Fix for bug #9764 (DISTINCT IFNULL truncates data)

mysql-test/r/create.result:
  test result fixed
mysql-test/r/distinct.result:
  test result fixed
mysql-test/t/distinct.test:
  test case added
sql/item_cmpfunc.cc:
  max_length should be calculated differently for DECIMAL_RESULT and others

mysql-test/r/create.result

@@ -434,7 +434,7 @@ d	date	YES		NULL
 e	varchar(1)	NO			
 f	datetime	YES		NULL	
 g	time	YES		NULL	
-h	varbinary(23)	NO			
+h	longblob	NO			
 dd	time	YES		NULL	
 select * from t2;
 a	b	c	d	e	f	g	h	dd

mysql-test/r/distinct.result

@@ -464,3 +464,11 @@ SELECT DISTINCT html,SUM(rout)/(SUM(rin)+1) as 'prod' FROM t1 GROUP BY rin;
 html	prod
 1	0.0000
 drop table t1;
+create table t1 (id int, dsc varchar(50));
+insert into t1 values (1, "line number one"), (2, "line number two"), (3, "line number three");
+select distinct id, IFNULL(dsc, '-') from t1;
+id	IFNULL(dsc, '-')
+1	line number one
+2	line number two
+3	line number three
+drop table t1;

mysql-test/t/distinct.test

@@ -332,3 +332,11 @@ CREATE TABLE t1 (
 INSERT INTO t1 VALUES ('1',1,0);
 SELECT DISTINCT html,SUM(rout)/(SUM(rin)+1) as 'prod' FROM t1 GROUP BY rin;
 drop table t1;
+
+#
+# Bug 9784 DISTINCT IFNULL truncates data
+#
+create table t1 (id int, dsc varchar(50));
+insert into t1 values (1, "line number one"), (2, "line number two"), (3, "line number three");
+select distinct id, IFNULL(dsc, '-') from t1;
+drop table t1;

sql/item_cmpfunc.cc

@@ -1109,12 +1109,14 @@ void Item_func_between::print(String *str)
 void
 Item_func_ifnull::fix_length_and_dec()
 {
+  agg_result_type(&hybrid_type, args, 2);
   maybe_null=args[1]->maybe_null;
   decimals= max(args[0]->decimals, args[1]->decimals);
-  max_length= (max(args[0]->max_length - args[0]->decimals,
-                   args[1]->max_length - args[1]->decimals) +
-               decimals);
-  agg_result_type(&hybrid_type, args, 2);
+  max_length= (hybrid_type == DECIMAL_RESULT || hybrid_type == INT_RESULT) ?
+    (max(args[0]->max_length - args[0]->decimals,
+         args[1]->max_length - args[1]->decimals) + decimals) :
+    max(args[0]->max_length, args[1]->max_length);
+
   switch (hybrid_type) {
   case STRING_RESULT:
     agg_arg_charsets(collation, args, arg_count, MY_COLL_CMP_CONV);
@@ -1225,16 +1227,7 @@ Item_func_if::fix_length_and_dec()
 {
   maybe_null=args[1]->maybe_null || args[2]->maybe_null;
   decimals= max(args[1]->decimals, args[2]->decimals);
-  if (decimals == NOT_FIXED_DEC)
-  {
-    max_length= max(args[1]->max_length, args[2]->max_length);
-  }
-  else
-  {
-    max_length= (max(args[1]->max_length - args[1]->decimals,
-                   args[2]->max_length - args[2]->decimals) +
-               decimals);
-  }
+
   enum Item_result arg1_type=args[1]->result_type();
   enum Item_result arg2_type=args[2]->result_type();
   bool null1=args[1]->const_item() && args[1]->null_value;
@@ -1263,6 +1256,11 @@ Item_func_if::fix_length_and_dec()
       collation.set(&my_charset_bin);	// Number
     }
   }
+  max_length=
+    (cached_result_type == DECIMAL_RESULT || cached_result_type == INT_RESULT) ?
+    (max(args[1]->max_length - args[1]->decimals,
+         args[2]->max_length - args[2]->decimals) + decimals) :
+    max(args[1]->max_length, args[2]->max_length);
 }