Improvements to Trac's data models
Trac's datamodels are usually implemented in the
In the current situation (1.0.x/1.1.1), we have different APIs and different conventions for the datamodels. This page describes a few issues where the API and conventions can be improved and made more consistent.
Representation of data
Standardize missing values
For tickets, when a field is unset the database value is set to
NULL (#11018). When retrieving
NULL values from the database, we get
None in Python, and the value returned from the model depends on the field type:
- For text fields, the empty string is returned from the model using the special value empty. See for example what we do for ticket fields.
- For time fields,
The pattern could be extended to other model classes, and even the
Ticket model should be reviewed to ensure that all fields follow the pattern.
NOT NULL columns
Validation of the ticket summary is done in the IRequestHandler, to prevent creating a ticket with an empty summary. The schema could be changed to use
NOT NULL in the column specification, since the empty string is replaced with NULL. Alternatively, a
TracError could be raised in the
Ticket model when
updateing a ticket with an empty summary (#12458).
Class methods are used for table-wide queries. One such example is
The signature of the
select method is not consistent across all classes.
Milestone class has an include_completed parameter in the
We could reconcile the inconsistency by having
order_by parameters on each method, with the parameters directly mapping to phrases in the SQL query.
This would make the methods more generally useful to plugin developers.
Not only is the interface inconsistent, but also the return value. In most cases a generator is returned by
select, however some
select methods return a list: