Bug#37601 Cast Is Not Done On Row Comparison

In case of ROW item each compared pair does not
check if argumet collations can be aggregated and
thus appropiriate item conversion does not happen.
The fix is to add the check and convertion for ROW
pairs.


mysql-test/r/row.result:
  test result
mysql-test/t/row.test:
  test case
sql/item.cc:
  added agg_item_set_converter() function which was a part of
  agg_item_charsets() func. The only difference is that
  agg_item_set_converter() checks and converts items 
  using already known collation.
sql/item.h:
  added agg_item_set_converter() function
sql/item_cmpfunc.cc:
  In case of ROW item each compared pair does not
  check if argumet collations can be aggregated and
  thus appropiriate item conversion does not happen.
  The fix is to add the check and convertion for ROW
  pairs.

1 files changed, 12 insertions, 1 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 3b1d18b4252..01d3e9bed52 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -490,7 +490,8 @@ int Arg_comparator::set_compare_func(Item_bool_func2 *item, Item_result type)
 	my_error(ER_OPERAND_COLUMNS, MYF(0), (*a)->element_index(i)->cols());
 	return 1;
       }
-      comparators[i].set_cmp_func(owner, (*a)->addr(i), (*b)->addr(i));
+      if (comparators[i].set_cmp_func(owner, (*a)->addr(i), (*b)->addr(i)))
+        return 1;
     }
     break;
   }
@@ -835,6 +836,16 @@ int Arg_comparator::set_cmp_func(Item_bool_func2 *owner_arg,
     get_value_func= &get_time_value;
     return 0;
   }
+  else if (type == STRING_RESULT &&
+           (*a)->result_type() == STRING_RESULT &&
+           (*b)->result_type() == STRING_RESULT)
+  {
+    DTCollation coll;
+    coll.set((*a)->collation.collation);
+    if (agg_item_set_converter(coll, owner_arg->func_name(),
+                               b, 1, MY_COLL_CMP_CONV, 1))
+      return 1;
+  }
 
   return set_compare_func(owner_arg, type);
 }