distribution_style

Usage

view: my_view {
  derived_table: {
    distribution_style: all
    ...
  }
}

Definition

distribution_style lets you specify how the query for a persistent derived table (PDT) or an aggregate table is distributed across the nodes in a database.

See the Dialect support for distribution_style section below for the list of dialects that support distribution_style.

The distribution_style parameter works only with tables that are persistent, such as PDTs and aggregate tables. distribution_style is not supported for derived tables without a persistence strategy.

In addition, the distribution_style parameter is not supported for derived tables that are defined using create_process or sql_create.

Lastly, distribution_style and distribution should not be used at the same time. If you want to distribute the rows of a table to different Redshift nodes based on a column value, use distribution. Otherwise, use distribution_style to choose a different distribution strategy.

Redshift offers four distribution styles, which are described in their documentation:

• ALL Distribution: All rows are fully copied to each node. You can accomplish this type of distribution in Looker by using distribution_style: all.
• EVEN Distribution: Rows are distributed to different nodes in a round-robin fashion. You can accomplish this type of distribution in Looker by using distribution_style: even.
• KEY Distribution: Rows are distributed to different nodes based on unique values within a particular column. You can accomplish this type of distribution in Looker by using the distribution parameter.
• AUTO Distribution Redshift assigns an optimal distribution style based on the size of the table data. Looker does not currently support this distribution type.

See the Amazon Redshift documentation for choosing the appropriate distribution strategy. If you do not specify a distribution_style, and do not use the distribution parameter instead, Looker will default to all.

Examples

Create a customer_order_facts derived table with a distribution style of all:

view: customer_order_facts {
  derived_table: {
    sql:
      SELECT
        customer_id,
        COUNT(*) AS lifetime_orders
      FROM
        order
      GROUP BY 1 ;;
    persist_for: "24 hours"
    distribution_style: all
  }
}

Dialect support for distribution_style

The ability to use distribution_style depends on the database dialect your Looker connection is using. In the latest release of Looker, the following dialects support distribution_style: