Improve citus_shard_sizes performance in release-11.3 (#7051)

This PR combines the relevant parts of #7003, #7018 and the PR that
backports those changes to 11.3, #7050 to merge into the 11.3 release
branch.

This PR backports the changes to 11.3 release branch, there is another
PR, #7062, for 12.0 release branch and one, #7050, for main branch.

The commits are:
613cced1ae
772d194357

src/backend/distributed/citus.control

@@ -1,6 +1,6 @@
 # Citus extension
 comment = 'Citus distributed database'
-default_version = '11.3-1'
+default_version = '11.3-2'
 module_pathname = '$libdir/citus'
 relocatable = false
 schema = pg_catalog

src/backend/distributed/metadata/metadata_utility.c

@@ -91,7 +91,8 @@ static bool DistributedTableSizeOnWorker(WorkerNode *workerNode, Oid relationId,
 										 SizeQueryType sizeQueryType, bool failOnError,
 										 uint64 *tableSize);
 static List * ShardIntervalsOnWorkerGroup(WorkerNode *workerNode, Oid relationId);
-static char * GenerateShardStatisticsQueryForShardList(List *shardIntervalList);
+static char * GenerateShardIdNameValuesForShardList(List *shardIntervalList,
+													bool firstValue);
 static char * GenerateSizeQueryForRelationNameList(List *quotedShardNames,
 												   char *sizeFunction);
 static char * GetWorkerPartitionedSizeUDFNameBySizeQueryType(SizeQueryType sizeQueryType);
@@ -101,10 +102,10 @@ static char * GenerateAllShardStatisticsQueryForNode(WorkerNode *workerNode,
 static List * GenerateShardStatisticsQueryList(List *workerNodeList, List *citusTableIds);
 static void ErrorIfNotSuitableToGetSize(Oid relationId);
 static List * OpenConnectionToNodes(List *workerNodeList);
-static void ReceiveShardNameAndSizeResults(List *connectionList,
+static void ReceiveShardIdAndSizeResults(List *connectionList,
-										   Tuplestorestate *tupleStore,
+										 Tuplestorestate *tupleStore,
-										   TupleDesc tupleDescriptor);
+										 TupleDesc tupleDescriptor);
-static void AppendShardSizeQuery(StringInfo selectQuery, ShardInterval *shardInterval);
+static void AppendShardIdNameValues(StringInfo selectQuery, ShardInterval *shardInterval);
 
 static HeapTuple CreateDiskSpaceTuple(TupleDesc tupleDesc, uint64 availableBytes,
 									  uint64 totalBytes);
@@ -253,7 +254,7 @@ GetNodeDiskSpaceStatsForConnection(MultiConnection *connection, uint64 *availabl
 
 
 /*
- * citus_shard_sizes returns all shard names and their sizes.
+ * citus_shard_sizes returns all shard ids and their sizes.
  */
 Datum
 citus_shard_sizes(PG_FUNCTION_ARGS)
@@ -271,7 +272,7 @@ citus_shard_sizes(PG_FUNCTION_ARGS)
 	TupleDesc tupleDescriptor = NULL;
 	Tuplestorestate *tupleStore = SetupTuplestore(fcinfo, &tupleDescriptor);
 
-	ReceiveShardNameAndSizeResults(connectionList, tupleStore, tupleDescriptor);
+	ReceiveShardIdAndSizeResults(connectionList, tupleStore, tupleDescriptor);
 
 	PG_RETURN_VOID();
 }
@@ -446,12 +447,12 @@ GenerateShardStatisticsQueryList(List *workerNodeList, List *citusTableIds)
 
 
 /*
- * ReceiveShardNameAndSizeResults receives shard name and size results from the given
+ * ReceiveShardIdAndSizeResults receives shard id and size results from the given
  * connection list.
  */
 static void
-ReceiveShardNameAndSizeResults(List *connectionList, Tuplestorestate *tupleStore,
+ReceiveShardIdAndSizeResults(List *connectionList, Tuplestorestate *tupleStore,
-							   TupleDesc tupleDescriptor)
+							 TupleDesc tupleDescriptor)
 {
 	MultiConnection *connection = NULL;
 	foreach_ptr(connection, connectionList)
@@ -488,13 +489,9 @@ ReceiveShardNameAndSizeResults(List *connectionList, Tuplestorestate *tupleStore
 			memset(values, 0, sizeof(values));
 			memset(isNulls, false, sizeof(isNulls));
 
-			/* format is [0] shard id, [1] shard name, [2] size */
+			/* format is [0] shard id, [1] size */
-			char *tableName = PQgetvalue(result, rowIndex, 1);
+			values[0] = ParseIntField(result, rowIndex, 0);
-			Datum resultStringDatum = CStringGetDatum(tableName);
+			values[1] = ParseIntField(result, rowIndex, 1);
-			Datum textDatum = DirectFunctionCall1(textin, resultStringDatum);
-
-			values[0] = textDatum;
-			values[1] = ParseIntField(result, rowIndex, 2);
 
 			tuplestore_putvalues(tupleStore, tupleDescriptor, values, isNulls);
 		}
@@ -920,6 +917,12 @@ static char *
 GenerateAllShardStatisticsQueryForNode(WorkerNode *workerNode, List *citusTableIds)
 {
 	StringInfo allShardStatisticsQuery = makeStringInfo();
+	bool insertedValues = false;
+
+	appendStringInfoString(allShardStatisticsQuery, "SELECT shard_id, ");
+	appendStringInfo(allShardStatisticsQuery, PG_TOTAL_RELATION_SIZE_FUNCTION,
+					 "table_name");
+	appendStringInfoString(allShardStatisticsQuery, " FROM (VALUES ");
 
 	Oid relationId = InvalidOid;
 	foreach_oid(relationId, citusTableIds)
@@ -934,34 +937,49 @@ GenerateAllShardStatisticsQueryForNode(WorkerNode *workerNode, List *citusTableI
 		{
 			List *shardIntervalsOnNode = ShardIntervalsOnWorkerGroup(workerNode,
 																	 relationId);
-			char *shardStatisticsQuery =
+			if (list_length(shardIntervalsOnNode) == 0)
-				GenerateShardStatisticsQueryForShardList(shardIntervalsOnNode);
+			{
-			appendStringInfoString(allShardStatisticsQuery, shardStatisticsQuery);
+				relation_close(relation, AccessShareLock);
+				continue;
+			}
+			char *shardIdNameValues =
+				GenerateShardIdNameValuesForShardList(shardIntervalsOnNode,
+													  !insertedValues);
+			insertedValues = true;
+			appendStringInfoString(allShardStatisticsQuery, shardIdNameValues);
 			relation_close(relation, AccessShareLock);
 		}
 	}
 
-	/* Add a dummy entry so that UNION ALL doesn't complain */
+	if (!insertedValues)
-	appendStringInfo(allShardStatisticsQuery, "SELECT 0::bigint, NULL::text, 0::bigint;");
+	{
+		return "SELECT 0 AS shard_id, '' AS table_name LIMIT 0";
+	}
 
+	appendStringInfoString(allShardStatisticsQuery, ") t(shard_id, table_name) "
+													"WHERE to_regclass(table_name) IS NOT NULL");
 	return allShardStatisticsQuery->data;
 }
 
 
 /*
- * GenerateShardStatisticsQueryForShardList generates a query that returns:
+ * GenerateShardIdNameValuesForShardList generates a list of (shard_id, shard_name) values
- * SELECT shard_id, shard_name, shard_size for all shards in the list
+ * for all shards in the list
  */
 static char *
-GenerateShardStatisticsQueryForShardList(List *shardIntervalList)
+GenerateShardIdNameValuesForShardList(List *shardIntervalList, bool firstValue)
 {
 	StringInfo selectQuery = makeStringInfo();
 
 	ShardInterval *shardInterval = NULL;
 	foreach_ptr(shardInterval, shardIntervalList)
 	{
-		AppendShardSizeQuery(selectQuery, shardInterval);
+		if (!firstValue)
-		appendStringInfo(selectQuery, " UNION ALL ");
+		{
+			appendStringInfoString(selectQuery, ", ");
+		}
+		firstValue = false;
+		AppendShardIdNameValues(selectQuery, shardInterval);
 	}
 
 	return selectQuery->data;
@@ -969,11 +987,10 @@ GenerateShardStatisticsQueryForShardList(List *shardIntervalList)
 
 
 /*
- * AppendShardSizeQuery appends a query in the following form to selectQuery
+ * AppendShardIdNameValues appends (shard_id, shard_name) for shard
- * SELECT shard_id, shard_name, shard_size
  */
 static void
-AppendShardSizeQuery(StringInfo selectQuery, ShardInterval *shardInterval)
+AppendShardIdNameValues(StringInfo selectQuery, ShardInterval *shardInterval)
 {
 	uint64 shardId = shardInterval->shardId;
 	Oid schemaId = get_rel_namespace(shardInterval->relationId);
@@ -985,9 +1002,7 @@ AppendShardSizeQuery(StringInfo selectQuery, ShardInterval *shardInterval)
 	char *shardQualifiedName = quote_qualified_identifier(schemaName, shardName);
 	char *quotedShardName = quote_literal_cstr(shardQualifiedName);
 
-	appendStringInfo(selectQuery, "SELECT " UINT64_FORMAT " AS shard_id, ", shardId);
+	appendStringInfo(selectQuery, "(" UINT64_FORMAT ", %s)", shardId, quotedShardName);
-	appendStringInfo(selectQuery, "%s AS shard_name, ", quotedShardName);
-	appendStringInfo(selectQuery, PG_TOTAL_RELATION_SIZE_FUNCTION, quotedShardName);
 }
 
 

src/backend/distributed/operations/stage_protocol.c

@@ -855,7 +855,7 @@ ProcessShardStatisticsRow(PGresult *result, int64 rowIndex, uint64 *shardId,
 		return false;
 	}
 
-	*shardSize = ParseIntField(result, rowIndex, 2);
+	*shardSize = ParseIntField(result, rowIndex, 1);
 	return true;
 }
 

src/backend/distributed/sql/citus--11.3-1--11.3-2.sql

@@ -0,0 +1,9 @@
+DROP VIEW citus_shards;
+DROP VIEW IF EXISTS pg_catalog.citus_tables;
+DROP VIEW IF EXISTS public.citus_tables;
+DROP FUNCTION citus_shard_sizes;
+
+#include "udfs/citus_shard_sizes/11.3-2.sql"
+
+#include "udfs/citus_shards/11.3-2.sql"
+#include "udfs/citus_tables/11.3-2.sql"

src/backend/distributed/sql/downgrades/citus--11.3-2--11.3-1.sql

@@ -0,0 +1,13 @@
+DROP VIEW IF EXISTS public.citus_tables;
+DROP VIEW IF EXISTS pg_catalog.citus_tables;
+
+DROP VIEW pg_catalog.citus_shards;
+DROP FUNCTION pg_catalog.citus_shard_sizes;
+#include "../udfs/citus_shard_sizes/10.0-1.sql"
+-- citus_shards/11.1-1.sql tries to create citus_shards in pg_catalog but it is not allowed.
+-- Here we use citus_shards/10.0-1.sql to properly create the view in citus schema and
+-- then alter it to pg_catalog, so citus_shards/11.1-1.sql can REPLACE it without any errors.
+#include "../udfs/citus_shards/10.0-1.sql"
+
+#include "../udfs/citus_tables/11.1-1.sql"
+#include "../udfs/citus_shards/11.1-1.sql"

src/backend/distributed/sql/udfs/citus_shard_sizes/11.3-2.sql

@@ -0,0 +1,6 @@
+CREATE OR REPLACE FUNCTION pg_catalog.citus_shard_sizes(OUT shard_id int, OUT size bigint)
+  RETURNS SETOF RECORD
+  LANGUAGE C STRICT
+  AS 'MODULE_PATHNAME', $$citus_shard_sizes$$;
+ COMMENT ON FUNCTION pg_catalog.citus_shard_sizes(OUT shard_id int, OUT size bigint)
+     IS 'returns shards sizes across citus cluster';

src/backend/distributed/sql/udfs/citus_shard_sizes/latest.sql

@@ -1,6 +1,6 @@
-CREATE FUNCTION pg_catalog.citus_shard_sizes(OUT table_name text, OUT size bigint)
+CREATE OR REPLACE FUNCTION pg_catalog.citus_shard_sizes(OUT shard_id int, OUT size bigint)
   RETURNS SETOF RECORD
   LANGUAGE C STRICT
   AS 'MODULE_PATHNAME', $$citus_shard_sizes$$;
- COMMENT ON FUNCTION pg_catalog.citus_shard_sizes(OUT table_name text, OUT size bigint)
+ COMMENT ON FUNCTION pg_catalog.citus_shard_sizes(OUT shard_id int, OUT size bigint)
      IS 'returns shards sizes across citus cluster';

src/backend/distributed/sql/udfs/citus_shards/11.3-2.sql

@@ -0,0 +1,46 @@
+CREATE OR REPLACE VIEW citus.citus_shards AS
+SELECT
+     pg_dist_shard.logicalrelid AS table_name,
+     pg_dist_shard.shardid,
+     shard_name(pg_dist_shard.logicalrelid, pg_dist_shard.shardid) as shard_name,
+     CASE WHEN partkey IS NOT NULL THEN 'distributed' WHEN repmodel = 't' THEN 'reference' ELSE 'local' END AS citus_table_type,
+     colocationid AS colocation_id,
+     pg_dist_node.nodename,
+     pg_dist_node.nodeport,
+     size as shard_size
+FROM
+   pg_dist_shard
+JOIN
+   pg_dist_placement
+ON
+   pg_dist_shard.shardid = pg_dist_placement.shardid
+JOIN
+   pg_dist_node
+ON
+   pg_dist_placement.groupid = pg_dist_node.groupid
+JOIN
+   pg_dist_partition
+ON
+   pg_dist_partition.logicalrelid = pg_dist_shard.logicalrelid
+LEFT JOIN
+   (SELECT shard_id, max(size) as size from citus_shard_sizes() GROUP BY shard_id) as shard_sizes
+ON
+    pg_dist_shard.shardid = shard_sizes.shard_id
+WHERE
+   pg_dist_placement.shardstate = 1
+AND
+   -- filter out tables owned by extensions
+   pg_dist_partition.logicalrelid NOT IN (
+      SELECT
+         objid
+      FROM
+         pg_depend
+      WHERE
+         classid = 'pg_class'::regclass AND refclassid = 'pg_extension'::regclass AND deptype = 'e'
+   )
+ORDER BY
+   pg_dist_shard.logicalrelid::text, shardid
+;
+
+ALTER VIEW citus.citus_shards SET SCHEMA pg_catalog;
+GRANT SELECT ON pg_catalog.citus_shards TO public;

src/backend/distributed/sql/udfs/citus_shards/latest.sql

@@ -1,4 +1,4 @@
-CREATE OR REPLACE VIEW pg_catalog.citus_shards AS
+CREATE OR REPLACE VIEW citus.citus_shards AS
 SELECT
      pg_dist_shard.logicalrelid AS table_name,
      pg_dist_shard.shardid,
@@ -23,7 +23,7 @@ JOIN
 ON
    pg_dist_partition.logicalrelid = pg_dist_shard.logicalrelid
 LEFT JOIN
-   (SELECT (regexp_matches(table_name,'_(\d+)$'))[1]::int as shard_id, max(size) as size from citus_shard_sizes() GROUP BY shard_id) as shard_sizes
+   (SELECT shard_id, max(size) as size from citus_shard_sizes() GROUP BY shard_id) as shard_sizes
 ON
     pg_dist_shard.shardid = shard_sizes.shard_id
 WHERE
@@ -42,4 +42,5 @@ ORDER BY
    pg_dist_shard.logicalrelid::text, shardid
 ;
 
+ALTER VIEW citus.citus_shards SET SCHEMA pg_catalog;
 GRANT SELECT ON pg_catalog.citus_shards TO public;

src/backend/distributed/sql/udfs/citus_tables/11.3-2.sql

@@ -0,0 +1,55 @@
+DO $$
+declare
+citus_tables_create_query text;
+BEGIN
+citus_tables_create_query=$CTCQ$
+    CREATE OR REPLACE VIEW %I.citus_tables AS
+    SELECT
+        logicalrelid AS table_name,
+        CASE WHEN partkey IS NOT NULL THEN 'distributed' ELSE
+            CASE when repmodel = 't' THEN 'reference' ELSE 'local' END
+        END AS citus_table_type,
+        coalesce(column_to_column_name(logicalrelid, partkey), '<none>') AS distribution_column,
+        colocationid AS colocation_id,
+        pg_size_pretty(table_sizes.table_size) AS table_size,
+        (select count(*) from pg_dist_shard where logicalrelid = p.logicalrelid) AS shard_count,
+        pg_get_userbyid(relowner) AS table_owner,
+        amname AS access_method
+    FROM
+        pg_dist_partition p
+    JOIN
+        pg_class c ON (p.logicalrelid = c.oid)
+    LEFT JOIN
+        pg_am a ON (a.oid = c.relam)
+    JOIN
+        (
+            SELECT ds.logicalrelid AS table_id, SUM(css.size) AS table_size
+            FROM citus_shard_sizes() css, pg_dist_shard ds
+            WHERE css.shard_id = ds.shardid
+            GROUP BY ds.logicalrelid
+        ) table_sizes ON (table_sizes.table_id = p.logicalrelid)
+    WHERE
+        -- filter out tables owned by extensions
+        logicalrelid NOT IN (
+            SELECT
+                objid
+            FROM
+                pg_depend
+            WHERE
+                classid = 'pg_class'::regclass AND refclassid = 'pg_extension'::regclass AND deptype = 'e'
+        )
+    ORDER BY
+        logicalrelid::text;
+$CTCQ$;
+
+IF EXISTS (SELECT 1 FROM pg_namespace WHERE nspname = 'public') THEN
+    EXECUTE format(citus_tables_create_query, 'public');
+    GRANT SELECT ON public.citus_tables TO public;
+ELSE
+    EXECUTE format(citus_tables_create_query, 'citus');
+    ALTER VIEW citus.citus_tables SET SCHEMA pg_catalog;
+    GRANT SELECT ON pg_catalog.citus_tables TO public;
+END IF;
+
+END;
+$$;

src/backend/distributed/sql/udfs/citus_tables/latest.sql

@@ -11,7 +11,7 @@ citus_tables_create_query=$CTCQ$
         END AS citus_table_type,
         coalesce(column_to_column_name(logicalrelid, partkey), '<none>') AS distribution_column,
         colocationid AS colocation_id,
-        pg_size_pretty(citus_total_relation_size(logicalrelid, fail_on_error := false)) AS table_size,
+        pg_size_pretty(table_sizes.table_size) AS table_size,
         (select count(*) from pg_dist_shard where logicalrelid = p.logicalrelid) AS shard_count,
         pg_get_userbyid(relowner) AS table_owner,
         amname AS access_method
@@ -21,6 +21,13 @@ citus_tables_create_query=$CTCQ$
         pg_class c ON (p.logicalrelid = c.oid)
     LEFT JOIN
         pg_am a ON (a.oid = c.relam)
+    JOIN
+        (
+            SELECT ds.logicalrelid AS table_id, SUM(css.size) AS table_size
+            FROM citus_shard_sizes() css, pg_dist_shard ds
+            WHERE css.shard_id = ds.shardid
+            GROUP BY ds.logicalrelid
+        ) table_sizes ON (table_sizes.table_id = p.logicalrelid)
     WHERE
         -- filter out tables owned by extensions
         logicalrelid NOT IN (

src/include/distributed/metadata_utility.h

@@ -41,7 +41,7 @@
 #define WORKER_PARTITIONED_RELATION_TOTAL_SIZE_FUNCTION \
 	"worker_partitioned_relation_total_size(%s)"
 
-#define SHARD_SIZES_COLUMN_COUNT (3)
+#define SHARD_SIZES_COLUMN_COUNT (2)
 
 /*
  * Flag to keep track of whether the process is currently in a function converting the

src/test/regress/expected/citus_update_table_statistics.out

@@ -64,11 +64,11 @@ SET citus.multi_shard_modify_mode TO sequential;
 SELECT citus_update_table_statistics('test_table_statistics_hash');
 NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
-NOTICE:  issuing SELECT 981000 AS shard_id, 'public.test_table_statistics_hash_981000' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981000') UNION ALL SELECT 981001 AS shard_id, 'public.test_table_statistics_hash_981001' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981001') UNION ALL SELECT 981002 AS shard_id, 'public.test_table_statistics_hash_981002' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981002') UNION ALL SELECT 981003 AS shard_id, 'public.test_table_statistics_hash_981003' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981003') UNION ALL SELECT 981004 AS shard_id, 'public.test_table_statistics_hash_981004' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981004') UNION ALL SELECT 981005 AS shard_id, 'public.test_table_statistics_hash_981005' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981005') UNION ALL SELECT 981006 AS shard_id, 'public.test_table_statistics_hash_981006' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981006') UNION ALL SELECT 981007 AS shard_id, 'public.test_table_statistics_hash_981007' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981007') UNION ALL SELECT 0::bigint, NULL::text, 0::bigint;
+NOTICE:  issuing SELECT shard_id, pg_total_relation_size(table_name) FROM (VALUES (981000, 'public.test_table_statistics_hash_981000'), (981001, 'public.test_table_statistics_hash_981001'), (981002, 'public.test_table_statistics_hash_981002'), (981003, 'public.test_table_statistics_hash_981003'), (981004, 'public.test_table_statistics_hash_981004'), (981005, 'public.test_table_statistics_hash_981005'), (981006, 'public.test_table_statistics_hash_981006'), (981007, 'public.test_table_statistics_hash_981007')) t(shard_id, table_name) WHERE to_regclass(table_name) IS NOT NULL
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
 NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
-NOTICE:  issuing SELECT 981000 AS shard_id, 'public.test_table_statistics_hash_981000' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981000') UNION ALL SELECT 981001 AS shard_id, 'public.test_table_statistics_hash_981001' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981001') UNION ALL SELECT 981002 AS shard_id, 'public.test_table_statistics_hash_981002' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981002') UNION ALL SELECT 981003 AS shard_id, 'public.test_table_statistics_hash_981003' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981003') UNION ALL SELECT 981004 AS shard_id, 'public.test_table_statistics_hash_981004' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981004') UNION ALL SELECT 981005 AS shard_id, 'public.test_table_statistics_hash_981005' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981005') UNION ALL SELECT 981006 AS shard_id, 'public.test_table_statistics_hash_981006' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981006') UNION ALL SELECT 981007 AS shard_id, 'public.test_table_statistics_hash_981007' AS shard_name, pg_total_relation_size('public.test_table_statistics_hash_981007') UNION ALL SELECT 0::bigint, NULL::text, 0::bigint;
+NOTICE:  issuing SELECT shard_id, pg_total_relation_size(table_name) FROM (VALUES (981000, 'public.test_table_statistics_hash_981000'), (981001, 'public.test_table_statistics_hash_981001'), (981002, 'public.test_table_statistics_hash_981002'), (981003, 'public.test_table_statistics_hash_981003'), (981004, 'public.test_table_statistics_hash_981004'), (981005, 'public.test_table_statistics_hash_981005'), (981006, 'public.test_table_statistics_hash_981006'), (981007, 'public.test_table_statistics_hash_981007')) t(shard_id, table_name) WHERE to_regclass(table_name) IS NOT NULL
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
 NOTICE:  issuing COMMIT
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
@@ -152,11 +152,11 @@ SET citus.multi_shard_modify_mode TO sequential;
 SELECT citus_update_table_statistics('test_table_statistics_append');
 NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
-NOTICE:  issuing SELECT 981008 AS shard_id, 'public.test_table_statistics_append_981008' AS shard_name, pg_total_relation_size('public.test_table_statistics_append_981008') UNION ALL SELECT 981009 AS shard_id, 'public.test_table_statistics_append_981009' AS shard_name, pg_total_relation_size('public.test_table_statistics_append_981009') UNION ALL SELECT 0::bigint, NULL::text, 0::bigint;
+NOTICE:  issuing SELECT shard_id, pg_total_relation_size(table_name) FROM (VALUES (981008, 'public.test_table_statistics_append_981008'), (981009, 'public.test_table_statistics_append_981009')) t(shard_id, table_name) WHERE to_regclass(table_name) IS NOT NULL
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
 NOTICE:  issuing BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;SELECT assign_distributed_transaction_id(xx, xx, 'xxxxxxx');
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
-NOTICE:  issuing SELECT 981008 AS shard_id, 'public.test_table_statistics_append_981008' AS shard_name, pg_total_relation_size('public.test_table_statistics_append_981008') UNION ALL SELECT 981009 AS shard_id, 'public.test_table_statistics_append_981009' AS shard_name, pg_total_relation_size('public.test_table_statistics_append_981009') UNION ALL SELECT 0::bigint, NULL::text, 0::bigint;
+NOTICE:  issuing SELECT shard_id, pg_total_relation_size(table_name) FROM (VALUES (981008, 'public.test_table_statistics_append_981008'), (981009, 'public.test_table_statistics_append_981009')) t(shard_id, table_name) WHERE to_regclass(table_name) IS NOT NULL
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
 NOTICE:  issuing COMMIT
 DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx

src/test/regress/expected/multi_extension.out

@@ -1330,6 +1330,22 @@ SELECT * FROM multi_extension.print_extension_changes();
                  | view citus_stat_tenants_local
 (11 rows)
 
+-- Test downgrade to 11.3-1 from 11.3-2
+ALTER EXTENSION citus UPDATE TO '11.3-2';
+ALTER EXTENSION citus UPDATE TO '11.3-1';
+-- Should be empty result since upgrade+downgrade should be a no-op
+SELECT * FROM multi_extension.print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
+-- Snapshot of state at 11.3-2
+ALTER EXTENSION citus UPDATE TO '11.3-2';
+SELECT * FROM multi_extension.print_extension_changes();
+ previous_object | current_object
+---------------------------------------------------------------------
+(0 rows)
+
 DROP TABLE multi_extension.prev_objects, multi_extension.extension_diff;
 -- show running version
 SHOW citus.version;

src/test/regress/sql/multi_extension.sql

@@ -591,6 +591,16 @@ SELECT * FROM multi_extension.print_extension_changes();
 ALTER EXTENSION citus UPDATE TO '11.3-1';
 SELECT * FROM multi_extension.print_extension_changes();
 
+-- Test downgrade to 11.3-1 from 11.3-2
+ALTER EXTENSION citus UPDATE TO '11.3-2';
+ALTER EXTENSION citus UPDATE TO '11.3-1';
+-- Should be empty result since upgrade+downgrade should be a no-op
+SELECT * FROM multi_extension.print_extension_changes();
+
+-- Snapshot of state at 11.3-2
+ALTER EXTENSION citus UPDATE TO '11.3-2';
+SELECT * FROM multi_extension.print_extension_changes();
+
 DROP TABLE multi_extension.prev_objects, multi_extension.extension_diff;
 
 -- show running version