What is the difference between mysql drop partition and truncate partition - mysql

Question

Can someone explain the difference between below commands?
ALTER TABLE A DROP PARTITION p0;
and
ALTER TABLE A TRUNCATE PARTITION p0;
In which scenarios should we use DROP/TRUNCATE partition?

Answer 1

Both throw the data away. And it is not 'transactional', so you cannot recover the data with a ROLLBACK.
DROP PARTITION also removes the partition from the list of partitions.
TRUNCATE PARTITION leaves the partition in place, but empty.
A common usage of DROP PARTITION is to remove "old" rows. Think of a table of of information that needs to be kept for only 90 days. Use PARTITION BY RANGE(TO_DAYS(...)) and have weekly partitions. Then, every week DROP the oldest and ADD a new partition. More discussion here.
I have not seen a need for TRUNCATE.
Be aware that there are very few use cases where you can get any benefit from PARTITIONing. So far, I have found uses only for PARTITION BY RANGE.

Answer 2

TRUNCATING a partition will be good choice when you have LIST partitions on the table.
It will remove all rows which are part of LIST partition but will not remove the partition entry from the table structure.

Answer 3

Take a scenario where you want to store credit card transactions/orders placed etc., in a MySQL table. Since the data volume is huge, you might want to partition it. Say you have partitioned the table based on the month of transaction.
PARTITION BY RANGE ( month(transactionDate))
(PARTITION p0 VALUES LESS THAN (2) ENGINE = InnoDB,
PARTITION p1 VALUES LESS THAN (3) ENGINE = InnoDB,
PARTITION p2 VALUES LESS THAN (4) ENGINE = InnoDB,
PARTITION p3 VALUES LESS THAN (5) ENGINE = InnoDB,
PARTITION p4 VALUES LESS THAN (6) ENGINE = InnoDB,
PARTITION p5 VALUES LESS THAN (7) ENGINE = InnoDB,
PARTITION p6 VALUES LESS THAN (8) ENGINE = InnoDB,
PARTITION p7 VALUES LESS THAN (9) ENGINE = InnoDB,
PARTITION p8 VALUES LESS THAN (10) ENGINE = InnoDB,
PARTITION p9 VALUES LESS THAN (11) ENGINE = InnoDB,
PARTITION p10 VALUES LESS THAN (12) ENGINE = InnoDB,
PARTITION p11 VALUES LESS THAN (13) ENGINE = InnoDB,
PARTITION p12 VALUES LESS THAN MAXVALUE ENGINE = InnoDB) */ |
You can also do it week wise if your data volume is huge.
Now you have to clean the old data from time to time. This is where the difference between Drop and Truncate comes. The list of partitions you have initially is p0,p1...p12.
When you drop a partition p1, the list becomes p0,p2,p3,p4...p12. So effectively the data for both Feb and March would go into p2.
But when you do a truncate, p1 is still intact but the data is evicted. So the list remains p0,p1...p12.