get postgreSQL client computer name
Yes.

select * 
from pg_stat_activity 
where pid = pg_backend_pid();


client_hostname And client_addr are relevant.

log_hostname needs enabling in order for the name to be resolved correctly. See this link:


  By default, connection log messages only show the IP address of the
  connecting host. Turning this parameter on causes logging of the host
  name as well. Note that depending on your host name resolution setup
  this might impose a non-negligible performance penalty. This parameter
  can only be set in the postgresql.conf file or on the server command
  line.