Hi Alina,
you can specify query options by appending them to the connection string for the JDBC driver, separated by semicolon. For example
jdbc:impala://me.cloudera.com:21050/default;appx_count_distinct=1
Settings you add there will be active for all queries during that JDBC connection. If you want to change defaults for the impalad daemon lifetime you can do so by adjusting IMPALA_SERVER_ARGS as described here: http://www.cloudera.com/documentation/enterprise/5-4-x/topics/impala_config_options.html
Cheers, Lars