Apache Impala SQL ReferencePDF version

SET statement

The SET statement specifies values for query options that control the runtime behavior of other statements within the same session.

When issued in impala-shell, the SET command is interpreted as an impala-shell command that has differences from the SQL SET statement.

Syntax: 

SET
SET ALL
SET query_option=option_value
SET query_option=""

SET and SET ALL with no arguments return a result set consisting of all the applicable query options and their current values.

The query_option and option_value are case-insensitive.

Unlike the impala-shell command version of SET, when used as a SQL statement, the string values for option_value need to be quoted, e.g. SET option="new_value".

The SET query_option = "" statement unsets the value of the query_option in the current session, reverting it to the default state. In impala-shell, use the UNSET command to set a query option to its default.

Each query option has a specific allowed notation for its arguments. See Query options for the SET statement for the details of each query option.

Usage notes:

The options are divided into groups: Regular Query Options, Advanced Query Options, Development Query Options, and Deprecated Query Options.

  • The advanced options are intended for use in specific kinds of performance tuning and debugging scenarios.

  • The development options are related to internal development of Impala or features that are not yet finalized. These options might be changed or removed without notice.

  • The deprecated options are related to features that are removed or changed so that the options no longer have any purpose. These options might be removed in future versions.

  • By default, only the first two groups, regular and advanced, are displayed by the SET command. Use SET ALL to see all groups of options.

  • impala-shell options and user-specified variables are always displayed at the end of the list of query options, after all appropriate option groups.

SET has always been available as an impala-shell command. Promoting it to a SQL statement lets you use this feature in client applications through the JDBC and ODBC APIs.

HDFS permissions: This statement does not touch any HDFS files or directories, therefore no HDFS permissions are required.

Cloudera Manager: You can set any of the query options globally in Cloudera Manager to affect all the queries in the cluster.

  1. Navigate to Impala cluster > Configuration > Impala Daemon Query Options Advanced Configuration Snippet (Safety Valve)
  2. In the field, type a key-value pair of a query option and the value, e.g. EXPLAIN_LEVEL=2.
  3. Click + to enter an additional option.
  4. Clive Save Changes.