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How is a partitioning key used in MySQL?
KEY is used rather than HASH . KEY takes only a list of zero or more column names. Any columns used as the partitioning key must comprise part or all of the table’s primary key, if the table has one. Where no column name is specified as the partitioning key, the table’s primary key is used, if there is one.
Can a table be partitioned with both unique keys?
The following table cannot be partitioned at all, because there is no way to include in a partitioning key any columns that belong to both unique keys: CREATE TABLE t4 ( col1 INT NOT NULL, col2 INT NOT NULL, col3 INT NOT NULL, col4 INT NOT NULL, UNIQUE KEY (col1, col3), UNIQUE KEY (col2, col4) );
How is a NDB table partitioned in MySQL?
Tables using the NDB storage engine are implicitly partitioned by KEY, using the table’s primary key as the partitioning key (as with other MySQL storage engines).
The rule governing this relationship can be expressed as follows: All columns used in the partitioning expression for a partitioned table must be part of every unique key that the table may have. In other words, every unique key on the table must use every column in the table’s partitioning expression .
Is there global index for partitioned table in MySQL?
There is no “global” index for a partitioned table in MySQL. The only indexes you can put on a partitioned table ends up being separate indexes on each partition. Each partition is effectively an independent table. HASH partitioning is virtually useless; do you have a particular use for which you think it might be beneficial?
When does a partitioning key include a unique key?
Since every primary key is by definition a unique key, this restriction also includes the table’s primary key, if it has one. For example, the next two statements are invalid: In both cases, the primary key does not include all columns referenced in the partitioning expression.