Fix bug: alter database shouldn't propagate for undistributed database (#7777)

Before this fix, the following would happen for a database that is not
distributed:

```sql
CREATE DATABASE db_to_test;
NOTICE:  Citus partially supports CREATE DATABASE for distributed databases
DETAIL:  Citus does not propagate CREATE DATABASE command to workers
HINT:  You can manually create a database and its extensions on workers.

ALTER DATABASE db_to_test with CONNECTION LIMIT 100;
NOTICE:  issuing ALTER DATABASE db_to_test WITH  CONNECTION LIMIT 100;
DETAIL:  on server postgres@localhost:57638 connectionId: 2
NOTICE:  issuing ALTER DATABASE db_to_test WITH  CONNECTION LIMIT 100;
DETAIL:  on server postgres@localhost:57637 connectionId: 1
ERROR:  database "db_to_test" does not exist
```

With this fix, we also take care of
https://github.com/citusdata/citus/issues/7763

Fixes #7763

src/backend/distributed/commands/database.c

@@ -24,6 +24,7 @@
 #include "distributed/commands.h"
 #include "distributed/commands/utility_hook.h"
 #include "distributed/deparser.h"
+#include "distributed/metadata/distobject.h"
 #include "distributed/metadata_sync.h"
 #include "distributed/metadata_utility.h"
 #include "distributed/multi_executor.h"
@@ -32,6 +33,8 @@
 
 static AlterOwnerStmt * RecreateAlterDatabaseOwnerStmt(Oid databaseOid);
 static Oid get_database_owner(Oid db_oid);
+static ObjectAddress * GetDatabaseAddressFromDatabaseName(char *databaseName,
+														  bool missingOk);
 List * PreprocessGrantOnDatabaseStmt(Node *node, const char *queryString,
 									 ProcessUtilityContext processUtilityContext);
 
@@ -161,13 +164,15 @@ List *
 PreprocessAlterDatabaseStmt(Node *node, const char *queryString,
 							ProcessUtilityContext processUtilityContext)
 {
-	if (!ShouldPropagate())
+	AlterDatabaseStmt *stmt = castNode(AlterDatabaseStmt, node);
+	bool missingOk = false;
+	ObjectAddress *dbAddress = GetDatabaseAddressFromDatabaseName(stmt->dbname,
+																  missingOk);
+	if (!ShouldPropagate() || !IsAnyObjectDistributed(list_make1(dbAddress)))
 	{
 		return NIL;
 	}
 
-	AlterDatabaseStmt *stmt = castNode(AlterDatabaseStmt, node);
-
 	EnsureCoordinator();
 
 	char *sql = DeparseTreeNode((Node *) stmt);
@@ -213,3 +218,17 @@ PreprocessAlterDatabaseRefreshCollStmt(Node *node, const char *queryString,
 
 
 #endif
+
+
+/*
+ * GetDatabaseAddressFromDatabaseName gets the database name and returns the ObjectAddress
+ * of the database.
+ */
+static ObjectAddress *
+GetDatabaseAddressFromDatabaseName(char *databaseName, bool missingOk)
+{
+	Oid databaseOid = get_database_oid(databaseName, missingOk);
+	ObjectAddress *dbObjectAddress = palloc0(sizeof(ObjectAddress));
+	ObjectAddressSet(*dbObjectAddress, DatabaseRelationId, databaseOid);
+	return dbObjectAddress;
+}

src/test/regress/expected/alter_database_propagation.out

@@ -33,4 +33,11 @@ DETAIL:  on server postgres@localhost:xxxxx connectionId: xxxxxxx
 -- this statement will get error since we don't have a multiple database support for now
 alter database regression rename to regression2;
 ERROR:  current database cannot be renamed
+-- this database is not distributed so we will not see any remote commands
+CREATE DATABASE db_to_test;
+NOTICE:  Citus partially supports CREATE DATABASE for distributed databases
+DETAIL:  Citus does not propagate CREATE DATABASE command to workers
+HINT:  You can manually create a database and its extensions on workers.
+alter database db_to_test with CONNECTION LIMIT 100;
+DROP DATABASE db_to_test;
 set citus.log_remote_commands = false;

src/test/regress/sql/alter_database_propagation.sql

@@ -15,4 +15,9 @@ alter database regression with IS_TEMPLATE false;
 -- this statement will get error since we don't have a multiple database support for now
 alter database regression rename to regression2;
 
+-- this database is not distributed so we will not see any remote commands
+CREATE DATABASE db_to_test;
+alter database db_to_test with CONNECTION LIMIT 100;
+DROP DATABASE db_to_test;
+
 set citus.log_remote_commands = false;