ALTER RESOURCE GROUP
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ALTER RESOURCE GROUP
Changes the limits of a resource group.
ALTER RESOURCE GROUP name SET group_attribute value
where group_attribute is one of:
CONCURRENCY integer CPU_RATE_LIMIT integer CPUSET tuple MEMORY_LIMIT integer MEMORY_SHARED_QUOTA integer MEMORY_SPILL_RATIO integer
ALTER RESOURCE GROUP changes the limits of a resource group. Only a superuser can alter a resource group.
You can set or reset the concurrency limit of a resource group that you create for roles to control the maximum number of active concurrent statements in that group. You can also reset the memory or CPU resources of a resource group to control the amount of memory or CPU resources that all queries submitted through the group can consume on each segment host.
When you alter the CPU resource management mode or limit of a resource group, the new mode or limit is immediately applied.
When you alter a memory limit of a resource group that you create for roles, the new resource limit is immediately applied if current resource usage is less than or equal to the new value and there are no running transactions in the resource group. If the current resource usage exceeds the new memory limit value, or if there are running transactions in other resource groups that hold some of the resource, then Greenplum Database defers assigning the new limit until resource usage falls within the range of the new value.
When you increase the memory limit of a resource group that you create for external components, the new resource limit is phased in as system memory resources become available. If you decrease the memory limit of a resource group that you create for external components, the behavior is component-specific. For example, if you decrease the memory limit of a resource group that you create for a PL/Container runtime, queries in a running container may fail with an out of memory error.
You can alter one limit type in a single ALTER RESOURCE GROUP call.
- The name of the resource group to alter.
- CONCURRENCY integer
- The maximum number of concurrent transactions, including active and idle transactions, that are permitted for resource groups that you assign to roles. Any transactions submitted after the CONCURRENCY value limit is reached are queued. When a running transaction completes, the earliest queued transaction is executed.
- The CONCURRENCY value must be an integer in the range [0 .. max_connections]. The default CONCURRENCY value for a resource group that you create for roles is 20.
Note: You cannot set the CONCURRENCY value for the admin_group to zero (0).
- CPU_RATE_LIMIT integer
- The percentage of CPU resources to allocate to this resource group. The minimum CPU percentage for a resource group is 1. The maximum is 100. The sum of the CPU_RATE_LIMITs of all resource groups defined in the Greenplum Database cluster must not exceed 100.
- If you alter the CPU_RATE_LIMIT of a resource group in which you previously configured a CPUSET, CPUSET is disabled, the reserved CPU cores are returned to Greenplum Database, and CPUSET is set to -1.
- CPUSET tuple
- The CPU cores to reserve for this resource group. The CPU cores that you specify in tuple must be available in the system and cannot overlap with any CPU cores that you specify for other resource groups.
- tuple is a comma-separated list of single core numbers or core intervals. You must enclose tuple in single quotes, for example, '1,3-4'.
- If you alter the CPUSET value of a resource group for which you previously configured a CPU_RATE_LIMIT, CPU_RATE_LIMIT is disabled, the reserved CPU resources are returned to Greenplum Database, and CPU_RATE_LIMIT is set to -1.
- You can alter CPUSET for a resource group only after you have enabled resource group-based resource management for your Greenplum Database cluster.
- MEMORY_LIMIT integer
- The percentage of memory resources to allocate to this resource group. The minimum memory percentage for a resource group is 1. The maximum is 100. The sum of the MEMORY_LIMITs of all resource groups defined in the Greenplum Database cluster must not exceed 100.
- MEMORY_SHARED_QUOTA integer
- The percentage of memory resources to share among transactions in the resource group. The minimum memory shared quota percentage for a resource group is 0. The maximum is 100. The default MEMORY_SHARED_QUOTA value is 20.
- MEMORY_SPILL_RATIO integer
- The memory usage threshold for memory-intensive operators in a transaction issued in the resource group. The minimum memory spill ratio percentage for a resource group is 0. The maximum is 100. The default MEMORY_SPILL_RATIO value is 20.
You cannot submit an ALTER RESOURCE GROUP command in an explicit transaction or sub-transaction.
Change the active transaction limit for a resource group:
ALTER RESOURCE GROUP rgroup1 SET CONCURRENCY 13;
Update the CPU limit for a resource group:
ALTER RESOURCE GROUP rgroup2 SET CPU_RATE_LIMIT 45;
Update the memory limit for a resource group:
ALTER RESOURCE GROUP rgroup3 SET MEMORY_LIMIT 30;
Increase the memory spill ratio for a resource group from the default:
ALTER RESOURCE GROUP rgroup4 SET MEMORY_SPILL_RATIO 25;
Reserve CPU core 1 for a resource group:
ALTER RESOURCE GROUP rgroup5 SET CPUSET '1';
The ALTER RESOURCE GROUP statement is a Greenplum Database extension. This command does not exist in standard PostgreSQL.