Bug#11829785 EXPLAIN EXTENDED CRASH WITH RIGHT OUTER JOIN, SUBQUERIES

This is a backport of
Bug #46860 Crash/segfault using EXPLAIN EXTENDED on query using UNION in subquery.


mysql-test/r/explain.result:
  Remove the extended Note, since explain returns error.
  New test case.
mysql-test/r/func_gconcat.result:
  Remove the extended Note, since explain returns error.
mysql-test/r/subselect3.result:
  Remove the extended Note, since explain returns error.
mysql-test/t/explain.test:
  New test case.
sql/sql_parse.cc:
  Skip the extended description if we have an error.

mysql-test/r/explain.result

@@ -180,7 +180,6 @@ ERROR 42000: Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP col
 SHOW WARNINGS;
 Level	Code	Message
 Error	1140	Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause
-Note	1003	select 1 AS `1` from `test`.`t1` where <not>(<exists>(...))
 SET SESSION sql_mode=@old_sql_mode;
 DROP TABLE t1;
 End of 5.0 tests.
@@ -318,3 +317,17 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
 End of 5.1 tests.
+#
+# Bug#11829785 EXPLAIN EXTENDED CRASH WITH RIGHT OUTER JOIN, SUBQUERIES
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (0), (0);
+PREPARE s FROM 
+'EXPLAIN EXTENDED
+SELECT SUBSTRING(1, (SELECT 1 FROM t1 a1 RIGHT OUTER JOIN t1 ON 0)) AS d
+FROM t1 WHERE 0 > ANY (SELECT @a FROM t1)';
+EXECUTE s;
+ERROR 21000: Subquery returns more than 1 row
+DEALLOCATE PREPARE s;
+DROP TABLE t1;
+#

mysql-test/r/func_gconcat.result

@@ -1056,7 +1056,6 @@ ERROR HY000: Only constant XPATH queries are supported
 SHOW WARNINGS;
 Level	Code	Message
 Error	1105	Only constant XPATH queries are supported
-Note	1003	select updatexml('1',`test`.`t1`.`a`,'1') AS `UPDATEXML('1', a, '1')` from `test`.`t1` order by (select group_concat(1 separator ',') from `test`.`t1`)
 DROP TABLE t1;
 End of 5.1 tests
 DROP TABLE IF EXISTS t1, t2;

mysql-test/r/subselect3.result

@@ -865,9 +865,6 @@ Level	Code	Message
 Note	1276	Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #2
 Note	1276	Field or reference 'test.t1.c' of SELECT #3 was resolved in SELECT #2
 Error	1054	Unknown column 'c' in 'field list'
-Note	1003	select `c` AS `c` from (select (select count(`test`.`t1`.`a`) from dual group by `c`) AS `(SELECT COUNT(a) FROM 
-(SELECT COUNT(b) FROM t1) AS x GROUP BY c
-)` from `test`.`t1` group by `test`.`t1`.`b`) `y`
 DROP TABLE t1;
 End of 5.0 tests
 create table t0 (a int);

mysql-test/t/explain.test

 #
-# Test of different EXPLAIN's
+# Test of different EXPLAINs
 
 --disable_warnings
 drop table if exists t1;
@@ -275,3 +275,24 @@ DEALLOCATE PREPARE stmt;
 DROP TABLE t1;
 
 --echo End of 5.1 tests.
+
+--echo #
+--echo # Bug#11829785 EXPLAIN EXTENDED CRASH WITH RIGHT OUTER JOIN, SUBQUERIES
+--echo #
+
+CREATE TABLE t1(a INT);
+
+INSERT INTO t1 VALUES (0), (0);
+
+PREPARE s FROM 
+'EXPLAIN EXTENDED
+SELECT SUBSTRING(1, (SELECT 1 FROM t1 a1 RIGHT OUTER JOIN t1 ON 0)) AS d
+FROM t1 WHERE 0 > ANY (SELECT @a FROM t1)';
+
+--error ER_SUBQUERY_NO_1_ROW
+EXECUTE s;
+
+DEALLOCATE PREPARE s;
+DROP TABLE t1;
+
+--echo #

sql/sql_parse.cc

@@ -4434,7 +4434,11 @@ static bool execute_sqlcom_select(THD *thd, TABLE_LIST *all_tables)
         return 1;                               /* purecov: inspected */
       thd->send_explain_fields(result);
       res= mysql_explain_union(thd, &thd->lex->unit, result);
-      if (lex->describe & DESCRIBE_EXTENDED)
+      /*
+        The code which prints the extended description is not robust
+        against malformed queries, so skip it if we have an error.
+      */
+      if (!res && (lex->describe & DESCRIBE_EXTENDED))
       {
         char buff[1024];
         String str(buff,(uint32) sizeof(buff), system_charset_info);