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Amazon Redshift
Database Developer Guide (API Version 2012-12-01)

Distribution Styles

When you create a table, you designate one of three distribution styles; EVEN, KEY, or ALL.

Even distribution

The leader node distributes the rows across the slices in a round-robin fashion, regardless of the values in any particular column. EVEN distribution is appropriate when a table does not participate in joins or when there is not a clear choice between KEY distribution and ALL distribution. EVEN distribution is the default distribution style.

Key distribution

The rows are distributed according to the values in one column. The leader node will attempt to place matching values on the same node slice. If you distribute a pair of tables on the joining keys, the leader node collocates the rows on the slices according to the values in the joining columns so that matching values from the common columns are physically stored together.

ALL distribution

A copy of the entire table is distributed to every node. Where EVEN distribution or KEY distribution place only a portion of a table's rows on each node, ALL distribution ensures that every row is collocated for every join that the table participates in.

ALL distribution multiplies the storage required by the number of nodes in the cluster, and so it takes much longer to load, update, or insert data into multiple tables. ALL distribution is appropriate only for relatively slow moving tables; that is, tables that are not updated frequently or extensively. Small dimension tables do not benefit significantly from ALL distribution, because the cost of redistribution is low.

Note

After you have specified a distribution style for a column, Amazon Redshift handles data distribution at the cluster level. Amazon Redshift does not require or support the concept of partitioning data within database objects. You do not need to create table spaces or define partitioning schemes for tables.