Remove pg_dist_shard.shardalias, LoadShardAlias, and all usage of these.

Draft of migration script to drop the column. Removed regression test
of non-null shardalias.

src/backend/distributed/citus--5.2-1--5.3-0.sql

@@ -0,0 +1,5 @@
+/* citus--5.2-1--5.3-0.sql */
+
+ALTER TABLE pg_catalog.pg_dist_shard
+DROP COLUMN IF EXISTS shardalias;
+

src/backend/distributed/citus.sql

@@ -42,7 +42,6 @@ CREATE TABLE citus.pg_dist_shard(
     logicalrelid oid NOT NULL,
     shardid int8 NOT NULL,
     shardstorage "char" NOT NULL,
-    shardalias text,
     shardminvalue text,
     shardmaxvalue text
 );

src/backend/distributed/master/master_delete_protocol.c

@@ -325,18 +325,9 @@ DropShards(Oid relationId, char *schemaName, char *relationName,
 
 		Assert(shardInterval->relationId == relationId);
 
-		/* if shard doesn't have an alias, extend regular table name */
-		shardAlias = LoadShardAlias(relationId, shardId);
-		if (shardAlias == NULL)
-		{
+		/* Build shard relation name. */
 		appendStringInfoString(shardName, relationName);
 		AppendShardIdToStringInfo(shardName, shardId);
-		}
-		else
-		{
-			appendStringInfoString(shardName, shardAlias);
-		}
-
 		quotedShardName = quote_qualified_identifier(schemaName, shardName->data);
 
 		shardPlacementList = ShardPlacementList(shardId);

src/backend/distributed/master/master_metadata_utility.c

@@ -138,72 +138,6 @@ AllocateUint64(uint64 value)
 }
 
 
-/*
- * LoadShardAlias finds the row for given relation and shardId in pg_dist_shard,
- * finds the shard alias in this row if any, and then deep copies this alias.
- */
-char *
-LoadShardAlias(Oid relationId, uint64 shardId)
-{
-	SysScanDesc scanDescriptor = NULL;
-	ScanKeyData scanKey[1];
-	int scanKeyCount = 1;
-	HeapTuple heapTuple = NULL;
-	Datum shardAliasDatum = 0;
-	bool shardAliasNull = false;
-	char *shardAlias = NULL;
-
-	Relation pgDistShard = heap_open(DistShardRelationId(), AccessShareLock);
-	TupleDesc tupleDescriptor = RelationGetDescr(pgDistShard);
-
-	ScanKeyInit(&scanKey[0], Anum_pg_dist_shard_shardid,
-				BTEqualStrategyNumber, F_INT8EQ, Int64GetDatum(shardId));
-
-	scanDescriptor = systable_beginscan(pgDistShard,
-										DistShardShardidIndexId(), true,
-										NULL, scanKeyCount, scanKey);
-
-	/*
-	 * Normally, we should have at most one tuple here as we have a unique index
-	 * on shardId. However, if users want to drop this uniqueness constraint,
-	 * and look up the shardalias based on the relation and shardId pair, we
-	 * still allow that. We don't have any users relaying on this feature. Thus,
-	 * we may consider to remove this check.
-	 */
-	heapTuple = systable_getnext(scanDescriptor);
-	while (HeapTupleIsValid(heapTuple))
-	{
-		Form_pg_dist_shard pgDistShardForm = (Form_pg_dist_shard) GETSTRUCT(heapTuple);
-		if (pgDistShardForm->logicalrelid == relationId)
-		{
-			break;
-		}
-
-		heapTuple = systable_getnext(scanDescriptor);
-	}
-
-	/* if no tuple found, error out */
-	if (!HeapTupleIsValid(heapTuple))
-	{
-		ereport(ERROR, (errmsg("could not find valid entry for relationId: %u "
-							   "and shard " UINT64_FORMAT, relationId, shardId)));
-	}
-
-	/* if shard alias exists, deep copy cstring */
-	shardAliasDatum = heap_getattr(heapTuple, Anum_pg_dist_shard_shardalias,
-								   tupleDescriptor, &shardAliasNull);
-	if (!shardAliasNull)
-	{
-		shardAlias = TextDatumGetCString(shardAliasDatum);
-	}
-
-	systable_endscan(scanDescriptor);
-	heap_close(pgDistShard, AccessShareLock);
-
-	return shardAlias;
-}
-
-
 /*
  * CopyShardInterval copies fields from the specified source ShardInterval
  * into the fields of the provided destination ShardInterval.
@@ -405,15 +339,11 @@ InsertShardRow(Oid relationId, uint64 shardId, char storageType,
 	{
 		values[Anum_pg_dist_shard_shardminvalue - 1] = PointerGetDatum(shardMinValue);
 		values[Anum_pg_dist_shard_shardmaxvalue - 1] = PointerGetDatum(shardMaxValue);
-
-		/* we always set shard alias to null */
-		isNulls[Anum_pg_dist_shard_shardalias - 1] = true;
 	}
 	else
 	{
 		isNulls[Anum_pg_dist_shard_shardminvalue - 1] = true;
 		isNulls[Anum_pg_dist_shard_shardmaxvalue - 1] = true;
-		isNulls[Anum_pg_dist_shard_shardalias - 1] = true;
 	}
 
 	/* open shard relation and insert new tuple */

src/backend/distributed/master/master_stage_protocol.c

@@ -238,13 +238,9 @@ master_append_table_to_shard(PG_FUNCTION_ARGS)
 	shardSchemaOid = get_rel_namespace(relationId);
 	shardSchemaName = get_namespace_name(shardSchemaOid);
 
-	/* if shard doesn't have an alias, extend regular table name */
-	shardTableName = LoadShardAlias(relationId, shardId);
-	if (shardTableName == NULL)
-	{
+	/* Build shard table name. */
 	shardTableName = get_rel_name(relationId);
 	AppendShardIdToName(&shardTableName, shardId);
-	}
 
 	shardQualifiedName = quote_qualified_identifier(shardSchemaName, shardTableName);
 
@@ -493,10 +489,7 @@ UpdateShardStatistics(int64 shardId)
 	text *minValue = NULL;
 	text *maxValue = NULL;
 
-	/* if shard doesn't have an alias, extend regular table name */
-	shardQualifiedName = LoadShardAlias(relationId, shardId);
-	if (shardQualifiedName == NULL)
-	{
+	/* Build shard qualified name. */
 	char *shardName = get_rel_name(relationId);
 
 	Oid schemaId = get_rel_namespace(relationId);
@@ -505,7 +498,6 @@ UpdateShardStatistics(int64 shardId)
 	AppendShardIdToName(&shardName, shardId);
 
 	shardQualifiedName = quote_qualified_identifier(schemaName, shardName);
-	}
 
 	shardPlacementList = FinalizedShardPlacementList(shardId);
 

src/backend/distributed/planner/multi_physical_planner.c

@@ -3753,19 +3753,6 @@ ShardFetchQueryString(uint64 shardId)
 	char *shardSchemaName = NULL;
 	char *shardTableName = NULL;
 
-	/*
-	 * If user specified a shard alias in pg_dist_shard, error out and display a
-	 * message explaining the limitation.
-	 */
-	char *shardAliasName = LoadShardAlias(shardInterval->relationId, shardId);
-	if (shardAliasName != NULL)
-	{
-		ereport(ERROR, (errmsg("cannot fetch shard " UINT64_FORMAT, shardId),
-						errdetail("Fetching shards with aliases is currently "
-								  "unsupported")));
-	}
-	else
-	{
 	/* construct the shard name */
 	Oid shardSchemaId = get_rel_namespace(shardInterval->relationId);
 	char *tableName = get_rel_name(shardInterval->relationId);
@@ -3773,7 +3760,6 @@ ShardFetchQueryString(uint64 shardId)
 	shardSchemaName = get_namespace_name(shardSchemaId);
 	shardTableName = pstrdup(tableName);
 	AppendShardIdToName(&shardTableName, shardId);
-	}
 
 	shardFetchQuery = makeStringInfo();
 	if (storageType == SHARD_STORAGE_TABLE || storageType == SHARD_STORAGE_RELAY ||
@@ -3986,22 +3972,12 @@ FragmentAlias(RangeTblEntry *rangeTableEntry, RangeTableFragment *fragment)
 		aliasName = relationName;
 
 		/*
-		 * If user specified a shard name in pg_dist_shard, use that name in alias.
-		 * Otherwise, set shard name in alias to <relation_name>_<shard_id>.
+		 * Set shard name in alias to <relation_name>_<shard_id>.
 		 */
-		shardAliasName = LoadShardAlias(relationId, shardId);
-		if (shardAliasName != NULL)
-		{
-			fragmentName = shardAliasName;
-		}
-		else
-		{
 		char *shardName = pstrdup(relationName);
 		AppendShardIdToName(&shardName, shardId);
-
 		fragmentName = shardName;
 	}
-	}
 	else if (fragmentType == CITUS_RTE_REMOTE_QUERY)
 	{
 		Task *mergeTask = (Task *) fragment->fragmentReference;

src/include/distributed/master_metadata_utility.h

@@ -59,7 +59,6 @@ typedef struct ShardPlacement
 extern List * LoadShardIntervalList(Oid relationId);
 extern int ShardIntervalCount(Oid relationId);
 extern List * LoadShardList(Oid relationId);
-extern char * LoadShardAlias(Oid relationId, uint64 shardId);
 extern void CopyShardInterval(ShardInterval *srcInterval, ShardInterval *destInterval);
 extern uint64 ShardLength(uint64 shardId);
 extern List * FinalizedShardPlacementList(uint64 shardId);

src/include/distributed/pg_dist_shard.h

@@ -26,7 +26,6 @@ typedef struct FormData_pg_dist_shard
 	int64 shardid;            /* global shardId representing remote partition */
 	char shardstorage;        /* shard storage type; see codes below */
 #ifdef CATALOG_VARLEN           /* variable-length fields start here */
-	text shardalias;           /* user specified table name for shard, if any */
 	text shardminvalue;        /* partition key's minimum value in shard */
 	text shardmaxvalue;        /* partition key's maximum value in shard */
 #endif
@@ -43,13 +42,12 @@ typedef FormData_pg_dist_shard *Form_pg_dist_shard;
  *      compiler constants for pg_dist_shards
  * ----------------
  */
-#define Natts_pg_dist_shard 6
+#define Natts_pg_dist_shard 5
 #define Anum_pg_dist_shard_logicalrelid 1
 #define Anum_pg_dist_shard_shardid 2
 #define Anum_pg_dist_shard_shardstorage 3
-#define Anum_pg_dist_shard_shardalias 4
-#define Anum_pg_dist_shard_shardminvalue 5
-#define Anum_pg_dist_shard_shardmaxvalue 6
+#define Anum_pg_dist_shard_shardminvalue 4
+#define Anum_pg_dist_shard_shardmaxvalue 5
 
 /*
  * Valid values for shard storage types include relay file, foreign table,

src/test/regress/.gitignore

@@ -5,3 +5,5 @@
 /tmp_check/
 /results/
 /log/
+/regression.out
+/regression.diffs

src/test/regress/expected/multi_table_ddl.out

@@ -53,8 +53,8 @@ SELECT * FROM pg_dist_partition;
 (0 rows)
 
 SELECT * FROM pg_dist_shard;
- logicalrelid | shardid | shardstorage | shardalias | shardminvalue | shardmaxvalue 
---------------+---------+--------------+------------+---------------+---------------
+ logicalrelid | shardid | shardstorage | shardminvalue | shardmaxvalue 
+--------------+---------+--------------+---------------+---------------
 (0 rows)
 
 SELECT * FROM pg_dist_shard_placement;

src/test/regress/expected/multi_verify_no_join_with_alias.out

@@ -1,22 +0,0 @@
---
--- MULTI_VERIFY_NO_JOIN_WITH_ALIAS
---
--- This test checks that we simply emit an error message instead of trying to
--- fetch and join a shard which has an alias set.
-ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 1020000;
-ALTER SEQUENCE pg_catalog.pg_dist_jobid_seq RESTART 1020000;
--- Show that the join works without an alias
-SELECT COUNT(*) FROM lineitem, part WHERE l_partkey = p_partkey;
- count 
--------
-    61
-(1 row)
-
--- Assign an alias to the parts shard
-UPDATE pg_dist_shard SET shardalias = 'my_alias' WHERE shardid = 290000;
--- Attempt a join which uses this shard
-SELECT COUNT(*) FROM lineitem, part WHERE l_partkey = p_partkey;
-ERROR:  cannot fetch shard 290000
-DETAIL:  Fetching shards with aliases is currently unsupported
--- Remove the alias from the parts shard
-UPDATE pg_dist_shard SET shardalias = NULL WHERE shardid = 290000;

src/test/regress/multi_schedule

@@ -44,7 +44,6 @@ test: multi_query_directory_cleanup
 test: multi_task_assignment_policy
 test: multi_utility_statements
 test: multi_dropped_column_aliases
-test: multi_verify_no_join_with_alias
 test: multi_binary_master_copy_format
 test: multi_prepare_sql multi_prepare_plsql
 

src/test/regress/multi_task_tracker_extra_schedule

@@ -39,7 +39,6 @@ test: multi_query_directory_cleanup
 test: multi_task_assignment_policy
 test: multi_utility_statements
 test: multi_dropped_column_aliases
-test: multi_verify_no_join_with_alias
 
 # ----------
 # Parallel TPC-H tests to check our distributed execution behavior

src/test/regress/sql/multi_verify_no_join_with_alias.sql

@@ -1,27 +0,0 @@
---
--- MULTI_VERIFY_NO_JOIN_WITH_ALIAS
---
-
--- This test checks that we simply emit an error message instead of trying to
--- fetch and join a shard which has an alias set.
-
-
-ALTER SEQUENCE pg_catalog.pg_dist_shardid_seq RESTART 1020000;
-ALTER SEQUENCE pg_catalog.pg_dist_jobid_seq RESTART 1020000;
-
-
--- Show that the join works without an alias
-
-SELECT COUNT(*) FROM lineitem, part WHERE l_partkey = p_partkey;
-
--- Assign an alias to the parts shard
-
-UPDATE pg_dist_shard SET shardalias = 'my_alias' WHERE shardid = 290000;
-
--- Attempt a join which uses this shard
-
-SELECT COUNT(*) FROM lineitem, part WHERE l_partkey = p_partkey;
-
--- Remove the alias from the parts shard
-
-UPDATE pg_dist_shard SET shardalias = NULL WHERE shardid = 290000;