MySQL table partition by month

Question

I have a huge table that stores many tracked events, such as a user click.

The table is already in the 10\'s of millions, and its growing larger everyday. The querie

Answer 1

CREATE TABLE `mytable` (
  `post_id` int DEFAULT NULL,
  `viewid` int DEFAULT NULL,
  `user_id` int DEFAULT NULL,
  `post_Date` datetime DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
PARTITION BY RANGE (extract(year_month from `post_Date`))
(PARTITION P0 VALUES LESS THAN (202012) ENGINE = InnoDB,
 PARTITION P1 VALUES LESS THAN (202104) ENGINE = InnoDB,
 PARTITION P2 VALUES LESS THAN (202108) ENGINE = InnoDB,
 PARTITION P3 VALUES LESS THAN (202112) ENGINE = InnoDB,
 PARTITION P4 VALUES LESS THAN MAXVALUE ENGINE = InnoDB)

Answer 2

HASHing by month with 6 partitions means that two months a year will land in the same partition. What good is that?

Don't bother partitioning, index the table.

Assuming these are the only two queries you use:

SELECT * from ti;
SELECT * from ti PARTITION (HASH(MONTH(some_date)));

then start the PRIMARY KEY with the_date.

The first query simply reads the entire table; no change between partitioned and not.

The second query, assuming you want a single month, not all the months that map into the same partition, would need to be

SELECT * FROM ti  WHERE the_date >= '2019-03-01'
                    AND the_date  < '2019-03-01' + INTERVAL 1 MONTH;

If you have other queries, let's see them.

(I have not found any performance justification for ever using PARTITION BY HASH.)

Answer 3

As explained by the manual: http://dev.mysql.com/doc/refman/5.6/en/partitioning-overview.html

This is easily possible by hash partitioning of the month output.

CREATE TABLE ti (id INT, amount DECIMAL(7,2), tr_date DATE)
    ENGINE=INNODB
    PARTITION BY HASH( MONTH(tr_date) )
    PARTITIONS 6;

Do note that this only partitions by month and not by year, also there are only 6 partitions (so 6 monhts) in this example.

And for partitioning an existing table (manual: https://dev.mysql.com/doc/refman/5.7/en/alter-table-partition-operations.html):

ALTER TABLE ti
    PARTITION BY HASH( MONTH(tr_date) )
    PARTITIONS 6;

Querying can be done both from the entire table:

SELECT * from ti;

Or from specific partitions:

SELECT * from ti PARTITION (HASH(MONTH(some_date)));

Answer 4

Use TokuDb which has an access time independent of the table size.