MySQL KEY Partitioning

This is similar to hash partitioning, but it uses MySQL's internal hashing

function on the partitioning key. This is useful when you're unsure about the

distribution of data and want MySQL to handle it for you.

Example and Impact on Performance:

Consider a table that stores log entries identified by a UUID. In this case, the

UUIDs are randomly distributed. By using KEY partitioning, MySQL will ensure

an even distribution of data across all partitions, which can enhance query

performance.

To implement key partitioning, you can use the following syntax:

```sql

CREATE TABLE logs (

log_id UUID NOT NULL,

entry VARCHAR(1000),

created_at TIMESTAMP

)

PARTITION BY KEY(log_id)

PARTITIONS 4;

```

This will create 4 partitions and distribute the data evenly among them using

MySQL's internal hashing function on the UUID.

Transitioning between different partition types can be done using the `ALTER

TABLE` statement. For instance, to change a table partitioned by RANGE to

HASH partitioning, you would use a command like this:

```sql

ALTER TABLE orders

PARTITION BY HASH( YEAR(order_date) )

PARTITIONS 4;

```