LIVE_SUMMARY Query Option (Impala 2.3 or higher only)
LIVE_SUMMARY query option is set
TRUE, Impala displays the same output as the
SUMMARY command for queries submitted through the
impala-shell command, with the measurements updated
in real time as the query progresses. When the query finishes, the final
SUMMARY output remains visible in the
impala-shell console output.
Starting in Impala 3.1, the summary output also includes the queuing status consisting of whether the query was queued and what was the latest queuing reason.
You can enable this query option within impala-shell
by starting the shell with the
command-line option. You can still turn this setting off and on again
within the shell through the
The live summary output can be useful for evaluating long-running queries, to evaluate which phase of execution takes up the most time, or if some hosts take much longer than others for certain operations, dragging overall performance down. By making the information available in real time, this feature lets you decide what action to take even before you cancel a query that is taking much longer than normal.
For example, you might see the HDFS scan phase taking a long time, and
therefore revisit performance-related aspects of your schema design such
as constructing a partitioned table, switching to the Parquet file format,
COMPUTE STATS statement for the table, and so
on. Or you might see a wide variation between the average and maximum
times for all hosts to perform some phase of the query, and therefore
investigate if one particular host needed more memory or was experiencing
a network problem.
The output from this query option is printed to standard
error. The output is displayed only in interactive mode, not when the
-f options are used.
For a simple and concise way of tracking the progress of an interactive query, see LIVE_PROGRESS Query Option (Impala 2.3 or higher only).
LIVE_SUMMARY query options
currently do not produce any output during
COMPUTE STATS operations.
LIVE_SUMMARYquery options are available only within the impala-shell interpreter:
You cannot change these query options through the SQL
SETstatement using the JDBC or ODBC interfaces. The
SETcommand in impala-shell recognizes these names as shell-only options.
Be careful when using impala-shell on a pre-Impala 2.3 system to connect to a system running Impala 2.3 or higher. The older impala-shell does not recognize these query option names. Upgrade impala-shell on the systems where you intend to use these query options.
Likewise, the impala-shell command relies on some information only available in Impala 2.3 and higher to prepare live progress reports and query summaries. The
LIVE_SUMMARYquery options have no effect when impala-shell connects to a cluster running an older version of Impala.
Added in: Impala 2.3.0
To see how the
options work in real time, see