MDEV-28683 Spider: create conn on demand when direct delete

We do this in 10.4 at the same place where in 10.5+ dml_init() is
called which does the same thing, among other things.

Author: mariadb-YuchenPei

storage/spider/ha_spider.cc

@@ -10999,6 +10999,8 @@ int ha_spider::direct_delete_rows_init()
     DBUG_RETURN(bulk_access_link_exec_tgt->spider->direct_delete_rows_init());
   }
 #endif
+  if (int error_num = spider_check_trx_and_get_conn(thd, this, TRUE))
+    DBUG_RETURN(error_num);
   direct_update_init(
     thd,
     FALSE

storage/spider/mysql-test/spider/bugfix/t/mdev_28683.test

@@ -0,0 +1,29 @@
+--echo #
+--echo # MDEV-28683 Spider: SIGSEGV in spider_db_direct_delete, SIGSEGV in spider_db_connect, ASAN: heap-use-after-free in spider_db_direct_delete
+--echo #
+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+CREATE TABLE t (c INT) ENGINE=Spider;
+--error ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+SELECT * FROM t;
+--error 12701
+INSERT INTO t (SELECT 1 FROM t);
+LOCK TABLES t WRITE CONCURRENT;
+--error 12701
+DELETE FROM t;
+
+UNLOCK TABLES;
+DROP TABLE t;
+
+--disable_query_log
+--disable_result_log
+--source ../../t/test_deinit.inc
+--enable_result_log
+--enable_query_log
+--echo #
+--echo # end of test mdev_28683
+--echo #

storage/spider/spd_trx.cc

@@ -3720,9 +3720,6 @@ int spider_check_trx_and_get_conn(
       for (roop_count = 0; roop_count < (int) share->link_count; roop_count++)
       {
         if (
-/*
-          spider->conn_kind[roop_count] != SPIDER_CONN_KIND_MYSQL &&
-*/
           share->hs_dbton_ids[spider->conn_link_idx[roop_count]] ==
             SPIDER_DBTON_SIZE
         ) {