BUG#836532: Crash in Item_equal_fields_iterator::get_curr_field with semijoin+materialization

- Item_in_subselect::inject_in_to_exists_cond() should not call 
  ((Item_cond*)join->conds)->argument_list()->concat(join->cond_equal->current_level)
  as that makes two lists share their tail, and the cond_equal list
  will end up containing non-Item_equal objects when substitute_for_best_equal_field()
  walks through join->conds and replaces all Item_equal objects with Item_func_eq objects.
  - So, instead of using List::concat(), manually copy entries from one list to another.

mysql-test/r/subselect_mat.result

@@ -3,7 +3,7 @@ set @subselect_sj_mat_tmp= @@optimizer_switch;
 set optimizer_switch=ifnull(@subselect_mat_test_optimizer_switch_value, 'semijoin=on,firstmatch=on,loosescan=on');
 set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 set @optimizer_switch_local_default= @@optimizer_switch;
-drop table if exists t1, t2, t3, t4, t1i, t2i, t3i;
+drop table if exists t1, t2, t3, t4, t5, t1i, t2i, t3i;
 drop table if exists columns;
 drop table if exists t1_16, t2_16, t3_16;
 drop view if exists v1, v2, v1m, v2m;
@@ -1627,6 +1627,35 @@ a
 1
 1
 DROP TABLE t1,t2,t3,t4,t5;
+#
+# BUG#836532: Crash in Item_equal_fields_iterator::get_curr_field with semijoin+materialization
+#
+CREATE TABLE t2 (a int);
+INSERT INTO t2 VALUES ('a'),('a');
+Warnings:
+Warning	1366	Incorrect integer value: 'a' for column 'a' at row 1
+Warning	1366	Incorrect integer value: 'a' for column 'a' at row 2
+CREATE TABLE t4 (a varchar(1));
+INSERT INTO t4 VALUES ('m'),('o');
+CREATE TABLE t3 (a varchar(1) , b varchar(1) ) ;
+INSERT INTO t3 VALUES ('b','b');
+CREATE TABLE t5 (a varchar(1), KEY (a)) ;
+INSERT INTO t5 VALUES ('d'),('e');
+SELECT *
+FROM t2
+WHERE t2.a = ALL (
+SELECT t4.a
+FROM t4
+WHERE t4.a IN (
+SELECT t3.a
+FROM t3 , t5
+WHERE ( t5.a = t3.b )
+)
+);
+a
+0
+0
+DROP TABLE t2,t3,t4,t5;
 set optimizer_switch=@subselect_sj_mat_tmp;
 set @subselect_mat_test_optimizer_switch_value=null;
 set @@optimizer_switch='materialization=on,in_to_exists=off,semijoin=off';

mysql-test/r/subselect_sj_mat.result

@@ -2,7 +2,7 @@ set @subselect_sj_mat_tmp= @@optimizer_switch;
 set optimizer_switch=ifnull(@subselect_mat_test_optimizer_switch_value, 'semijoin=on,firstmatch=on,loosescan=on');
 set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 set @optimizer_switch_local_default= @@optimizer_switch;
-drop table if exists t1, t2, t3, t4, t1i, t2i, t3i;
+drop table if exists t1, t2, t3, t4, t5, t1i, t2i, t3i;
 drop table if exists columns;
 drop table if exists t1_16, t2_16, t3_16;
 drop view if exists v1, v2, v1m, v2m;
@@ -1665,4 +1665,33 @@ a
 1
 1
 DROP TABLE t1,t2,t3,t4,t5;
+#
+# BUG#836532: Crash in Item_equal_fields_iterator::get_curr_field with semijoin+materialization
+#
+CREATE TABLE t2 (a int);
+INSERT INTO t2 VALUES ('a'),('a');
+Warnings:
+Warning	1366	Incorrect integer value: 'a' for column 'a' at row 1
+Warning	1366	Incorrect integer value: 'a' for column 'a' at row 2
+CREATE TABLE t4 (a varchar(1));
+INSERT INTO t4 VALUES ('m'),('o');
+CREATE TABLE t3 (a varchar(1) , b varchar(1) ) ;
+INSERT INTO t3 VALUES ('b','b');
+CREATE TABLE t5 (a varchar(1), KEY (a)) ;
+INSERT INTO t5 VALUES ('d'),('e');
+SELECT *
+FROM t2
+WHERE t2.a = ALL (
+SELECT t4.a
+FROM t4
+WHERE t4.a IN (
+SELECT t3.a
+FROM t3 , t5
+WHERE ( t5.a = t3.b )
+)
+);
+a
+0
+0
+DROP TABLE t2,t3,t4,t5;
 set optimizer_switch=@subselect_sj_mat_tmp;

mysql-test/t/subselect_sj_mat.test

@@ -9,7 +9,7 @@ set optimizer_switch='mrr=on,mrr_sort_keys=on,index_condition_pushdown=on';
 set @optimizer_switch_local_default= @@optimizer_switch;
 
 --disable_warnings
-drop table if exists t1, t2, t3, t4, t1i, t2i, t3i;
+drop table if exists t1, t2, t3, t4, t5, t1i, t2i, t3i;
 drop table if exists columns;
 drop table if exists t1_16, t2_16, t3_16;
 drop view if exists v1, v2, v1m, v2m;
@@ -1319,5 +1319,35 @@ WHERE (a) IN (
 
 DROP TABLE t1,t2,t3,t4,t5;
 
+--echo #
+--echo # BUG#836532: Crash in Item_equal_fields_iterator::get_curr_field with semijoin+materialization
+--echo #
+
+CREATE TABLE t2 (a int);
+INSERT INTO t2 VALUES ('a'),('a');
+
+CREATE TABLE t4 (a varchar(1));
+INSERT INTO t4 VALUES ('m'),('o');
+
+CREATE TABLE t3 (a varchar(1) , b varchar(1) ) ;
+INSERT INTO t3 VALUES ('b','b');
+
+CREATE TABLE t5 (a varchar(1), KEY (a)) ;
+INSERT INTO t5 VALUES ('d'),('e');
+
+SELECT *
+FROM t2
+WHERE t2.a = ALL (
+        SELECT t4.a
+        FROM t4
+        WHERE t4.a IN (
+                SELECT t3.a
+                FROM t3 , t5
+                WHERE ( t5.a = t3.b )
+        )
+);
+
+DROP TABLE t2,t3,t4,t5;
+
 set optimizer_switch=@subselect_sj_mat_tmp;
 

sql/item_subselect.cc

@@ -2264,7 +2264,12 @@ bool Item_in_subselect::inject_in_to_exists_cond(JOIN *join_arg)
     {
       /* The argument list of the top-level AND may change after fix fields. */
       and_args= ((Item_cond*) join_arg->conds)->argument_list();
-      and_args->concat((List<Item> *) &join_arg->cond_equal->current_level);
+      List_iterator<Item_equal> li(join_arg->cond_equal->current_level);
+      Item_equal *elem;
+      while ((elem= li++))
+      {
+        and_args->push_back(elem);
+      }
     }
   }
 

sql/sql_list.h

@@ -310,6 +310,26 @@ public:
   friend class error_list;
   friend class error_list_iterator;
 
+  /*
+    Debugging help: return N-th element in the list, or NULL if the list has
+    less than N elements.
+  */
+  inline void *nth_element(int n)
+  {
+    list_node *node= first;
+    void *data;
+    for (int i=0; i <= n; i++)
+    {
+      if (node == &end_of_list)
+      {
+        data= NULL;
+        break;
+      }
+      data= node->info;
+      node= node->next;
+    }
+    return data;
+  }
 #ifdef LIST_EXTRA_DEBUG
   /*
     Check list invariants and print results into trace. Invariants are:
@@ -488,6 +508,7 @@ public:
     }
     empty();
   }
+  inline T *nth_element(int n) { return (T*)base_list::nth_element(n); }
 };