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'''Helper functions for reports'''
class BatchFetch(object):
'''Fetch Django objects in smaller batches to save memory'''
def __init__(self, obj, step=10000):
self.count = 0
self.block_count = 0
self.obj = obj
self.data = None
self.step = step
self.max = obj.count()
def __iter__(self):
return self
def next(self):
'''Return the next object from our array and fetch from the
database when needed'''
if self.block_count + self.count - self.step == self.max:
raise StopIteration
if self.block_count == 0 or self.count == self.step:
# Without list() this turns into LIMIT 1 OFFSET x queries
self.data = list(self.obj.all()[self.block_count: \
(self.block_count + self.step)])
self.block_count += self.step
self.count = 0
self.count += 1
return self.data[self.count - 1]
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