implement GetOnlyShardOidOfReferenceTable and some refactor in shard_uitls

src/backend/distributed/commands/local_multi_copy.c

@@ -159,7 +159,7 @@ DoLocalCopy(StringInfo buffer, Oid relationId, int64 shardId, CopyStmt *copyStat
 	 */
 	LocalCopyBuffer = buffer;
 
-	Oid shardOid = GetShardLocalTableOid(relationId, shardId);
+	Oid shardOid = GetTableLocalShardOid(relationId, shardId);
 	Relation shard = heap_open(shardOid, RowExclusiveLock);
 	ParseState *pState = make_parsestate(NULL);
 

src/backend/distributed/planner/deparse_shard_query.c

@@ -339,7 +339,7 @@ UpdateRelationsToLocalShardTables(Node *node, List *relationShardList)
 		return true;
 	}
 
-	Oid shardOid = GetShardLocalTableOid(relationShard->relationId,
+	Oid shardOid = GetTableLocalShardOid(relationShard->relationId,
 										 relationShard->shardId);
 
 	newRte->relid = shardOid;

src/backend/distributed/utils/shard_utils.c

@@ -11,21 +11,48 @@
 
 #include "postgres.h"
 #include "utils/lsyscache.h"
-
+#include "distributed/metadata_cache.h"
 #include "distributed/relay_utility.h"
 #include "distributed/shard_utils.h"
 
 /*
- * GetShardLocalTableOid returns the oid of the shard from the given distributed relation
- * with the shardid.
+ * GetTableLocalShardOid returns the oid of the shard from the given distributed
+ * relation with the shardId.
  */
 Oid
-GetShardLocalTableOid(Oid distRelId, uint64 shardId)
+GetTableLocalShardOid(Oid citusTableOid, uint64 shardId)
 {
-	char *relationName = get_rel_name(distRelId);
-	AppendShardIdToName(&relationName, shardId);
+	const char *citusTableName = get_rel_name(citusTableOid);
 
-	Oid schemaId = get_rel_namespace(distRelId);
+	Assert(citusTableName != NULL);
 
-	return get_relname_relid(relationName, schemaId);
+	/* construct shard relation name */
+	char *shardRelationName = pstrdup(citusTableName);
+	AppendShardIdToName(&shardRelationName, shardId);
+
+	Oid citusTableSchemaOid = get_rel_namespace(citusTableOid);
+
+	Oid shardRelationOid = get_relname_relid(shardRelationName, citusTableSchemaOid);
+
+	return shardRelationOid;
+}
+
+
+/*
+ * GetReferenceTableLocalShardOid returns OID of the local shard of given
+ * reference table. Caller of this function must ensure that referenceTableOid
+ * is owned by a reference table.
+ */
+Oid
+GetReferenceTableLocalShardOid(Oid referenceTableOid)
+{
+	const CitusTableCacheEntry *cacheEntry = GetCitusTableCacheEntry(referenceTableOid);
+
+	/* given OID should belong to a valid reference table */
+	Assert(cacheEntry != NULL && cacheEntry->partitionMethod == DISTRIBUTE_BY_NONE);
+
+	const ShardInterval *shardInterval = cacheEntry->sortedShardIntervalArray[0];
+	uint64 referenceTableShardId = shardInterval->shardId;
+
+	return GetTableLocalShardOid(referenceTableOid, referenceTableShardId);
 }

src/include/distributed/shard_utils.h

@@ -13,6 +13,7 @@
 
 #include "postgres.h"
 
-extern Oid GetShardLocalTableOid(Oid distRelId, uint64 shardId);
+extern Oid GetTableLocalShardOid(Oid citusTableOid, uint64 shardId);
+extern Oid GetReferenceTableLocalShardOid(Oid referenceTableOid);
 
 #endif /* SHARD_UTILS_H */