Rename sequence instead of drop

src/backend/distributed/commands/sequence.c

@@ -656,3 +656,45 @@ PostprocessAlterSequenceOwnerStmt(Node *node, const char *queryString)
 
 	return NIL;
 }
+
+
+/*
+ * GenerateBackupNameForSequenceCollision generates a new sequence name for an existing
+ * sequence. The name is generated in such a way that the new name doesn't overlap with
+ * an existing relation by adding a suffix with incrementing number after the new name.
+ */
+char *
+GenerateBackupNameForSequenceCollision(const ObjectAddress *address)
+{
+	char *newName = palloc0(NAMEDATALEN);
+	char suffix[NAMEDATALEN] = { 0 };
+	int count = 0;
+	char *namespaceName = get_namespace_name(get_rel_namespace(address->objectId));
+	Oid schemaId = get_namespace_oid(namespaceName, false);
+
+	char *baseName = get_rel_name(address->objectId);
+	int baseLength = strlen(baseName);
+
+	while (true)
+	{
+		int suffixLength = SafeSnprintf(suffix, NAMEDATALEN - 1, "(citus_backup_%d)",
+										count);
+
+		/* trim the base name at the end to leave space for the suffix and trailing \0 */
+		baseLength = Min(baseLength, NAMEDATALEN - suffixLength - 1);
+
+		/* clear newName before copying the potentially trimmed baseName and suffix */
+		memset(newName, 0, NAMEDATALEN);
+		strncpy_s(newName, NAMEDATALEN, baseName, baseLength);
+		strncpy_s(newName + baseLength, NAMEDATALEN - baseLength, suffix,
+				  suffixLength);
+
+		Oid typeOid = get_relname_relid(newName, schemaId);
+		if (typeOid == InvalidOid)
+		{
+			return newName;
+		}
+
+		count++;
+	}
+}

src/backend/distributed/worker/worker_create_or_replace.c

@@ -33,8 +33,6 @@
 #include "distributed/worker_protocol.h"
 
 static const char * CreateStmtByObjectAddress(const ObjectAddress *address);
-static RenameStmt * CreateRenameStatement(const ObjectAddress *address, char *newName);
-static char * GenerateBackupNameForCollision(const ObjectAddress *address);
 
 PG_FUNCTION_INFO_V1(worker_create_or_replace_object);
 
@@ -166,7 +164,7 @@ CreateStmtByObjectAddress(const ObjectAddress *address)
  * address. This name should be used when renaming an existing object before creating the
  * new object locally on the worker.
  */
-static char *
+char *
 GenerateBackupNameForCollision(const ObjectAddress *address)
 {
 	switch (getObjectClass(address))
@@ -186,6 +184,15 @@ GenerateBackupNameForCollision(const ObjectAddress *address)
 			return GenerateBackupNameForTypeCollision(address);
 		}
 
+		case OCLASS_CLASS:
+		{
+			char relKind = get_rel_relkind(address->objectId);
+			if (relKind == RELKIND_SEQUENCE)
+			{
+				return GenerateBackupNameForSequenceCollision(address);
+			}
+		}
+
 		default:
 		{
 			ereport(ERROR, (errmsg("unsupported object to construct a rename statement"),
@@ -243,6 +250,7 @@ CreateRenameTypeStmt(const ObjectAddress *address, char *newName)
 														  address->objectId));
 	stmt->newname = newName;
 
+
 	return stmt;
 }
 
@@ -265,11 +273,43 @@ CreateRenameProcStmt(const ObjectAddress *address, char *newName)
 }
 
 
+/*
+ * CreateRenameSequenceStmt creates a rename statement for a sequence based on its
+ * ObjectAddress. The rename statement will rename the existing object on its address
+ * to the value provided in newName.
+ */
+static RenameStmt *
+CreateRenameSequenceStmt(const ObjectAddress *address, char *newName)
+{
+	RenameStmt *stmt = makeNode(RenameStmt);
+	Oid seqOid = address->objectId;
+
+	HeapTuple seqClassTuple = SearchSysCache1(RELOID, seqOid);
+	if (!HeapTupleIsValid(seqClassTuple))
+	{
+		ereport(ERROR, (errmsg("citus cache lookup error")));
+	}
+	Form_pg_class seqClassForm = (Form_pg_class) GETSTRUCT(seqClassTuple);
+
+	char *schemaName = get_namespace_name(seqClassForm->relnamespace);
+	char *seqName = NameStr(seqClassForm->relname);
+	List *name = list_make2(makeString(schemaName), makeString(seqName));
+	ReleaseSysCache(seqClassTuple);
+
+	stmt->renameType = OBJECT_SEQUENCE;
+	stmt->object = (Node *) name;
+	stmt->relation = makeRangeVar(schemaName, seqName, -1);
+	stmt->newname = newName;
+
+	return stmt;
+}
+
+
 /*
  * CreateRenameStatement creates a rename statement for an existing object to rename the
  * object to newName.
  */
-static RenameStmt *
+RenameStmt *
 CreateRenameStatement(const ObjectAddress *address, char *newName)
 {
 	switch (getObjectClass(address))
@@ -289,6 +329,15 @@ CreateRenameStatement(const ObjectAddress *address, char *newName)
 			return CreateRenameTypeStmt(address, newName);
 		}
 
+		case OCLASS_CLASS:
+		{
+			char relKind = get_rel_relkind(address->objectId);
+			if (relKind == RELKIND_SEQUENCE)
+			{
+				return CreateRenameSequenceStmt(address, newName);
+			}
+		}
+
 		default:
 		{
 			ereport(ERROR, (errmsg("unsupported object to construct a rename statement"),

src/backend/distributed/worker/worker_data_fetch_protocol.c

@@ -32,6 +32,7 @@
 #include "distributed/commands/utility_hook.h"
 #include "distributed/connection_management.h"
 #include "distributed/coordinator_protocol.h"
+#include "distributed/deparser.h"
 #include "distributed/intermediate_results.h"
 #include "distributed/listutils.h"
 #include "distributed/metadata_cache.h"
@@ -44,6 +45,7 @@
 #include "distributed/remote_commands.h"
 #include "distributed/resource_lock.h"
 
+#include "distributed/worker_create_or_replace.h"
 #include "distributed/worker_protocol.h"
 #include "distributed/version_compat.h"
 #include "executor/spi.h"
@@ -480,13 +482,16 @@ worker_apply_sequence_command(PG_FUNCTION_ARGS)
 		Form_pg_sequence pgSequenceForm = pg_get_sequencedef(sequenceOid);
 		if (pgSequenceForm->seqtypid != sequenceTypeId)
 		{
-			StringInfo dropSequenceString = makeStringInfo();
+			ObjectAddress sequenceAddress = { 0 };
-			char *qualifiedSequenceName = quote_qualified_identifier(sequenceSchema,
+			ObjectAddressSet(sequenceAddress, RelationRelationId, sequenceOid);
-																	 sequenceName);
+
-			appendStringInfoString(dropSequenceString, "DROP SEQUENCE ");
+			char *newName = GenerateBackupNameForCollision(&sequenceAddress);
-			appendStringInfoString(dropSequenceString, qualifiedSequenceName);
+
-			appendStringInfoString(dropSequenceString, ";");
+			RenameStmt *renameStmt = CreateRenameStatement(&sequenceAddress, newName);
-			ExecuteQueryViaSPI(dropSequenceString->data, SPI_OK_UTILITY);
+			const char *sqlRenameStmt = DeparseTreeNode((Node *) renameStmt);
+			ProcessUtilityParseTree((Node *) renameStmt, sqlRenameStmt,
+									PROCESS_UTILITY_QUERY,
+									NULL, None_Receiver, NULL);
 		}
 	}
 
@@ -495,8 +500,8 @@ worker_apply_sequence_command(PG_FUNCTION_ARGS)
 							None_Receiver, NULL);
 	CommandCounterIncrement();
 
-	sequenceRelationId = RangeVarGetRelid(createSequenceStatement->sequence,
+	Oid sequenceRelationId = RangeVarGetRelid(createSequenceStatement->sequence,
-										  AccessShareLock, false);
+											  AccessShareLock, false);
 	Assert(sequenceRelationId != InvalidOid);
 
 	AlterSequenceMinMax(sequenceRelationId, sequenceSchema, sequenceName, sequenceTypeId);

src/include/distributed/commands.h

@@ -397,6 +397,7 @@ extern ObjectAddress AlterSequenceOwnerStmtObjectAddress(Node *node, bool missin
 extern ObjectAddress RenameSequenceStmtObjectAddress(Node *node, bool missing_ok);
 extern void ErrorIfUnsupportedSeqStmt(CreateSeqStmt *createSeqStmt);
 extern void ErrorIfDistributedAlterSeqOwnedBy(AlterSeqStmt *alterSeqStmt);
+extern char * GenerateBackupNameForSequenceCollision(const ObjectAddress *address);
 
 /* statistics.c - forward declarations */
 extern List * PreprocessCreateStatisticsStmt(Node *node, const char *queryString,

src/include/distributed/worker_create_or_replace.h

@@ -14,8 +14,12 @@
 #ifndef WORKER_CREATE_OR_REPLACE_H
 #define WORKER_CREATE_OR_REPLACE_H
 
+#include "catalog/objectaddress.h"
+
 #define CREATE_OR_REPLACE_COMMAND "SELECT worker_create_or_replace_object(%s);"
 
 extern char * WrapCreateOrReplace(const char *sql);
+extern char * GenerateBackupNameForCollision(const ObjectAddress *address);
+extern RenameStmt * CreateRenameStatement(const ObjectAddress *address, char *newName);
 
 #endif /* WORKER_CREATE_OR_REPLACE_H */