WLM queue assignment rules - Amazon Redshift
Queue assignments example

WLM queue assignment rules

With Amazon Redshift, you can control the allocation of memory and CPU resources to user queries by defining queue assignment rules in a workload management (WLM) configuration. The following section describes creating and managing WLM queue assignment rules to achieve efficient resource allocation and meet service-level agreements for diverse workloads in Amazon Redshift.

When a user runs a query, WLM assigns the query to the first matching queue, based on the WLM queue assignment rules:

  1. If a user is logged in as a superuser and runs a query in the query group labeled superuser, the query is assigned to the superuser queue.

  2. If a user is part of a role, belongs to a listed user group, or runs a query within a listed query group, the query is assigned to the first matching queue.

  3. If a query doesn't meet any criteria, the query is assigned to the default queue, which is the last queue defined in the WLM configuration.

The following diagram illustrates how these rules work.

Flowchart illustrating the rules WLM uses to assign queries to queues.

Queue assignments example

The following table shows a WLM configuration with the superuser queue and four user-defined queues.

Queue Concurrency User Roles User Groups Query Groups

Superuser

1

superuser

1

5

test_db_rw

UG_1

2

5

QG_B

3

5

UG_2

QG_C

Default

5

The following illustration shows how queries are assigned to the queues in the previous table according to user groups and query groups. For information about how to assign queries to user groups and query groups at runtime, see Assigning queries to queues later in this section.

Sample list of queries assigned to queues according to user groups and query groups.

In this example, WLM makes the following assignments:

  1. The first set of statements shows three ways to assign users to user groups. The statements are run by the user adminuser, which is not a member of a user group listed in any WLM queue. No query group is set, so the statements are routed to the default queue.

  2. The user adminuser is a superuser and the query group is set to 'superuser', so the query is assigned to the superuser queue.

  3. The user test_user is assigned the role test_db_rw listed in queue 1, so the query is assigned to queue 1.

  4. The user admin1 is a member of the user group listed in queue 1, so the query is assigned to queue 1.

  5. The user vp1 is not a member of any listed user group. The query group is set to 'QG_B', so the query is assigned to queue 2.

  6. The user analyst1 is a member of the user group listed in queue 3, but 'QG_B' matches queue 2, so the query is assigned to queue 2.

  7. The user ralph is not a member of any listed user group and the query group was reset, so there is no matching queue. The query is assigned to the default queue.