from sqlalchemy import func
from babbage.model.concept import Concept
class Aggregate(Concept):
""" An aggregates describes the application of an aggregate function (such
as summing, averages, counts etc.) to a measure or the primary key of the
cube. """
def __init__(self, model, label, function, measure=None):
super(Aggregate, self).__init__(model, None, {'label': label})
self.function = function
self.measure = measure
@property
def ref(self):
if self.measure is not None:
return '%s.%s' % (self.measure.ref, self.function)
return '_%s' % self.function
def bind(self, cube):
""" When one column needs to match, use the key. """
if self.measure:
table, column = self.measure.bind(cube)
else:
table, column = cube.fact_table, cube.fact_pk
# apply the SQL aggregation function:
column = getattr(func, self.function)(column)
column = column.label(self.ref)
column.quote = True
return table, column
def __repr__(self):
return "<Aggregate(%s)>" % self.ref
def to_dict(self):
data = self.spec.copy()
data['ref'] = self.ref
data['function'] = self.function
if self.measure is not None:
data['measure'] = self.measure.ref
return data
