A common request on the PostgreSQL mailing lists is for users to provide a list of settings they've changed. This helps everyone diagnose where a problem could originate or give us an idea of a database's usage pattern. Now that we know about this view, we can easily provide that data with the following query:
SELECT name, setting FROM pg_settings WHERE boot_val IS DISTINCT FROM setting;
The IS DISTINCT FROM clause isn't as well known as it should be. It can be easy to forget that != or <> evaluates to NULL when either side of the equation is NULL. Thus, if the default boot_val value is NULL, we would fail to obtain the entire list of modified settings.
The IS DISTINCT FROM clause considers NULL as a distinct value instead ...
