MDEV-4284 Assertion `cmp_items[(uint)cmp_type]' fails in sql/item_cmpfunc.cc

Flip the switch and create Item_cache based on the argument's cmp_type, not argument's result_type().
Fix subselect_engine to calculate cmp_type correctly

sql/item_subselect.h:
  mdev:4284

1 files changed, 4 insertions, 1 deletions

diff --git a/sql/item_subselect.h b/sql/item_subselect.h
index 1da129380e7..25852b55d98 100644
--- a/sql/item_subselect.h
+++ b/sql/item_subselect.h
@@ -286,6 +286,7 @@ public:
   bool val_bool();
   bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate);
   enum Item_result result_type() const;
+  enum Item_result cmp_type() const;
   enum_field_types field_type() const;
   void fix_length_and_dec();
 
@@ -698,6 +699,7 @@ protected:
   THD *thd; /* pointer to current THD */
   Item_subselect *item; /* item, that use this engine */
   enum Item_result res_type; /* type of results */
+  enum Item_result cmp_type; /* how to compare the results */
   enum_field_types res_field_type; /* column type of the results */
   bool maybe_null; /* may be null (first item in select) */
 public:
@@ -712,7 +714,7 @@ public:
   {
     result= res;
     item= si;
-    res_type= STRING_RESULT;
+    cmp_type= res_type= STRING_RESULT;
     res_field_type= MYSQL_TYPE_VAR_STRING;
     maybe_null= 0;
     set_thd(thd_arg);
@@ -752,6 +754,7 @@ public:
   virtual uint cols()= 0; /* return number of columns in select */
   virtual uint8 uncacheable()= 0; /* query is uncacheable */
   enum Item_result type() { return res_type; }
+  enum Item_result cmptype() { return cmp_type; }
   enum_field_types field_type() { return res_field_type; }
   virtual void exclude()= 0;
   virtual bool may_be_null() { return maybe_null; };