MDEV-5104 crash in Item_field::used_tables with broken order by

Analysis:
st_select_lex_unit::prepare() computes can_skip_order_by as TRUE.
As a result join->prepare() gets called with order == NULL, and
doesn't do name resolution for the inner ORDER clause. Due to this
the prepare phase doesn't detect that the query references non-exiting
function and field.
  
Later join->optimize() calls update_used_tables() for a non-resolved
Item_field, which understandably has no Field object. This call results
in a crash.

Solution:
Resolve unnecessary ORDER BY clauses to detect if they reference non-exising
objects. Then remove such clauses from the JOIN object.

mysql-test/r/group_by.result

@@ -2407,4 +2407,9 @@ a
 200
 set optimizer_switch=@save_optimizer_switch;
 DROP TABLE t1,t2;
+#
+# MDEV-5104 crash in Item_field::used_tables with broken order by
+#
+(select 1 order by x(y)) order by 1;
+ERROR 42S22: Unknown column 'y' in 'order clause'
 # End of 5.3 tests

mysql-test/r/subselect.result

@@ -193,7 +193,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 NULL	UNION RESULT	<union1,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)) order by `a`)
+Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)))
 select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
 (select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
 3	1

mysql-test/r/subselect_no_mat.result

@@ -200,7 +200,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 NULL	UNION RESULT	<union1,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)) order by `a`)
+Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)))
 select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
 (select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
 3	1

mysql-test/r/subselect_no_opts.result

@@ -196,7 +196,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 NULL	UNION RESULT	<union1,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)) order by `a`)
+Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)))
 select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
 (select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
 3	1

mysql-test/r/subselect_no_scache.result

@@ -199,7 +199,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 NULL	UNION RESULT	<union1,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)) order by `a`)
+Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)))
 select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
 (select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
 3	1

mysql-test/r/subselect_no_semijoin.result

@@ -196,7 +196,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 4	SUBQUERY	t2	ALL	NULL	NULL	NULL	NULL	2	100.00	
 NULL	UNION RESULT	<union1,3>	ALL	NULL	NULL	NULL	NULL	NULL	NULL	
 Warnings:
-Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)) order by `a`)
+Note	1003	(select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t2` where (`test`.`t2`.`b` = (select `test`.`t3`.`a` from `test`.`t3` order by 1 desc limit 1))) union (select `test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t4` where (`test`.`t4`.`b` = (select (max(`test`.`t2`.`a`) * 4) from `test`.`t2`)))
 select (select a from t3 where a<t2.a*4 order by 1 desc limit 1), a from t2;
 (select a from t3 where a<t2.a*4 order by 1 desc limit 1)	a
 3	1

mysql-test/t/group_by.test

@@ -1595,4 +1595,11 @@ set optimizer_switch=@save_optimizer_switch;
 
 DROP TABLE t1,t2;
 
+--echo #
+--echo # MDEV-5104 crash in Item_field::used_tables with broken order by
+--echo #
+
+--error ER_BAD_FIELD_ERROR
+(select 1 order by x(y)) order by 1;
+
 --echo # End of 5.3 tests

sql/item_subselect.cc

@@ -2928,6 +2928,7 @@ int subselect_single_select_engine::prepare()
 		    select_lex->order_list.elements +
 		    select_lex->group_list.elements,
 		    select_lex->order_list.first,
+                    false,
 		    select_lex->group_list.first,
 		    select_lex->having,
 		    NULL, select_lex,

sql/sql_select.cc

@@ -556,8 +556,8 @@ int
 JOIN::prepare(Item ***rref_pointer_array,
 	      TABLE_LIST *tables_init,
 	      uint wild_num, COND *conds_init, uint og_num,
-	      ORDER *order_init, ORDER *group_init,
-	      Item *having_init,
+	      ORDER *order_init, bool skip_order_by,
+              ORDER *group_init, Item *having_init,
 	      ORDER *proc_param_init, SELECT_LEX *select_lex_arg,
 	      SELECT_LEX_UNIT *unit_arg)
 {
@@ -672,6 +672,15 @@ JOIN::prepare(Item ***rref_pointer_array,
 
   ref_pointer_array= *rref_pointer_array;
 
+  /* Resolve the ORDER BY that was skipped, then remove it. */
+  if (skip_order_by && select_lex != select_lex->master_unit()->global_parameters)
+  {
+    if (setup_order(thd, (*rref_pointer_array), tables_list, fields_list,
+                    all_fields, select_lex->order_list.first))
+      DBUG_RETURN(-1);
+    select_lex->order_list.empty();
+  }
+
   if (having)
   {
     nesting_map save_allow_sum_func= thd->lex->allow_sum_func;
@@ -2952,7 +2961,7 @@ mysql_select(THD *thd, Item ***rref_pointer_array,
       else
       {
         if ((err= join->prepare(rref_pointer_array, tables, wild_num,
-                                conds, og_num, order, group, having,
+                                conds, og_num, order, false, group, having,
                                 proc_param, select_lex, unit)))
 	{
 	  goto err;
@@ -2976,7 +2985,7 @@ mysql_select(THD *thd, Item ***rref_pointer_array,
     thd_proc_info(thd, "init");
     thd->lex->used_tables=0;
     if ((err= join->prepare(rref_pointer_array, tables, wild_num,
-                            conds, og_num, order, group, having, proc_param,
+                            conds, og_num, order, false, group, having, proc_param,
                             select_lex, unit)))
     {
       goto err;

sql/sql_select.h

@@ -1294,8 +1294,8 @@ public:
   }
 
   int prepare(Item ***rref_pointer_array, TABLE_LIST *tables, uint wind_num,
-	      COND *conds, uint og_num, ORDER *order, ORDER *group,
-	      Item *having, ORDER *proc_param, SELECT_LEX *select,
+	      COND *conds, uint og_num, ORDER *order, bool skip_order_by,
+              ORDER *group, Item *having, ORDER *proc_param, SELECT_LEX *select,
 	      SELECT_LEX_UNIT *unit);
   bool prepare_stage2();
   int optimize();

sql/sql_union.cc

@@ -318,6 +318,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
                                sl->group_list.elements,
                                can_skip_order_by ?
                                NULL : sl->order_list.first,
+                               can_skip_order_by,
                                sl->group_list.first,
                                sl->having,
                                (is_union_select ? NULL :
@@ -501,7 +502,7 @@ bool st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
 		  0, 0,
                   global_parameters->order_list.elements, // og_num
                   global_parameters->order_list.first,    // order
-		  NULL, NULL, NULL,
+                  false, NULL, NULL, NULL,
 		  fake_select_lex, this);
 	fake_select_lex->table_list.empty();
       }