MDEV-26582 SIGSEGV in spider_db_bulk_insert and spider_db_connect and spider_db_before_query, and hang in "End of update loop" / "Reset for next command" query states

Spider accesses a freed connection in ha_spider::end_bulk_insert()
and results in SIGSEGV.

The cause of the bug is that ha_spider::is_bulk_insert_exec_period()
wrongly returns TRUE when the bulk insertion has not yet started.

Spider decides whether it is during the bulk insertion or not by
the value of insert_pos, but the variable is not reset in a case,
and this result in the bug.

storage/spider/mysql-test/spider/bugfix/r/mdev_26582.result

@@ -0,0 +1,11 @@
+#
+# MDEV-26582 SIGSEGV in spider_db_bulk_insert and spider_db_connect and spider_db_before_query, and hang in "End of update loop" / "Reset for next command" query states
+#
+CREATE DATABASE IF NOT EXISTS auto_test_local;
+USE auto_test_local;
+CREATE TABLE t (i CHAR) ENGINE=SPIDER;
+INSERT INTO t VALUES (0);
+ERROR HY000: Unable to connect to foreign data source: localhost
+INSERT t SELECT 1 ON DUPLICATE KEY UPDATE c=1;
+ERROR 42S22: Unknown column 'c' in 'field list'
+DROP DATABASE IF EXISTS auto_test_local;

storage/spider/mysql-test/spider/bugfix/t/mdev_26582.cnf

@@ -0,0 +1,2 @@
+!include include/default_mysqld.cnf
+!include ../my_1_1.cnf

storage/spider/mysql-test/spider/bugfix/t/mdev_26582.test

@@ -0,0 +1,27 @@
+--echo #
+--echo # MDEV-26582 SIGSEGV in spider_db_bulk_insert and spider_db_connect and spider_db_before_query, and hang in "End of update loop" / "Reset for next command" query states
+--echo #
+
+# NOTE: The bug does not reproduce if we import ../../t/test_init.inc instead.
+--disable_query_log
+--disable_result_log
+--source ../../include/init_spider.inc
+--enable_result_log
+--enable_query_log
+
+CREATE DATABASE IF NOT EXISTS auto_test_local;
+USE auto_test_local;
+
+CREATE TABLE t (i CHAR) ENGINE=SPIDER;
+--error ER_CONNECT_TO_FOREIGN_DATA_SOURCE
+INSERT INTO t VALUES (0);
+--error ER_BAD_FIELD_ERROR
+INSERT t SELECT 1 ON DUPLICATE KEY UPDATE c=1;
+
+DROP DATABASE IF EXISTS auto_test_local;
+
+--disable_query_log
+--disable_result_log
+--source ../../include/deinit_spider.inc
+--enable_result_log
+--enable_query_log

storage/spider/spd_db_conn.cc

@@ -6661,7 +6661,11 @@ int spider_db_bulk_insert(
 #endif
       if ((error_num = spider->append_insert_values_sql_part(
         SPIDER_SQL_TYPE_INSERT_SQL)))
+      {
+        if (spider->sql_kinds & SPIDER_SQL_KIND_SQL)
+          spider->set_insert_to_pos_sql(SPIDER_SQL_TYPE_INSERT_SQL);
         DBUG_RETURN(error_num);
+      }
 #if defined(HS_HAS_SQLCOM) && defined(HAVE_HANDLERSOCKET)
     }
     if (spider->sql_kinds & SPIDER_SQL_KIND_HS)
@@ -6681,6 +6685,8 @@ int spider_db_bulk_insert(
     if ((error_num = spider->append_insert_terminator_sql_part(
       SPIDER_SQL_TYPE_INSERT_SQL)))
     {
+      if (spider->sql_kinds & SPIDER_SQL_KIND_SQL)
+        spider->set_insert_to_pos_sql(SPIDER_SQL_TYPE_INSERT_SQL);
       DBUG_RETURN(error_num);
     }
 #ifdef HA_CAN_BULK_ACCESS
@@ -6715,6 +6721,8 @@ int spider_db_bulk_insert(
           if ((error_num = dbton_handler->set_sql_for_exec(sql_type,
             roop_count2)))
           {
+            if (spider->sql_kinds & SPIDER_SQL_KIND_SQL)
+              spider->set_insert_to_pos_sql(SPIDER_SQL_TYPE_INSERT_SQL);
             if (dbton_handler->need_lock_before_set_sql_for_exec(sql_type))
             {
               SPIDER_CLEAR_FILE_POS(&conn->mta_conn_mutex_file_pos);
@@ -6744,6 +6752,8 @@ int spider_db_bulk_insert(
         conn->mta_conn_mutex_unlock_later = TRUE;
         if ((error_num = spider_db_set_names(spider, conn, roop_count2)))
         {
+          if (spider->sql_kinds & SPIDER_SQL_KIND_SQL)
+            spider->set_insert_to_pos_sql(SPIDER_SQL_TYPE_INSERT_SQL);
           DBUG_ASSERT(conn->mta_conn_mutex_lock_already);
           DBUG_ASSERT(conn->mta_conn_mutex_unlock_later);
           conn->mta_conn_mutex_lock_already = FALSE;