[drupal-support] Fatal error: Call to undefined function: pg_connect()

[emdeex]

I've just had a server restored and now my drupal database is giving
this error when I try to access the site:

Fatal error: Call to undefined function: pg_connect() in
/home/stonetil/public_html/includes/database.pgsql.inc on line 28

I see that this is a PostgreSQL database connection routine, but I
don't have postgresql installed.  Ive always used MySQL.

Why is drupal calling this routine, and how can I make it go back to
using MySQL?

The include database.inc seems to indicate that Drupal is looking to
set an active database, why?  Can I override it?

thanks
emdee