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

@@ -443,3 +443,17 @@ SELECT ROW(a, 1) IN (SELECT SUM(b), 3) FROM t1 GROUP BY a;
 ROW(a, 1) IN (SELECT SUM(b), 3)
 0
 DROP TABLE t1;
+create table t1 (a varchar(200),
+b int unsigned not null primary key auto_increment)
+default character set 'utf8';
+create table t2 (c varchar(200),
+d int unsigned not null primary key auto_increment)
+default character set 'latin1';
+insert into t1 (a) values('abc');
+insert into t2 (c) values('abc');
+select * from t1,t2 where (a,b) = (c,d);
+a	b	c	d
+abc	1	abc	1
+select host,user from mysql.user where (host,user) = ('localhost','test');
+host	user
+drop table t1,t2;

mysql-test/t/row.test

@@ -237,3 +237,21 @@ SELECT ROW(a, 1) IN (SELECT SUM(b), 1) FROM t1 GROUP BY a;
 SELECT ROW(a, 1) IN (SELECT SUM(b), 3) FROM t1 GROUP BY a;
 
 DROP TABLE t1;
+
+#
+# Bug#37601 Cast Is Not Done On Row Comparison
+#
+create table t1 (a varchar(200),
+                 b int unsigned not null primary key auto_increment)
+default character set 'utf8';
+
+create table t2 (c varchar(200),
+                 d int unsigned not null primary key auto_increment)
+default character set 'latin1';
+
+insert into t1 (a) values('abc');
+insert into t2 (c) values('abc');
+select * from t1,t2 where (a,b) = (c,d);
+
+select host,user from mysql.user where (host,user) = ('localhost','test');
+drop table t1,t2;

sql/item.cc

@@ -1608,42 +1608,11 @@ bool agg_item_collations_for_comparison(DTCollation &c, const char *fname,
 }
 
 
-/* 
-  Collect arguments' character sets together.
-  We allow to apply automatic character set conversion in some cases.
-  The conditions when conversion is possible are:
-  - arguments A and B have different charsets
-  - A wins according to coercibility rules
-    (i.e. a column is stronger than a string constant,
-     an explicit COLLATE clause is stronger than a column)
-  - character set of A is either superset for character set of B,
-    or B is a string constant which can be converted into the
-    character set of A without data loss.
-    
-  If all of the above is true, then it's possible to convert
-  B into the character set of A, and then compare according
-  to the collation of A.
-  
-  For functions with more than two arguments:
-
-    collect(A,B,C) ::= collect(collect(A,B),C)
-
-  Since this function calls THD::change_item_tree() on the passed Item **
-  pointers, it is necessary to pass the original Item **'s, not copies.
-  Otherwise their values will not be properly restored (see BUG#20769).
-  If the items are not consecutive (eg. args[2] and args[5]), use the
-  item_sep argument, ie.
-
-    agg_item_charsets(coll, fname, &args[2], 2, flags, 3)
 
-*/
-
-bool agg_item_charsets(DTCollation &coll, const char *fname,
+bool agg_item_set_converter(DTCollation &coll, const char *fname,
                             Item **args, uint nargs, uint flags, int item_sep)
 {
   Item **arg, *safe_args[2];
-  if (agg_item_collations(coll, fname, args, nargs, flags, item_sep))
-    return TRUE;
 
   /*
     For better error reporting: save the first and the second argument.
@@ -1724,6 +1693,47 @@ bool agg_item_charsets(DTCollation &coll, const char *fname,
 }
 
 
+/* 
+  Collect arguments' character sets together.
+  We allow to apply automatic character set conversion in some cases.
+  The conditions when conversion is possible are:
+  - arguments A and B have different charsets
+  - A wins according to coercibility rules
+    (i.e. a column is stronger than a string constant,
+     an explicit COLLATE clause is stronger than a column)
+  - character set of A is either superset for character set of B,
+    or B is a string constant which can be converted into the
+    character set of A without data loss.
+    
+  If all of the above is true, then it's possible to convert
+  B into the character set of A, and then compare according
+  to the collation of A.
+  
+  For functions with more than two arguments:
+
+    collect(A,B,C) ::= collect(collect(A,B),C)
+
+  Since this function calls THD::change_item_tree() on the passed Item **
+  pointers, it is necessary to pass the original Item **'s, not copies.
+  Otherwise their values will not be properly restored (see BUG#20769).
+  If the items are not consecutive (eg. args[2] and args[5]), use the
+  item_sep argument, ie.
+
+    agg_item_charsets(coll, fname, &args[2], 2, flags, 3)
+
+*/
+
+bool agg_item_charsets(DTCollation &coll, const char *fname,
+                       Item **args, uint nargs, uint flags, int item_sep)
+{
+  Item **arg, *safe_args[2];
+  if (agg_item_collations(coll, fname, args, nargs, flags, item_sep))
+    return TRUE;
+
+  return agg_item_set_converter(coll, fname, args, nargs, flags, item_sep);
+}
+
+
 void Item_ident_for_show::make_field(Send_field *tmp_field)
 {
   tmp_field->table_name= tmp_field->org_table_name= table_name;

sql/item.h

@@ -1169,6 +1169,8 @@ bool agg_item_collations(DTCollation &c, const char *name,
                          Item **items, uint nitems, uint flags, int item_sep);
 bool agg_item_collations_for_comparison(DTCollation &c, const char *name,
                                         Item **items, uint nitems, uint flags);
+bool agg_item_set_converter(DTCollation &coll, const char *fname,
+                            Item **args, uint nargs, uint flags, int item_sep);
 bool agg_item_charsets(DTCollation &c, const char *name,
                        Item **items, uint nitems, uint flags, int item_sep);
 

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);
 }