MDEV-7846: Server crashes in Item_subselect::fix_fields or fails with Thread stack overrun

Substitute into transformed subselects original left expression and than register its change in case it was substituted.

mysql-test/r/subselect.result

@@ -7053,3 +7053,31 @@ WHERE h.host in (SELECT host FROM mysql.user)
 ) AS sq
 FROM mysql.host h GROUP BY h.host;
 sq
+#
+# MDEV-7846:Server crashes in Item_subselect::fix
+#_fields or fails with Thread stack overrun
+#
+CREATE TABLE t1 (column1 INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (3),(9);
+CREATE TABLE t2 (column2 INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(4);
+CREATE TABLE t3 (column3 INT) ENGINE=MyISAM;
+INSERT INTO t3 VALUES (6),(8);
+CREATE TABLE t4 (column4 INT) ENGINE=MyISAM;
+INSERT INTO t4 VALUES (2),(5);
+PREPARE stmt FROM "
+SELECT ( 
+  SELECT MAX( table1.column1 ) AS field1 
+  FROM t1 AS table1
+  WHERE table3.column3 IN ( SELECT table2.column2 AS field2 FROM t2 AS table2 ) 
+) AS sq
+FROM t3 AS table3, t4 AS table4 GROUP BY sq
+";
+EXECUTE stmt;
+sq
+NULL
+EXECUTE stmt;
+sq
+NULL
+deallocate prepare stmt;
+drop table t1,t2,t3,t4;

mysql-test/r/subselect_no_mat.result

@@ -7050,6 +7050,34 @@ WHERE h.host in (SELECT host FROM mysql.user)
 ) AS sq
 FROM mysql.host h GROUP BY h.host;
 sq
+#
+# MDEV-7846:Server crashes in Item_subselect::fix
+#_fields or fails with Thread stack overrun
+#
+CREATE TABLE t1 (column1 INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (3),(9);
+CREATE TABLE t2 (column2 INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(4);
+CREATE TABLE t3 (column3 INT) ENGINE=MyISAM;
+INSERT INTO t3 VALUES (6),(8);
+CREATE TABLE t4 (column4 INT) ENGINE=MyISAM;
+INSERT INTO t4 VALUES (2),(5);
+PREPARE stmt FROM "
+SELECT ( 
+  SELECT MAX( table1.column1 ) AS field1 
+  FROM t1 AS table1
+  WHERE table3.column3 IN ( SELECT table2.column2 AS field2 FROM t2 AS table2 ) 
+) AS sq
+FROM t3 AS table3, t4 AS table4 GROUP BY sq
+";
+EXECUTE stmt;
+sq
+NULL
+EXECUTE stmt;
+sq
+NULL
+deallocate prepare stmt;
+drop table t1,t2,t3,t4;
 set optimizer_switch=default;
 select @@optimizer_switch like '%materialization=on%';
 @@optimizer_switch like '%materialization=on%'

mysql-test/r/subselect_no_opts.result

@@ -7048,4 +7048,32 @@ WHERE h.host in (SELECT host FROM mysql.user)
 ) AS sq
 FROM mysql.host h GROUP BY h.host;
 sq
+#
+# MDEV-7846:Server crashes in Item_subselect::fix
+#_fields or fails with Thread stack overrun
+#
+CREATE TABLE t1 (column1 INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (3),(9);
+CREATE TABLE t2 (column2 INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(4);
+CREATE TABLE t3 (column3 INT) ENGINE=MyISAM;
+INSERT INTO t3 VALUES (6),(8);
+CREATE TABLE t4 (column4 INT) ENGINE=MyISAM;
+INSERT INTO t4 VALUES (2),(5);
+PREPARE stmt FROM "
+SELECT ( 
+  SELECT MAX( table1.column1 ) AS field1 
+  FROM t1 AS table1
+  WHERE table3.column3 IN ( SELECT table2.column2 AS field2 FROM t2 AS table2 ) 
+) AS sq
+FROM t3 AS table3, t4 AS table4 GROUP BY sq
+";
+EXECUTE stmt;
+sq
+NULL
+EXECUTE stmt;
+sq
+NULL
+deallocate prepare stmt;
+drop table t1,t2,t3,t4;
 set @optimizer_switch_for_subselect_test=null;

mysql-test/r/subselect_no_scache.result

@@ -7059,6 +7059,34 @@ WHERE h.host in (SELECT host FROM mysql.user)
 ) AS sq
 FROM mysql.host h GROUP BY h.host;
 sq
+#
+# MDEV-7846:Server crashes in Item_subselect::fix
+#_fields or fails with Thread stack overrun
+#
+CREATE TABLE t1 (column1 INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (3),(9);
+CREATE TABLE t2 (column2 INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(4);
+CREATE TABLE t3 (column3 INT) ENGINE=MyISAM;
+INSERT INTO t3 VALUES (6),(8);
+CREATE TABLE t4 (column4 INT) ENGINE=MyISAM;
+INSERT INTO t4 VALUES (2),(5);
+PREPARE stmt FROM "
+SELECT ( 
+  SELECT MAX( table1.column1 ) AS field1 
+  FROM t1 AS table1
+  WHERE table3.column3 IN ( SELECT table2.column2 AS field2 FROM t2 AS table2 ) 
+) AS sq
+FROM t3 AS table3, t4 AS table4 GROUP BY sq
+";
+EXECUTE stmt;
+sq
+NULL
+EXECUTE stmt;
+sq
+NULL
+deallocate prepare stmt;
+drop table t1,t2,t3,t4;
 set optimizer_switch=default;
 select @@optimizer_switch like '%subquery_cache=on%';
 @@optimizer_switch like '%subquery_cache=on%'

mysql-test/r/subselect_no_semijoin.result

@@ -7048,5 +7048,33 @@ WHERE h.host in (SELECT host FROM mysql.user)
 ) AS sq
 FROM mysql.host h GROUP BY h.host;
 sq
+#
+# MDEV-7846:Server crashes in Item_subselect::fix
+#_fields or fails with Thread stack overrun
+#
+CREATE TABLE t1 (column1 INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (3),(9);
+CREATE TABLE t2 (column2 INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(4);
+CREATE TABLE t3 (column3 INT) ENGINE=MyISAM;
+INSERT INTO t3 VALUES (6),(8);
+CREATE TABLE t4 (column4 INT) ENGINE=MyISAM;
+INSERT INTO t4 VALUES (2),(5);
+PREPARE stmt FROM "
+SELECT ( 
+  SELECT MAX( table1.column1 ) AS field1 
+  FROM t1 AS table1
+  WHERE table3.column3 IN ( SELECT table2.column2 AS field2 FROM t2 AS table2 ) 
+) AS sq
+FROM t3 AS table3, t4 AS table4 GROUP BY sq
+";
+EXECUTE stmt;
+sq
+NULL
+EXECUTE stmt;
+sq
+NULL
+deallocate prepare stmt;
+drop table t1,t2,t3,t4;
 set @optimizer_switch_for_subselect_test=null;
 set @join_cache_level_for_subselect_test=NULL;

mysql-test/t/subselect.test

@@ -5930,3 +5930,37 @@ SELECT
     WHERE h.host in (SELECT host FROM mysql.user)
   ) AS sq
 FROM mysql.host h GROUP BY h.host;
+
+
+--echo #
+--echo # MDEV-7846:Server crashes in Item_subselect::fix
+--echo #_fields or fails with Thread stack overrun
+--echo #
+CREATE TABLE t1 (column1 INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (3),(9);
+
+CREATE TABLE t2 (column2 INT) ENGINE=MyISAM;
+
+INSERT INTO t2 VALUES (1),(4);
+
+CREATE TABLE t3 (column3 INT) ENGINE=MyISAM;
+INSERT INTO t3 VALUES (6),(8);
+
+CREATE TABLE t4 (column4 INT) ENGINE=MyISAM;
+INSERT INTO t4 VALUES (2),(5);
+
+
+PREPARE stmt FROM "
+SELECT ( 
+  SELECT MAX( table1.column1 ) AS field1 
+  FROM t1 AS table1
+  WHERE table3.column3 IN ( SELECT table2.column2 AS field2 FROM t2 AS table2 ) 
+) AS sq
+FROM t3 AS table3, t4 AS table4 GROUP BY sq
+";
+
+EXECUTE stmt;
+EXECUTE stmt;
+
+deallocate prepare stmt;
+drop table t1,t2,t3,t4;

sql/item_cmpfunc.cc

@@ -1455,12 +1455,12 @@ bool Item_in_optimizer::fix_left(THD *thd, Item **ref)
        next execution we need to copy args[1]->left_expr again.
     */
     ref0= &(((Item_in_subselect *)args[1])->left_expr);
-    args[0]= ref0[0];
   }
-  if ((!args[0]->fixed && args[0]->fix_fields(thd, ref0)) ||
-      (!cache && !(cache= Item_cache::get_cache(ref0[0]))))
+  if ((!(*ref0)->fixed && (*ref0)->fix_fields(thd, ref0)) ||
+      (!cache && !(cache= Item_cache::get_cache(*ref0))))
     DBUG_RETURN(1);
-  args[0]= ref0[0];
+  if (args[0] != (*ref0))
+    current_thd->change_item_tree(args, (*ref0));
   DBUG_PRINT("info", ("actual fix fields"));
 
   cache->setup(args[0]);

sql/item_subselect.cc

@@ -1363,7 +1363,7 @@ Item_in_subselect::Item_in_subselect(Item * left_exp,
   upper_item(0)
 {
   DBUG_ENTER("Item_in_subselect::Item_in_subselect");
-  left_expr= left_exp;
+  left_expr_orig= left_expr= left_exp;
   func= &eq_creator;
   init(select_lex, new select_exists_subselect(this));
   max_columns= UINT_MAX;
@@ -1387,7 +1387,7 @@ Item_allany_subselect::Item_allany_subselect(Item * left_exp,
   :Item_in_subselect(), func_creator(fc), all(all_arg)
 {
   DBUG_ENTER("Item_allany_subselect::Item_allany_subselect");
-  left_expr= left_exp;
+  left_expr_orig= left_expr= left_exp;
   func= func_creator(all_arg);
   init(select_lex, new select_exists_subselect(this));
   max_columns= 1;
@@ -2586,15 +2586,13 @@ Item_in_subselect::select_in_like_transformer(JOIN *join)
   arena= thd->activate_stmt_arena_if_needed(&backup);
   if (!optimizer)
   {
-    result= (!(optimizer= new Item_in_optimizer(left_expr, this)));
+    result= (!(optimizer= new Item_in_optimizer(left_expr_orig, this)));
     if (result)
       goto out;
   }
 
   thd->lex->current_select= current->return_after_parsing();
   result= optimizer->fix_left(thd, optimizer->arguments());
-  /* fix_fields can change reference to left_expr, we need reassign it */
-  left_expr= optimizer->arguments()[0];
   thd->lex->current_select= current;
 
   if (changed)

sql/item_subselect.h

@@ -449,6 +449,7 @@ protected:
                                     Item **having_item);
 public:
   Item *left_expr;
+  Item *left_expr_orig;
   /* Priority of this predicate in the convert-to-semi-join-nest process. */
   int sj_convert_priority;
   /*

sql/opt_subselect.cc

@@ -1593,7 +1593,9 @@ static bool convert_subq_to_sj(JOIN *parent_join, Item_in_subselect *subq_pred)
   {
     nested_join->sj_outer_expr_list.push_back(subq_pred->left_expr);
     Item_func_eq *item_eq=
-      new Item_func_eq(subq_pred->left_expr, subq_lex->ref_pointer_array[0]);
+      new Item_func_eq(subq_pred->left_expr_orig, subq_lex->ref_pointer_array[0]);
+    if (subq_pred->left_expr_orig != subq_pred->left_expr)
+      thd->change_item_tree(item_eq->arguments(), subq_pred->left_expr);
     item_eq->in_equality_no= 0;
     sj_nest->sj_on_expr= and_items(sj_nest->sj_on_expr, item_eq);
   }