60 lines
1.6 KiB
Python
60 lines
1.6 KiB
Python
from copy import copy
|
|
|
|
|
|
class QueryChain(object):
|
|
"""
|
|
:param queries: A sequence of SQLAlchemy Query objects
|
|
:param limit: Similar to normal query limit this parameter can be used for
|
|
limiting the number of results for the whole query chain.
|
|
:param offset: Similar to normal query offset this parameter can be used
|
|
for offsetting the query chain as a whole.
|
|
|
|
::
|
|
|
|
chain = QueryChain([session.query(User), session.query(Article)])
|
|
|
|
for obj in chain[0:5]:
|
|
print obj
|
|
|
|
.. versionadded: 0.26.0
|
|
"""
|
|
def __init__(self, queries, limit=None, offset=None):
|
|
self.queries = queries
|
|
self.limit = limit
|
|
self.offset = offset
|
|
|
|
def __iter__(self):
|
|
consumed = 0
|
|
skipped = 0
|
|
for query in self.queries:
|
|
query_copy = copy(query)
|
|
if self.limit:
|
|
query = query.limit(self.limit - consumed)
|
|
if self.offset:
|
|
query = query.offset(self.offset - skipped)
|
|
|
|
obj_count = 0
|
|
for obj in query:
|
|
consumed += 1
|
|
obj_count += 1
|
|
yield obj
|
|
|
|
if not obj_count:
|
|
skipped += query_copy.count()
|
|
else:
|
|
skipped += obj_count
|
|
|
|
def __getitem__(self, key):
|
|
if isinstance(key, slice):
|
|
return self.__class__(
|
|
queries=self.queries,
|
|
limit=key.stop,
|
|
offset=key.start
|
|
)
|
|
else:
|
|
for obj in self[key:1]:
|
|
return obj
|
|
|
|
def __repr__(self):
|
|
return '<QueryChain at 0x%x>' % id(self)
|