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Updated on 2023-10-23 GMT+08:00
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ALTER RESOURCE POOL

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Function

ALTER RESOURCE POOL changes the Cgroup of a resource pool.

Precautions

Only a user with the ALTER permission on the current database can perform this operation.

Syntax

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ALTER RESOURCE POOL pool_name
    WITH ({MEM_PERCENT= pct | CONTROL_GROUP="group_name" | ACTIVE_STATEMENTS=stmt | MAX_DOP = dop | MEMORY_LIMIT='memory_size' | io_limits=io_limits | io_priority='io_priority'}[, ... ]);

Parameter Description

  • pool_name

    Specifies the name of a resource pool.

    The resource pool must already exist.

    Value range: a string. It must comply with the naming convention.

  • group_name

    Specifies the name of a Cgroup.

    • You can use either double quotation marks ("") or single quotation marks ('') in the syntax when setting the name of a Cgroup.
    • The value of group_name is case-sensitive.
    • If group_name is not specified, the string "Medium" will be used by default in the syntax, indicating the Medium Timeshare Cgroup under DefaultClass.
    • If an administrator specifies a Workload Cgroup under Class, for example, control_group set to class1:workload1, the resource pool will be associated with the workload1 Cgroup under class1. The level of Workload can also be specified. For example, control_group is set to class1:workload1:1.
    • If a database user specifies the Timeshare string (Rush, High, Medium, or Low) in the syntax, for example, control_group is set to High, the resource pool will be associated with the High Timeshare Cgroup under DefaultClass.
    • In multi-tenant scenarios, the Cgroup associated with a group resource pool is a Class Cgroup, and that associated with a service resource pool is a Workload Cgroup. Additionally, switching Cgroups between different resource pools is not allowed.

    Value range: an existing Cgroup.

  • stmt

    Specifies the maximum number of statements that can be concurrently executed in a resource pool.

    Value range: numeric data ranging from –1 to 2147483647

  • dop

    Specifies the maximum statement concurrency degree for a resource pool, equivalent to the number of threads that can be created for executing a statement.

    Value range: numeric data ranging from 1 to 2147483647

  • memory_size

    Specifies the maximum memory size of a resource pool.

    Value range: a string from 1 KB to 2047 GB

  • mem_percent

    Specifies the proportion of available resource pool memory to the total memory or group user memory.

    In multi-tenant scenarios, mem_percent of group users or service users ranges from 1 to 100. The default value is 20.

    In common scenarios, mem_percent of common users is an integer ranging from 0 to 100. The default value is 0.

    When both of mem_percent and memory_limit are specified, only mem_percent takes effect.

  • io_limits

    Specifies the upper limit of IOPS in a resource pool.

    Row-store is measured by 10,000 IOPS, while column-store is measured by IOPS.

  • io_priority

    Specifies the I/O priority for jobs that consume many I/O resources. It takes effect when the I/O usage reaches 90%.

    There are three priorities: Low, Medium, and High. If you do not want to control I/O resources, set this parameter to None, which is the default value.

The settings of io_limits and io_priority are valid only for complex jobs, such as batch import (using INSERT INTO SELECT, COPY FROM, or CREATE TABLE AS), complex queries involving over 500 MB data on each DN, and VACUUM FULL.

Examples

The following example assumes that the user has created the class1 Cgroup and three Workload Cgroups under class1: Low, wg1, and wg2.

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-- Create a resource pool.
openGauss=# CREATE RESOURCE POOL pool1;

-- Specify the High Timeshare Workload Cgroup under the DefaultClass Cgroup.
openGauss=# ALTER RESOURCE POOL pool1 WITH (CONTROL_GROUP="High");

-- Specify the Low Timeshare Workload Cgroup under the class1 Cgroup.
openGauss=# ALTER RESOURCE POOL pool1 WITH (CONTROL_GROUP="class1:Low");

-- Specify the wg1 Workload Cgroup under the class1 Cgroup.
openGauss=# ALTER RESOURCE POOL pool1 WITH (CONTROL_GROUP="class1:wg1");

-- Specify the wg2 Workload Cgroup under the class1 Cgroup.
openGauss=# ALTER RESOURCE POOL pool1 WITH (CONTROL_GROUP="class1:wg2:3"); 
-- Delete the resource pool pool1.
openGauss=# DROP RESOURCE POOL pool1;

Helpful Links

CREATE RESOURCE POOL and DROP RESOURCE POOL

Parent topic: SQL Syntax