current_timestamp returns the current date and time in the
session time zone, in a value of datatype TIMESTAMP WITH TIME ZONE. The
time zone displacement reflects the current local time of the SQL
session. If you omit precision, then the default is 6. The difference
between this function and localtimestamp is that current_timestamp
returns a TIMESTAMP WITH TIME ZONE value while localtimestamp
returns a TIMESTAMP value. In the optional argument, precision specifies
the fractional second precision of the time value returned.