Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)

There were a problem since pruning uses the field
for comparison (while evaluate_join_record uses longlong),
resulting in pruning failures when comparing DATE to DATETIME.

Fix was to always comparing DATE vs DATETIME as DATETIME,
by adding ' 00:00:00' to the DATE string.

And adding optimization for comparing with 23:59:59, so that
DATETIME_col > '2001-02-03 23:59:59' ->
TO_DAYS(DATETIME_col) > TO_DAYS('2001-02-03 23:59:59') instead
of '>='.

mysql-test/r/partition_pruning.result:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  Updated result-file
mysql-test/t/partition_pruning.test:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  Added testcases.
sql-common/my_time.c:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  removed duplicate assignment.
sql/item.cc:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  Changed field_is_equal_to_item into field_cmp_to_item, to
  better handling DATE vs DATETIME comparision.
sql/item.h:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  Updated comment
sql/item_timefunc.cc:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  Added optimization (pruning) of DATETIME where time-part is
  23:59:59
sql/opt_range.cc:
  Bug#46362: Endpoint should be set to false for TO_DAYS(DATE)
  
  Using the new stored_field_cmp_to_item for better pruning.

1 files changed, 39 insertions, 11 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 2640b74851b..79ae4b20f30 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -6846,14 +6846,21 @@ void resolve_const_item(THD *thd, Item **ref, Item *comp_item)
 }
 
 /**
-  Return true if the value stored in the field is equal to the const
-  item.
+  Compare the value stored in field, with the original item.
 
-  We need to use this on the range optimizer because in some cases
-  we can't store the value in the field without some precision/character loss.
+  @param field   field which the item is converted and stored in
+  @param item    original item
+
+  @return Return an integer greater than, equal to, or less than 0 if
+          the value stored in the field is greater than,  equal to,
+          or less than the original item
+
+  @note We only use this on the range optimizer/partition pruning,
+        because in some cases we can't store the value in the field
+        without some precision/character loss.
 */
 
-bool field_is_equal_to_item(Field *field,Item *item)
+int stored_field_cmp_to_item(Field *field, Item *item)
 {
 
   Item_result res_type=item_cmp_type(field->result_type(),
@@ -6864,28 +6871,49 @@ bool field_is_equal_to_item(Field *field,Item *item)
     char field_buff[MAX_FIELD_WIDTH];
     String item_tmp(item_buff,sizeof(item_buff),&my_charset_bin),*item_result;
     String field_tmp(field_buff,sizeof(field_buff),&my_charset_bin);
+    enum_field_types field_type;
     item_result=item->val_str(&item_tmp);
     if (item->null_value)
-      return 1;					// This must be true
+      return 0;
     field->val_str(&field_tmp);
-    return !stringcmp(&field_tmp,item_result);
+
+    /*
+      If comparing DATE with DATETIME, append the time-part to the DATE.
+      So that the strings are equally formatted.
+      A DATE converted to string is 10 characters, and a DATETIME converted
+      to string is 19 characters.
+    */
+    field_type= field->type();
+    if (field_type == MYSQL_TYPE_DATE &&
+        item_result->length() == 19)
+      field_tmp.append(" 00:00:00");
+    else if (field_type == MYSQL_TYPE_DATETIME &&
+             item_result->length() == 10)
+      item_result->append(" 00:00:00");
+
+    return stringcmp(&field_tmp,item_result);
   }
   if (res_type == INT_RESULT)
-    return 1;					// Both where of type int
+    return 0;					// Both are of type int
   if (res_type == DECIMAL_RESULT)
   {
     my_decimal item_buf, *item_val,
                field_buf, *field_val;
     item_val= item->val_decimal(&item_buf);
     if (item->null_value)
-      return 1;					// This must be true
+      return 0;
     field_val= field->val_decimal(&field_buf);
-    return !my_decimal_cmp(item_val, field_val);
+    return my_decimal_cmp(item_val, field_val);
   }
   double result= item->val_real();
   if (item->null_value)
+    return 0;
+  double field_result= field->val_real();
+  if (field_result < result)
+    return -1;
+  else if (field_result > result)
     return 1;
-  return result == field->val_real();
+  return 0;
 }
 
 Item_cache* Item_cache::get_cache(const Item *item)