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

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