UR::Manual::SchemaDesign(3) Tips for designing an efficient schema for UR

Relational Databases

Avoid creating a table called 'type' or 'types'.
When 'ur update classes' translates it into a class name, it will become YourNamespace::Type. Class names ending in '::Type' are reserved for class metadata, the class will be renamed to 'YourNamespace::TypeTable' to avoid the conflict. The table_name for that class will still refer to the actual table name. 'ur update classes' will print a warning if this happens, and rename the class automatically.
Avoid columns named 'id'
UR expects an object to be uniquely identified by a property called 'id'. Classes cannot have multiple ID properties where one of them is called 'id', because 'id' would no uniqiely identify one of them. If you want to call the column 'id', then the property name in the class metadata must be something else ('id_id', for example) in both the 'has' and 'id_by' sections, and the column_name set to 'id'.
Indexes for common queries
Create indexes in your database to cover common queries. If you routinely make queries involving non-primary keys, creating an index that includes these other columns will improve query times.