BUG#32198: Comparison of DATE with DATETIME still not using indexes correctly

- Make conditions like "date_col $CMP$ 'datetime-const'" range-sargable

mysql-test/r/range.result

@@ -1135,3 +1135,21 @@ item	started	price
 A1	2005-11-01 08:00:00	1000.000
 A1	2005-11-15 00:00:00	2000.000
 DROP TABLE t1;
+
+BUG#32198 "Comparison of DATE with DATETIME still not using indexes correctly"
+
+CREATE TABLE t1 (
+id int(11) NOT NULL auto_increment,
+dateval date default NULL,
+PRIMARY KEY  (id),
+KEY dateval (dateval)
+) AUTO_INCREMENT=173;
+INSERT INTO t1 VALUES
+(1,'2007-01-01'),(2,'2007-01-02'),(3,'2007-01-03'),(4,'2007-01-04'),
+(5,'2007-01-05'),(6,'2007-01-06'),(7,'2007-01-07'),(8,'2007-01-08'),
+(9,'2007-01-09'),(10,'2007-01-10'),(11,'2007-01-11');
+This must use range access:
+explain select * from t1 where dateval >= '2007-01-01 00:00:00' and dateval <= '2007-01-02 23:59:59';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	dateval	dateval	4	NULL	2	Using where
+drop table t1;

mysql-test/t/range.test

@@ -935,4 +935,24 @@ SELECT * FROM t1 WHERE item='A1' AND started<='2005-12-02 00:00:00';
 
 DROP TABLE t1;
 
+--echo
+--echo BUG#32198 "Comparison of DATE with DATETIME still not using indexes correctly"
+--echo
+CREATE TABLE t1 (
+  id int(11) NOT NULL auto_increment,
+  dateval date default NULL,
+  PRIMARY KEY  (id),
+  KEY dateval (dateval)
+) AUTO_INCREMENT=173;
+
+INSERT INTO t1 VALUES
+(1,'2007-01-01'),(2,'2007-01-02'),(3,'2007-01-03'),(4,'2007-01-04'),
+(5,'2007-01-05'),(6,'2007-01-06'),(7,'2007-01-07'),(8,'2007-01-08'),
+(9,'2007-01-09'),(10,'2007-01-10'),(11,'2007-01-11');
+
+--echo This must use range access:
+explain select * from t1 where dateval >= '2007-01-01 00:00:00' and dateval <= '2007-01-02 23:59:59';
+
+drop table t1;
+
 # End of 5.0 tests

sql/field.cc

@@ -5259,6 +5259,9 @@ void Field_date::sql_type(String &res) const
     1  Value was cut during conversion
     2  Wrong date string
     3  Datetime value that was cut (warning level NOTE)
+       This is used by opt_range.cc:get_mm_leaf(). Note that there is a
+       nearly-identical class Field_date doesn't ever return 3 from its
+       store function.
 */
 
 int Field_newdate::store(const char *from,uint len,CHARSET_INFO *cs)

sql/opt_range.cc

@@ -4414,6 +4414,7 @@ get_mm_leaf(PARAM *param, COND *conf_func, Field *field, KEY_PART *key_part,
     {
       tree= new (alloc) SEL_ARG(field, 0, 0);
       tree->type= SEL_ARG::IMPOSSIBLE;
+      goto end;
     }
     else
     {
@@ -4422,8 +4423,32 @@ get_mm_leaf(PARAM *param, COND *conf_func, Field *field, KEY_PART *key_part,
         for the cases like int_field > 999999999999999999999999 as well.
       */
       tree= 0;
+      if (err == 3 && field->type() == FIELD_TYPE_DATE && 
+          (type == Item_func::GT_FUNC || type == Item_func::GE_FUNC || 
+           type == Item_func::LT_FUNC || type == Item_func::LE_FUNC) )
+      {
+        /*
+          We were saving DATETIME into a DATE column, the conversion went ok
+          but a non-zero time part was cut off.
+
+          In MySQL's SQL dialect, DATE and DATETIME are compared as datetime
+          values. Index over a DATE column uses DATE comparison. Changing 
+          from one comparison to the other is possible:
+
+          datetime(date_col)< '2007-12-10 12:34:55' -> date_col<='2007-12-10'
+          datetime(date_col)<='2007-12-10 12:34:55' -> date_col<='2007-12-10'
+
+          datetime(date_col)> '2007-12-10 12:34:55' -> date_col>='2007-12-10'
+          datetime(date_col)>='2007-12-10 12:34:55' -> date_col>='2007-12-10'
+
+          but we'll need to convert '>' to '>=' and '<' to '<='. This will
+          be done together with other types at the end of this function
+          (grep for field_is_equal_to_item)
+        */
+      }
+      else
+        goto end;
     }
-    goto end;
   } 
   if (err < 0)
   {