summaries : Summary tables

The lino.modlib.summaries plugin installs a framework for defining Summary fields and summary tables. A summary table is a table with summary fields.

A summary field is a readonly and otherwise regular database field whose value is computed at certain moments as a summary of other tables. This can be used as an alternative for virtual fields whose value is computed on the fly for each request.

The plugin has no models on its own but provides several model mixins and a checksummaries command which updates all summaries. It also schedules a daily linod task which does the same.

Users also get a button on each model for which there are slave summaries.

Usage examples

userstats: User statistics

Implementation of Summary Table

lino_xl.lib.tickets

Implementation of Summary fields.

European Social Fund

The most advanced use of summaries. Is a summary table used to calculate yearly and monthly worked time with clients based on meeting type and various other rules.

Summary fields

Another use of this module is to create summary fields.

Example: Client has two date fields active_from and active_until whose value is automatically computed based on all contracts with that client. They are not virtual fields because we want to sort and filter on them, and because their values aren't so very dynamic, they are the start and end date of the currently active contract.

Also it is likely required to update reset_summary_data() if the field type doesn't support a value of 0

The application must declare them as summary fields by defining:

class Client(Summarized, ...):

    def reset_summary_data(self):
        self.active_from = None
        self.active_untill = None

    def get_summary_collectors(self):
        yield (self.update_active_from, Contracts.objects.filter(client=self).orderby("start_date")[0:1])
        yield (self.update_active_until, Contracts.objects.filter(client=self).orderby("end_date")[0:1])

    def update_active_from(self, obj):
        self.active_from = obj.start_date

    def update_active_untill(self, obj):
        self.active_untill = obj.end_date

Note that when a new contract is added the client's active_from and active_untill fields are not updated unless you run: Client.compute_summary_values()

The Summarized model mixin

class lino.modlib.summaries.Summarized

Model mixin for database objects that have summary fields.

delete_them_all

Set this to True if all instances of this model should be considered temporary data to be deleted by checksummaries.

compute_results

Action for updating all the summary fields on this database object.

reset_summary_data()

Set all counters and sums to 0.

compute_summary_values()

Reset summary data fields (reset_summary_data()), for every collector (get_summary_collectors()) loop over its database objects and collect data, then save this record.

update_for_filter()

Runs compute_summary_values() on a a filtered queryset based on keyword arguments.

get_summary_collectors()

To be implemented by subclasses. This must yield a sequence of (collector, qs) tuples, where collector is a callable and qs a queryset. Lino will call collector for each obj in qs. The collector is responsible for updating that object.

class lino.modlib.summaries.SlaveSummarized

Mixin for Summarized models that are related to a master.

The master is another database object for which this summary data applies. Implementing subclasses must define a field named master which must be a foreignkey to the master model.

master

The target model of the master will automatically receive an action check_summaries.

The mixin also sets allow_cascaded_delete to 'master'.

class lino.modlib.summaries.MonthlySummarized

A Summarized that will have more than one entries per master, one for each month.

summary_period

Can be 'yearly' or 'monthly'.

year
month
class lino.modlib.summaries.MonthlySlaveSummary

A combination of SlaveSummary and MonthlySummarized.

The checksummaries admin command

checksummaries

Update the summary tables.

If no arguments are given, run it on all summaries.

Otherwise (not yet implemented) every positional argument is expected to be a model name in the form app_label.ModelName, and only these models are being updated.

Actions

lino.modlib.summaries.check_summaries

This plugin installs a check_summaries action

lino.modlib.summaries.get_summary_models()

Return a dict mapping each model which has at least one summary to a list of these summaries.

class lino.modlib.summaries.CheckSummaries

Web UI version of checksummaries.

class lino.modlib.summaries.UpdateSummariesByMaster

Update summary data for this object.

Plugin configuration

The plugin has two configurable attributes start_year and end_year which can be set to specify the years to be covered in summary tables. The default is the current year and two precedent ones.