> If i do a explain select partitions i got just one partition on the result.
That does _not_ mean that it is any faster than if you did not have partitioning.
SELECT (ddl_ct2 + 128)
FROM gps_data
WHERE COORDINATE_DATE between SUBDATE(#currentCoordinateDate#, 2)
AND #currentCoordinateDate#
AND `MONTH`= MONTH(#currentCoordinateDate#)
AND (ddl_ten + 128) * 0.5 > 8
AND vei_id = #vehicleID#
ORDER BY ddl_dh DESC
LIMIT 5
will probably use the first two fields of
KEY `IDX_DDL_PTP_IDR` (`VEI_ID`,`COORDINATE_DATE `,`PTP_IDR`),
Is that what the EXPLAIN says?
Yes, adding MONTH to the WHERE clause made the query about 12 times as fast. But now it is about as fast as if the table were not partitioned.