Follow-up to MDEV-13563 mariabackup --lock-ddl-per-table

Fix memory leaks, and add a missing newline to a message.

extra/mariabackup/backup_mysql.cc

@@ -1662,6 +1662,7 @@ static void check_mdl_lock_works(const char *table_name)
   int err_no = mysql_errno(test_con);
   DBUG_ASSERT(err_no == ER_STATEMENT_TIMEOUT);
   mysql_close(test_con);
+  free(query);
 }
 #endif
 
@@ -1671,53 +1672,42 @@ dict_fs2utf8(const char*, char*, size_t, char*, size_t);
 void
 mdl_lock_table(ulint space_id)
 {
-  char *query;
+  static const char q[] = "SELECT NAME "
+    "FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES "
+    "WHERE SPACE = " ULINTPF " AND NAME LIKE '%%/%%'";
+  char query[22 + sizeof q];
+  snprintf(query, sizeof query, q, space_id);
 
   pthread_mutex_lock(&mdl_lock_con_mutex);
 
-  xb_a(asprintf(&query,
-    "SELECT NAME FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES "
-    "WHERE SPACE = %llu AND NAME LIKE '%%/%%'", (ulonglong)space_id));
-
-  xb_mysql_query(mdl_con, query, true, true);
-
-  MYSQL_RES *mysql_result = xb_mysql_query(mdl_con, query, true);
-
-  MYSQL_ROW row;
-  while ((row = mysql_fetch_row(mysql_result))) {
+  MYSQL_RES *mysql_result = xb_mysql_query(mdl_con, query, true, true);
+  while (MYSQL_ROW row = mysql_fetch_row(mysql_result)) {
     char full_table_name[2*FN_REFLEN +2];
     char db_utf8[FN_REFLEN];
     char table_utf8[FN_REFLEN];
+    static const char lq[] = "SELECT * FROM %s LIMIT 0";
+    char lock_query[sizeof full_table_name + sizeof lq];
 
-    dict_fs2utf8(row[0], db_utf8, sizeof(db_utf8),table_utf8,sizeof(table_utf8));
+    dict_fs2utf8(row[0], db_utf8, sizeof db_utf8,table_utf8,sizeof table_utf8);
     snprintf(full_table_name,sizeof(full_table_name),"`%s`.`%s`",db_utf8,table_utf8);
-  
-    char *lock_query;
-
     msg_ts("Locking MDL for %s\n", full_table_name);
-
-    xb_a(asprintf(&lock_query,
-    "SELECT * FROM %s LIMIT 0",
-    full_table_name));
+    snprintf(lock_query, sizeof lock_query, lq, full_table_name);
 
     xb_mysql_query(mdl_con, lock_query, false, false);
 
-    free(lock_query);
-
     DBUG_EXECUTE_IF("check_mdl_lock_works",
       check_mdl_lock_works(full_table_name););
   }
 
- mysql_free_result(mysql_result);
- free(query);
- pthread_mutex_unlock(&mdl_lock_con_mutex);
+  pthread_mutex_unlock(&mdl_lock_con_mutex);
+  mysql_free_result(mysql_result);
 }
 
 
 void
 mdl_unlock_all()
 {
-  msg_ts("Unlocking MDL for all tables");
+  msg_ts("Unlocking MDL for all tables\n");
   xb_mysql_query(mdl_con, "COMMIT", false, true);
   mysql_close(mdl_con);
   pthread_mutex_destroy(&mdl_lock_con_mutex);