Manual:$wgDBmwschema

Details
Schema for mediawiki tables. Currently only used if your backend database is Postgres. This indicates what schema the main mediawiki tables live in, and is roughly equivalent to the way that $wgDBprefix is used by MySQL.

Warning: if you change this setting, you should probably create a new user (and change $wgDBuser as well), because the configuration script sets the user's default path to include the schema.