This section discusses limitations in MySQL Partitioning relating specifically to functions used in partitioning expressions.
Only the MySQL functions shown in the following table are allowed in partitioning expressions.
ABS() | CEILING() (see
CEILING() and FLOOR()) | DAY() |
DAYOFMONTH() | DAYOFWEEK() | DAYOFYEAR() |
DATEDIFF() | EXTRACT() (see
EXTRACT() function with WEEK specifier) | FLOOR() (see
CEILING() and FLOOR()) |
HOUR() | MICROSECOND() | MINUTE() |
MOD() | MONTH() | QUARTER() |
SECOND() | TIME_TO_SEC() | TO_DAYS() |
TO_SECONDS() (implemented in MySQL 5.5.0) | UNIX_TIMESTAMP() (permitted beginning
with MySQL 5.5.1 and fully supported beginning with
MySQL 5.5.15, with
TIMESTAMP columns) | WEEKDAY() |
YEAR() | YEARWEEK() |
In MySQL 5.5, range optimization can be used for
the TO_DAYS(),
TO_SECONDS(), and
YEAR() functions. In addition,
beginning with MySQL 5.5.15,
UNIX_TIMESTAMP() is treated as
monotonic in partitioning expressions. See
Section 19.4, “Partition Pruning”, for more information.
CEILING() and FLOOR().
Each of these functions returns an integer only if it is
passed an argument of an exact numeric type, such as one of
the INT types or
DECIMAL. This means, for
example, that the following CREATE
TABLE statement fails with an error, as shown here:
mysql>CREATE TABLE t (c FLOAT) PARTITION BY LIST( FLOOR(c) )(->PARTITION p0 VALUES IN (1,3,5),->PARTITION p1 VALUES IN (2,4,6)->);ERROR 1490 (HY000): The PARTITION function returns the wrong type
EXTRACT() function with WEEK specifier.
The value returned by the
EXTRACT() function, when used
as EXTRACT(WEEK FROM
, depends on the
value of the
col)default_week_format system
variable. For this reason, beginning with MySQL 5.5.9,
EXTRACT() is no longer
permitted as a partitioning function when it specifies the
unit as WEEK. (Bug #54483)
See Section 12.6.2, “Mathematical Functions”, for more information about the return types of these functions, as well as Section 11.2, “Numeric Types”.