POSTGRES - Quais os SQLs que estão demorando mais tempo para serem executados neste momento?

SELECT datname, usename, now()-query_start as tempo_execucao, waiting, client_addr, current_query FROM pg_stat_activity WHERE current_query <> ''order by 3 desc;


Versões de Postgres 9:
SELECT datname, usename, now()-query_start as tempo_execucao, waiting, client_addr, query FROM pg_stat_activity WHERE query <> ''order by 3 desc;