from link.middleware.core import Middleware

# Will open a QueryManager using a MongoDB backend
manager = Middleware.get_middleware_by_uri('query+mongo://localhost:27107/mydatabase/mycollection')
# Will open a QueryManager using a SQL backend
manager = Middleware.get_middleware_by_uri('query+sql://localhost:5432/mydatabase/mytable')

from link.dbrequest.expression import E, F
from link.dbrequest.assignment import A
from link.dbrequest.comparison import C


query = manager.all()  # get an iterable over all elements

manager.create(A('foo', 'bar'))  # put document {'foo': 'bar'} into database

doc = manager.get(C('foo') != 'bar')  # get single element, or None

docs = list(query)  # iterate over query to execute the request
docs = list(query)  # use cache when iterating again

# create a new query from the first one
q2 = query.filter(C('foo') == 'bar')
assert query is not q2

# exclude documents without a field named "bar"
q3 = q2.exclude(~C('bar'))

# filter documents "weight > 5" and "prop1 < prop2 * 5"
q4 = q3.filter((C('weight') > 5) & (C('prop1') < (E('prop2') * 5)))

# set "prop3 = prop1 + prop2" on q2 result
docs = q2.update(A('prop3', E('prop1') + E('prop2')))

# delete documents
q3.delete()

# save/delete a single document
doc.save()
doc.delete()