MDEV-11078: NULL NOT IN (non-empty subquery) should never return results

Disabling the cond guards during the creation of Tricond Item for
constant and NULL left expression items

mysql-test/r/subselect4.result

@@ -2449,5 +2449,39 @@ EXECUTE stmt;
 i
 6
 drop table t1, t2, t3;
+#
+# MDEV-11078: NULL NOT IN (non-empty subquery) should never return results
+#
+create table t1(a int,b int);
+create table t2(a int,b int);
+insert into t1 value (1,2);
+select (NULL)  in (select 1 from t1);
+(NULL)  in (select 1 from t1)
+NULL
+select (null)  in (select 1 from t2);
+(null)  in (select 1 from t2)
+0
+select 1 in (select 1 from t1);
+1 in (select 1 from t1)
+1
+select 1 in (select 1 from t2);
+1 in (select 1 from t2)
+0
+select 1 from dual where null in (select 1 from t1);
+1
+select 1 from dual where null in (select 1 from t2);
+1
+select (null,null) in (select * from t1);
+(null,null) in (select * from t1)
+NULL
+select (null,null) in (select * from t2);
+(null,null) in (select * from t2)
+0
+select 1 from dual where null not in (select 1 from t1);
+1
+select 1 from dual where null not in (select 1 from t2);
+1
+1
+drop table t1,t2;
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

mysql-test/t/subselect4.test

@@ -2000,5 +2000,24 @@ EXECUTE stmt;
 
 drop table t1, t2, t3;
 
+--echo #
+--echo # MDEV-11078: NULL NOT IN (non-empty subquery) should never return results
+--echo #
+
+create table t1(a int,b int);
+create table t2(a int,b int);
+insert into t1 value (1,2);
+select (NULL)  in (select 1 from t1);
+select (null)  in (select 1 from t2);
+select 1 in (select 1 from t1);
+select 1 in (select 1 from t2);
+select 1 from dual where null in (select 1 from t1);
+select 1 from dual where null in (select 1 from t2);
+select (null,null) in (select * from t1);
+select (null,null) in (select * from t2);
+select 1 from dual where null not in (select 1 from t1);
+select 1 from dual where null not in (select 1 from t2);
+drop table t1,t2;
+
 SET optimizer_switch= @@global.optimizer_switch;
 set @@tmp_table_size= @@global.tmp_table_size;

sql/item_subselect.cc

@@ -2035,6 +2035,7 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
         We can encounter "NULL IN (SELECT ...)". Wrap the added condition
         within a trig_cond.
       */
+      disable_cond_guard_for_const_null_left_expr(0);
       item= new Item_func_trig_cond(item, get_cond_guard(0));
     }
 
@@ -2059,6 +2060,7 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
 	having= new Item_is_not_null_test(this, having);
         if (left_expr->maybe_null)
         {
+          disable_cond_guard_for_const_null_left_expr(0);
           if (!(having= new Item_func_trig_cond(having,
                                                 get_cond_guard(0))))
             DBUG_RETURN(true);
@@ -2077,6 +2079,7 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
       */
       if (!abort_on_null && left_expr->maybe_null)
       {
+        disable_cond_guard_for_const_null_left_expr(0);
         if (!(item= new Item_func_trig_cond(item, get_cond_guard(0))))
           DBUG_RETURN(true);
       }
@@ -2103,6 +2106,7 @@ Item_in_subselect::create_single_in_to_exists_cond(JOIN *join,
                                             (char *)"<result>"));
         if (!abort_on_null && left_expr->maybe_null)
         {
+          disable_cond_guard_for_const_null_left_expr(0);
           if (!(new_having= new Item_func_trig_cond(new_having,
                                                     get_cond_guard(0))))
             DBUG_RETURN(true);
@@ -2299,6 +2303,7 @@ Item_in_subselect::create_row_in_to_exists_cond(JOIN * join,
       Item *col_item= new Item_cond_or(item_eq, item_isnull);
       if (!abort_on_null && left_expr->element_index(i)->maybe_null)
       {
+        disable_cond_guard_for_const_null_left_expr(i);
         if (!(col_item= new Item_func_trig_cond(col_item, get_cond_guard(i))))
           DBUG_RETURN(true);
       }
@@ -2313,6 +2318,7 @@ Item_in_subselect::create_row_in_to_exists_cond(JOIN * join,
                                                 (char *)"<list ref>"));
       if (!abort_on_null && left_expr->element_index(i)->maybe_null)
       {
+        disable_cond_guard_for_const_null_left_expr(i);
         if (!(item_nnull_test= 
               new Item_func_trig_cond(item_nnull_test, get_cond_guard(i))))
           DBUG_RETURN(true);
@@ -2373,6 +2379,7 @@ Item_in_subselect::create_row_in_to_exists_cond(JOIN * join,
         */
         if (left_expr->element_index(i)->maybe_null)
         {
+          disable_cond_guard_for_const_null_left_expr(i);
           if (!(item= new Item_func_trig_cond(item, get_cond_guard(i))))
             DBUG_RETURN(true);
           if (!(having_col_item= 

sql/item_subselect.h

@@ -596,6 +596,14 @@ class Item_in_subselect :public Item_exists_subselect
   void set_first_execution() { if (first_execution) first_execution= FALSE; }
   bool expr_cache_is_needed(THD *thd);
   inline bool left_expr_has_null();
+  void disable_cond_guard_for_const_null_left_expr(int i)
+  {
+    if (left_expr->const_item() && !left_expr->is_expensive())
+    {
+      if (left_expr->element_index(i)->is_null())
+        set_cond_guard_var(i,FALSE);
+    }
+  }
   
   int optimize(double *out_rows, double *cost);
   /*