MDEV-31996 Create connection on demand in spider_db_delete_all_rows

When spider_db_delete_all_rows() is called, the supplied spider->conns
may have already been freed. The existing mechanism has spider_trx own
the connections in trx_conn_hash and it may free a conn during the
cleanup after a query. When running a delete query and if the table is
in the table cache, ha_spider::open() would not be called which would
recreate the conn. So we recreate the conn when necessary during
delete by calling spider_check_trx_and_get_conn().

We also reduce code duplication as delete_all_rows() and truncate()
has almost identical code, and there's no need to assign
wide_handler->sql_command in these functions because it has already
been correctly assigned.

storage/spider/ha_spider.cc

@@ -11223,41 +11223,11 @@ int ha_spider::pre_direct_delete_rows()
 
 int ha_spider::delete_all_rows()
 {
-  int error_num, roop_count;
   THD *thd = ha_thd();
-  backup_error_status();
   DBUG_ENTER("ha_spider::delete_all_rows");
-  DBUG_PRINT("info",("spider this=%p", this));
   if (spider_param_delete_all_rows_type(thd, share->delete_all_rows_type))
     DBUG_RETURN(HA_ERR_WRONG_COMMAND);
-  if (spider_param_read_only_mode(thd, share->read_only_mode))
-  {
-    my_printf_error(ER_SPIDER_READ_ONLY_NUM, ER_SPIDER_READ_ONLY_STR, MYF(0),
-      table_share->db.str, table_share->table_name.str);
-    DBUG_RETURN(ER_SPIDER_READ_ONLY_NUM);
-  }
-#ifdef HANDLER_HAS_DIRECT_UPDATE_ROWS
-  do_direct_update = FALSE;
-#endif
-  sql_kinds = SPIDER_SQL_KIND_SQL;
-  for (roop_count = 0; roop_count < (int) share->link_count; roop_count++)
-    sql_kind[roop_count] = SPIDER_SQL_KIND_SQL;
-  if ((error_num = spider_db_delete_all_rows(this)))
-    DBUG_RETURN(check_error_mode(error_num));
-  if (sql_command == SQLCOM_TRUNCATE && table->found_next_number_field)
-  {
-    DBUG_PRINT("info",("spider reset auto increment"));
-    pthread_mutex_lock(&share->lgtm_tblhnd_share->auto_increment_mutex);
-    share->lgtm_tblhnd_share->auto_increment_lclval = 1;
-    share->lgtm_tblhnd_share->auto_increment_init = FALSE;
-    share->lgtm_tblhnd_share->auto_increment_value = 1;
-    DBUG_PRINT("info",("spider init auto_increment_lclval=%llu",
-      share->lgtm_tblhnd_share->auto_increment_lclval));
-    DBUG_PRINT("info",("spider auto_increment_value=%llu",
-      share->lgtm_tblhnd_share->auto_increment_value));
-    pthread_mutex_unlock(&share->lgtm_tblhnd_share->auto_increment_mutex);
-  }
-  DBUG_RETURN(0);
+  DBUG_RETURN(truncate());
 }
 
 int ha_spider::truncate()

storage/spider/mysql-test/spider/bugfix/r/mdev_31996.result

+for master_1
+for child2
+for child3
+CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+set session spider_delete_all_rows_type=0;
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+delete from t1;
+drop table t1, t2;
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+insert ignore into t1 values (42), (378);
+select * from t1;
+c
+42
+378
+delete from t1;
+select * from t1;
+c
+drop table t1, t2;
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+truncate t1;
+drop table t1, t2;
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+insert ignore into t1 values (42), (378);
+select * from t1;
+c
+42
+378
+truncate t1;
+select * from t1;
+c
+drop table t1, t2;
+drop server srv;
+for master_1
+for child2
+for child3
+#
+# end of test tmp
+#

storage/spider/mysql-test/spider/bugfix/t/mdev_31996.test

+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+
+evalp CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+
+set session spider_delete_all_rows_type=0;
+
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+delete from t1;
+drop table t1, t2;
+
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+insert ignore into t1 values (42), (378);
+select * from t1;
+delete from t1;
+select * from t1;
+drop table t1, t2;
+
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+truncate t1;
+drop table t1, t2;
+
+create table t2 (c int);
+create table t1 (c int) ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2", delete_all_rows_type "0"';
+insert ignore into t1 values (42), (378);
+select * from t1;
+truncate t1;
+select * from t1;
+drop table t1, t2;
+
+drop server srv;
+--disable_query_log
+--disable_result_log
+--source ../../t/test_deinit.inc
+--enable_result_log
+--enable_query_log
+--echo #
+--echo # end of test tmp
+--echo #