Enabling the Calcite planner [Preview]

Enable the Apache Calcite planner for a session by setting the PLANNER query option, so that Impala compiles queries with cost-based optimization.

The Calcite planner is disabled by default. Set the PLANNER query option to CALCITE to enable it for the current session.

Set the PLANNER query option to CALCITE.
```
SET PLANNER=CALCITE;
```
Optional: Set the FALLBACK_PLANNER query option to specify the planner Impala uses if the Calcite planner fails to compile a query.
```
SET FALLBACK_PLANNER=ORIGINAL;
```
Run your query.
You can also set the query option globally for all queries by configuring the default query options property in Cloudera Manager.
1. Go to Clusters > Impala > Configuration.
2. Search for Default Query Options.
3. Enter the query option and value by using the following format:
```
OPTION_NAME=VALUE
```
  For multiple options, separate each key-value pair with a comma.
4. Save the changes.
5. Restart the Impala service to apply the updated configuration.
Impala compiles the query with the Calcite planner. If compilation fails and a different fallback planner is set, Impala compiles the query with the fallback planner.

The session uses the Calcite planner for subsequent queries until you change the PLANNER query option.