pg_conndefaults Returning empty string

Hi,

I am accessing postgres database using tcl. I am looking for a way to
change the database in an existing connection, but I saw that this is not
possible in postgresql without creating a new connection.

Then I decided to query pg_conndefaults so that I can get the previous
connection detail, mainly the host ip address. But
it returned blank strings. Is there a way to set the pg_conndefault
values.Then I can use those values to make the new connection. Please
understand that at this point in the code, I have no information about the
previous connection parameters. I only know the new database name to which
it has to be connected.

Please let me know if there is a way to tackle this situation.

Thank You
Anushka