Bug#47925: regression of range optimizer and date comparison in 5.1.39!

When a query was using a DATE or DATETIME value formatted
using any other separator characters beside hyphen '-', a
query with a greater-or-equal '>=' condition matching only
the greatest value in an indexed column, the result was
empty if index range scan was employed.

The range optimizer got a new feature between 5.1.38 and
5.1.39 that changes a greater-or-equal condition to a
greater-than if the value matching that in the query was not
present in the table. But the value comparison function
compared the dates as strings instead of dates.

The bug was fixed by splitting the function
get_date_from_str in two: One part that parses and does
error checking. This function is now visible outside the
module. The old get_date_from_str now calls the new
function.

1 files changed, 9 insertions, 7 deletions

diff --git a/sql/time.cc b/sql/time.cc
index 962b65e454c..8b554beb94b 100644
--- a/sql/time.cc
+++ b/sql/time.cc
@@ -965,20 +965,22 @@ calc_time_diff(MYSQL_TIME *l_time1, MYSQL_TIME *l_time2, int l_sign, longlong *s
     0   - a == b
     1   - a > b
 
-  NOTES
-    TIME.second_part is not considered during comparison
 */
 
-int
-my_time_compare(MYSQL_TIME *a, MYSQL_TIME *b)
+int my_time_compare(MYSQL_TIME *a, MYSQL_TIME *b)
 {
-  my_ulonglong a_t= TIME_to_ulonglong_datetime(a);
-  my_ulonglong b_t= TIME_to_ulonglong_datetime(b);
+  ulonglong a_t= TIME_to_ulonglong_datetime(a);
+  ulonglong b_t= TIME_to_ulonglong_datetime(b);
 
+  if (a_t < b_t)
+    return -1;
   if (a_t > b_t)
     return 1;
-  else if (a_t < b_t)
+
+  if (a->second_part < b->second_part)
     return -1;
+  if (a->second_part > b->second_part)
+    return 1;
 
   return 0;
 }