PostgreSQL Manual
This manual is provided as a courtesy. It is not an official source. Please check postgresql.org for updated information.
To close a connection, use the following statement:
EXEC SQL DISCONNECT [connection];
The connection can be specified in the following ways:
connection-name
DEFAULT
CURRENT
ALL
If no connection name is specified, the current connection is closed.
It is good style that an application always explicitly disconnect from every connection it opened.