Manual:$wgDBtype/en

Details
Type of database.
 * "mssql" - MS-SQL
 * "mysql" -
 * "oracle" - (added in version 1.5)
 * "postgres" - (added in version 1.7)
 * "sqlite" - (added in version 1.13)

Older versions may have used "pgsql" or "PostgreSQL" instead of "postgres". The documentation was updated to use "postgres" in 1.8.0, but the switch may have been made earlier.