1 files changed, 55 insertions, 1 deletions

diff --git a/src/bin/pg_upgrade/info.c b/src/bin/pg_upgrade/info.c
index 4878aa22bfd..f70742851c4 100644
--- a/src/bin/pg_upgrade/info.c
+++ b/src/bin/pg_upgrade/info.c
@@ -28,6 +28,7 @@ static void print_db_infos(DbInfoArr *db_arr);
 static void print_rel_infos(RelInfoArr *rel_arr);
 static void print_slot_infos(LogicalSlotInfoArr *slot_arr);
 static void get_old_cluster_logical_slot_infos(DbInfo *dbinfo, bool live_check);
+static void get_db_subscription_count(DbInfo *dbinfo);
 
 
 /*
@@ -293,10 +294,14 @@ get_db_rel_and_slot_infos(ClusterInfo *cluster, bool live_check)
 		get_rel_infos(cluster, pDbInfo);
 
 		/*
-		 * Retrieve the logical replication slots infos for the old cluster.
+		 * Retrieve the logical replication slots infos and the subscriptions
+		 * count for the old cluster.
 		 */
 		if (cluster == &old_cluster)
+		{
 			get_old_cluster_logical_slot_infos(pDbInfo, live_check);
+			get_db_subscription_count(pDbInfo);
+		}
 	}
 
 	if (cluster == &old_cluster)
@@ -730,6 +735,55 @@ count_old_cluster_logical_slots(void)
 	return slot_count;
 }
 
+/*
+ * get_db_subscription_count()
+ *
+ * Gets the number of subscriptions in the database referred to by "dbinfo".
+ *
+ * Note: This function will not do anything if the old cluster is pre-PG17.
+ * This is because before that the logical slots are not upgraded, so we will
+ * not be able to upgrade the logical replication clusters completely.
+ */
+static void
+get_db_subscription_count(DbInfo *dbinfo)
+{
+	PGconn	   *conn;
+	PGresult   *res;
+
+	/* Subscriptions can be migrated since PG17. */
+	if (GET_MAJOR_VERSION(old_cluster.major_version) < 1700)
+		return;
+
+	conn = connectToServer(&old_cluster, dbinfo->db_name);
+	res = executeQueryOrDie(conn, "SELECT count(*) "
+							"FROM pg_catalog.pg_subscription WHERE subdbid = %d",
+							dbinfo->db_oid);
+	dbinfo->nsubs = atoi(PQgetvalue(res, 0, 0));
+
+	PQclear(res);
+	PQfinish(conn);
+}
+
+/*
+ * count_old_cluster_subscriptions()
+ *
+ * Returns the number of subscriptions for all databases.
+ *
+ * Note: this function always returns 0 if the old_cluster is PG16 and prior
+ * because we gather subscriptions only for cluster versions greater than or
+ * equal to PG17. See get_db_subscription_count().
+ */
+int
+count_old_cluster_subscriptions(void)
+{
+	int			nsubs = 0;
+
+	for (int dbnum = 0; dbnum < old_cluster.dbarr.ndbs; dbnum++)
+		nsubs += old_cluster.dbarr.dbs[dbnum].nsubs;
+
+	return nsubs;
+}
+
 static void
 free_db_and_rel_infos(DbInfoArr *db_arr)
 {