Fixed bug #24856: the result set of a ROLLUP query with DISTINCT could lack

some rollup rows (rows with NULLs for grouping attributes) if GROUP BY
list contained constant expressions.

This happened because the results of constant expressions were not put
in the temporary table used for duplicate elimination. In fact a constant
item from the GROUP BY list of a ROLLUP query can be replaced for an
Item_null_result object when a rollup row is produced . 

Now the JOIN::rollup_init function wraps any constant item referenced in
the GROYP BY list of a ROLLUP query into an Item_func object of a special
class that is never detected as constant item. This ensures creation of
fields for such  constant items in temporary tables and guarantees right
results when the result of the rollup operation first has to be written
into a temporary table, e.g. in the cases when duplicate elimination is
required.  

1 files changed, 25 insertions, 0 deletions

diff --git a/sql/item_func.h b/sql/item_func.h
index 467b88eda76..ebe3a589aa1 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -590,6 +590,31 @@ public:
 };
 
 
+/* 
+  Objects of this class are used for ROLLUP queries to wrap up 
+  each constant item referred to in GROUP BY list. 
+*/
+
+class Item_func_rollup_const :public Item_func
+{
+public:
+  Item_func_rollup_const(Item *a) :Item_func(a)
+    { name= a->name; }
+  double val() { return args[0]->val(); }
+  longlong val_int() { return args[0]->val_int(); }
+  String *val_str(String *str) { return args[0]->val_str(str); }
+  const char *func_name() const { return "rollup_const"; }
+  bool const_item() const { return 0; }
+  Item_result result_type() const { return args[0]->result_type(); }
+  void fix_length_and_dec()
+  {
+    collation= args[0]->collation;
+    max_length= args[0]->max_length;
+    decimals=args[0]->decimals; 
+  }
+};
+
+
 class Item_func_length :public Item_int_func
 {
   String value;