Specifies values for query options that control the runtime behavior of other statements within the same session.
SET with no arguments returns a result set consisting of all available query options and their current values.
The query option name and any string argument values are case-insensitive.
Each query option has a specific allowed notation for its arguments. Boolean options can be enabled and disabled by assigning values of either true and false, or 1 and 0. Some numeric options accept a final character signifying the unit, such as 2g for 2 gigabytes or 100m for 100 megabytes. See Query Options for the SET Statement for the details of each query option.
MEM_LIMIT is probably the most commonly used query option. You can specify a high value to allow a resource-intensive query to complete. For testing how queries would work on memory-constrained systems, you might specify an artificially low value.
The following example sets some numeric and some Boolean query options to control usage of memory, disk space, and timeout periods, then runs a query whose success could depend on the options in effect:
set mem_limit=64g; set DISABLE_UNSAFE_SPILLS=true; set parquet_file_size=400m; set RESERVATION_REQUEST_TIMEOUT=900000; insert overwrite parquet_table select c1, c2, count(c3) from text_table group by c1, c2, c3;
Added in: CDH 5.2.0 (Impala 2.0.0)
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.
Cancellation: Cannot be cancelled.
HDFS permissions: This statement does not touch any HDFS files or directories, therefore no HDFS permissions are required.
See Query Options for the SET Statement for the query options you can adjust using this statement.