				entry->pubactions.pubdelete |= pub->pubactions.pubdelete;
 				entry->pubactions.pubtruncate |= pub->pubactions.pubtruncate;
-			}
 
-			if (entry->pubactions.pubinsert && entry->pubactions.pubupdate &&
-				entry->pubactions.pubdelete && entry->pubactions.pubtruncate)
-				break;
+				/*
+				 * We want to publish the changes as the top-most ancestor
+				 * across all publications. So we need to check if the
+				 * already calculated level is higher than the new one. If
+				 * yes, we can ignore the new value (as it's a child).
+				 * Otherwise the new value is an ancestor, so we keep it.
+				 */
+				if (publish_ancestor_level > ancestor_level)
+					continue;
+
+				/* The new value is an ancestor, so let's keep it. */
+				publish_as_relid = pub_relid;
+				publish_ancestor_level = ancestor_level;
+			}
 		}
 
 		list_free(pubids);
diff --git a/src/test/subscription/t/013_partition.pl b/src/test/subscription/t/013_partition.pl
@@ -6,7 +6,7 @@
 use warnings;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 63;
+use Test::More tests => 67;
 
 # setup
 
@@ -409,6 +409,12 @@ BEGIN
 	"CREATE TABLE tab3 (a int PRIMARY KEY, b text) PARTITION BY LIST (a)");
 $node_publisher->safe_psql('postgres',
 	"CREATE TABLE tab3_1 PARTITION OF tab3 FOR VALUES IN (0, 1, 2, 3, 5, 6)");
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE tab4 (a int PRIMARY KEY) PARTITION BY LIST (a)");
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE tab4_1 PARTITION OF tab4 FOR VALUES IN (0, 1) PARTITION BY LIST (a)");
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE tab4_1_1 PARTITION OF tab4_1 FOR VALUES IN (0, 1)");
 $node_publisher->safe_psql('postgres',
 	"ALTER PUBLICATION pub_all SET (publish_via_partition_root = true)");
 # Note: tab3_1's parent is not in the publication, in which case its
@@ -418,6 +424,9 @@ BEGIN
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION pub_viaroot FOR TABLE tab2, tab2_1, tab3_1 WITH (publish_via_partition_root = true)"
 );
+$node_publisher->safe_psql('postgres',
+	"CREATE PUBLICATION pub_lower_level FOR TABLE tab4_1 WITH (publish_via_partition_root = true)"
+);
 
 # prepare data for the initial sync
 $node_publisher->safe_psql('postgres', "INSERT INTO tab2 VALUES (1)");
@@ -462,10 +471,16 @@ BEGIN
 $node_subscriber2->safe_psql('postgres',
 	"CREATE TABLE tab3_1 (a int PRIMARY KEY, c text DEFAULT 'sub2_tab3_1', b text)"
 );
+$node_subscriber2->safe_psql('postgres',
+	"CREATE TABLE tab4 (a int PRIMARY KEY)"
+);
+$node_subscriber2->safe_psql('postgres',
+	"CREATE TABLE tab4_1 (a int PRIMARY KEY)"
+);
 # Publication that sub2 points to now publishes via root, so must update
 # subscription target relations.
 $node_subscriber2->safe_psql('postgres',
-	"ALTER SUBSCRIPTION sub2 REFRESH PUBLICATION");
+	"ALTER SUBSCRIPTION sub2 SET PUBLICATION pub_lower_level, pub_all");
 
 # Wait for initial sync of all subscriptions
 $node_subscriber1->poll_query_until('postgres', $synced_query)
@@ -486,6 +501,8 @@ BEGIN
 	"INSERT INTO tab2 VALUES (0), (3), (5)");
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab3 VALUES (1), (0), (3), (5)");
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO tab4 VALUES (0)");
 
 $node_publisher->wait_for_catchup('sub_viaroot');
 $node_publisher->wait_for_catchup('sub2');
@@ -525,6 +542,42 @@ BEGIN
 sub2_tab3|3
 sub2_tab3|5), 'inserts into tab3 replicated');
 
+$result = $node_subscriber2->safe_psql('postgres',
+	"SELECT a FROM tab4 ORDER BY 1");
+is( $result, qq(0), 'inserts into tab4 replicated');
+
+$result = $node_subscriber2->safe_psql('postgres',
+	"SELECT a FROM tab4_1 ORDER BY 1");
+is( $result, qq(), 'inserts into tab4_1 replicated');
+
+# now switch the order of publications in the list, try again, the result
+# should be the same (no dependence on order of pulications)
+$node_subscriber2->safe_psql('postgres',
+	"ALTER SUBSCRIPTION sub2 SET PUBLICATION pub_all, pub_lower_level");
+
+# make sure the subscription on the second subscriber is synced, before
+# continuing
+$node_subscriber2->poll_query_until('postgres', $synced_query)
+  or die "Timed out while waiting for subscriber to synchronize data";
+
+# Insert a change into the leaf partition, should be replicated through
+# the partition root (thanks to the FOR ALL TABLES partition).
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO tab4 VALUES (1)");
+
+$node_publisher->wait_for_catchup('sub2');
+
+# tab4 change should be replicated through the root partition, which
+# maps to the tab4 relation on subscriber.
+$result = $node_subscriber2->safe_psql('postgres',
+	"SELECT a FROM tab4 ORDER BY 1");
+is( $result, qq(0
+1), 'inserts into tab4 replicated');
+
+$result = $node_subscriber2->safe_psql('postgres',
+	"SELECT a FROM tab4_1 ORDER BY 1");
+is( $result, qq(), 'inserts into tab4_1 replicated');
+
 # update (replicated as update)
 $node_publisher->safe_psql('postgres', "UPDATE tab1 SET a = 6 WHERE a = 5");
 $node_publisher->safe_psql('postgres', "UPDATE tab2 SET a = 6 WHERE a = 5");
