A change in IF behaviour that several users asked for ...

Docs/manual.texi

@@ -46924,6 +46924,14 @@ not yet 100% confident in this code.
 * News-3.23.0::                 Changes in release 3.23.0
 @end menu
 
+@node News-3.23.53, News-3.23.52, News-3.23.x, News-3.23.x
+@appendixsubsec Changes in release 3.23.53
+@itemize @bullet
+@item
+Changed behaviour that  IF(condition,column,NULL) returns column type
+@end itemize
+
+
 @node News-3.23.52, News-3.23.51, News-3.23.x, News-3.23.x
 @appendixsubsec Changes in release 3.23.52
 @itemize @bullet

mysql-test/r/func_if.result

@@ -33,3 +33,5 @@ aa
 aaa
 sum(if(num is null,0.00,num))
 144.54
+min(if(y -x > 5,y,NULL))	max(if(y - x > 5,y,NULL))
+6	56

mysql-test/t/func_if.test

@@ -28,3 +28,7 @@ create table t1 (num  double(12,2));
 insert into t1 values (144.54);
 select sum(if(num is null,0.00,num)) from t1;
 drop table t1;
+create table t1 (x int, y int);
+insert into t1 values (0,6),(10,16),(20,26),(30,10),(40,46),(50,56);
+select min(if(y -x > 5,y,NULL)), max(if(y - x > 5,y,NULL)) from t1;
+drop table t1;

sql/item_cmpfunc.cc

@@ -494,6 +494,12 @@ Item_func_if::fix_length_and_dec()
   decimals=max(args[1]->decimals,args[2]->decimals);
   enum Item_result arg1_type=args[1]->result_type();
   enum Item_result arg2_type=args[2]->result_type();
+  bool null1=args[1]->null_value;
+  bool null2=args[2]->null_value;
+  if (null1 && !null2)
+    arg1_type=arg2_type;
+  else if (!null1 && null2)
+    arg2_type=arg1_type;
   binary=1;
   if (arg1_type == STRING_RESULT || arg2_type == STRING_RESULT)
   {