Change compactor configuration for Hive Virtual Warehouses
To enhance performance, the compactor is a set of background processes that compact delta files, which are created as a by-product of data modifications. When it runs, it incurs additional load on the Hive Virtual Warehouse assigned as the compactor in Cloudera Data Warehouse (CDW) Public Cloud. You can change which Hive warehouse performs compaction to load-balance this workload as necessary.
In CDW Public Cloud, data compaction is performed on HiveServer2, which equates to the Hive Virtual Warehouse construct in the UI. This means that compaction is essentially query execution. Compaction runs an INSERT statement created from the output of a SELECT statement and runs in the Hive Virtual Warehouse assigned as the compactor, thereby re-writing the data. The Hive Virtual Warehouse, configured as the compactor, delivers the query capacity to perform this. Therefore, when you size the Hive Virtual Warehouse that performs compaction, you must take into consideration the extra workload to run the compaction queries. That extra workload needs to be considered in addition to your other query workloads on the Hive Virtual Warehouse that is configured as the compactor.
One of the Hive Virtual Warehouses must be configured as the compactor for the associated Database Catalog. This Hive Virtual Warehouse compactor runs all of the compaction queries for all Virtual Warehouses that use one particular Database Catalog, including Impala Virtual Warehouses. However, Impala Virtual Warehouses cannot be configured as the compactor Virtual Warehouse for a Database Catalog. Compaction tasks must be assigned to a Hive Virtual Warehouse. The first Hive Virtual Warehouse you create against a Database Catalog is automatically set as the compactor. If you decide you do not want that particular warehouse to take on the compaction workload, you can set another Hive Virtual Warehouse to perform the compaction workload by following these steps:
- Log in to the CDP web interface and navigate to the Data Warehouse service.
- On the Overview page, select the Hive Virtual Warehouse that you want to set as the compactor, and click the options menu .
- In the options menu, select Set Compactor.