Remove SetId() call from *Read(), this isn't required for import to work.

builtin/providers/postgresql/resource_postgresql_database.go

@@ -324,7 +324,6 @@ func resourcePostgreSQLDatabaseRead(d *schema.ResourceData, meta interface{}) er
 			dbTemplate = "template0"
 		}
 		d.Set(dbTemplateAttr, dbTemplate)
-		d.SetId(dbName)
 		return nil
 	}
 }