Greenplum Database, a Massively Parallel Processing Data Warehouse built ontop of the PostgreSQL technology, often has very large installations running millions of queries per day by hundreds or thousands of users in the user population. In order to maintain order in the environment, Database Administrators can rely on Resource Groups to provide concurrency flow control and resource allocation and management of competing users and workloads on the environment.
Resource Groups are a Greenplum native feature, not present in PostgreSQL. PostgreSQL is more suited to OLTP workloads and not long running queries and hence does not provide any resource management and queuing functionality.
The features of Resource Groups include Concurrency Control, CPU Control, Memory Control, Workload Isolation and dynamic bursting.
For more information about how to configure and optimize Resource Groups, please review the Practical Guide to Greenplum Database Resource Group Management and also the official documentation from VMware, both provide more in depth details.
Additionally you can review video tutorials on Resource Groups from the links below: