![[Note]](../common/images/admon/note.png) | Note |
|---|---|
This feature is a technical preview and considered under development. Do not use this feature in your production systems. If you have questions regarding this feature, contact Support by logging a case on our Hortonworks Support Portal at http://support.hortonworks.com. |
Hive 0.13.0 introduces Cost-based optimization of SQL queries. Cost-based optimization may reduce query latency by reducing the cardinality of the intermediate result set. The Cost-based Optimizer improves usability because it removes the need for query hints for good query execution plans. The Cost-based Optimizer is useful in the following scenarios:
Ad hoc queries containing multiple views
View chaining
Business Intelligence tools that act as a front end to Hive
Enabling Cost-based Optimzation
Set the following configuration parameters in hive-site.xml to
enable cost-based optimization of SQL:
Table 2.1. CBO Configuration Parameters
| Configuration Parameter | Description | Default Value |
|---|---|---|
hive.cbo.enable | Indicates whether to use cost-based query optimization. | false |
hive.cbo.max.joins.supported | Specifies the maximum number of joins that may be included in a query that is submitted for cost-based optimization. | 10 |
