21 lines
626 B
Python
21 lines
626 B
Python
|
def windowed_query(query, column, window_size):
|
||
|
|
""""
|
||
|
|
Break a Query into chunks on a given column.
|
||
|
|
|
||
|
|
see: https://github.com/sqlalchemy/sqlalchemy/wiki/RangeQuery-and-WindowedRangeQuery
|
||
|
|
"""
|
||
|
|
single_entity = query.is_single_entity
|
||
|
|
query = query.add_columns(column).order_by(column)
|
||
|
|
last_id = None
|
||
|
|
|
||
|
|
while True:
|
||
|
|
sub_query = query
|
||
|
|
if last_id is not None:
|
||
|
|
sub_query = sub_query.filter(column > last_id)
|
||
|
|
chunk = sub_query.limit(window_size).all()
|
||
|
|
if not chunk:
|
||
|
|
break
|
||
|
|
last_id = chunk[-1][-1]
|
||
|
|
for row in chunk:
|
||
|
|
yield row
|