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import testbase
from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.orm.shard import ShardedSession
from sqlalchemy.sql import ColumnOperators
import datetime, operator, os
from testlib import PersistTest
# TODO: ShardTest can be turned into a base for further subclasses
class ShardTest(PersistTest):
def setUpAll(self):
global db1, db2, db3, db4, weather_locations, weather_reports
db1 = create_engine('sqlite:///shard1.db')
db2 = create_engine('sqlite:///shard2.db')
db3 = create_engine('sqlite:///shard3.db')
db4 = create_engine('sqlite:///shard4.db')
meta = MetaData()
ids = Table('ids', meta,
Column('nextid', Integer, nullable=False))
def id_generator(ctx):
# in reality, might want to use a separate transaction for this.
c = db1.connect()
nextid = c.execute(ids.select(for_update=True)).scalar()
c.execute(ids.update(values={ids.c.nextid : ids.c.nextid + 1}))
return nextid
weather_locations = Table("weather_locations", meta,
Column('id', Integer, primary_key=True, default=id_generator),
Column('continent', String(30), nullable=False),
Column('city', String(50), nullable=False)
)
weather_reports = Table("weather_reports", meta,
Column('id', Integer, primary_key=True),
Column('location_id', Integer, ForeignKey('weather_locations.id')),
Column('temperature', Float),
Column('report_time', DateTime, default=datetime.datetime.now),
)
for db in (db1, db2, db3, db4):
meta.create_all(db)
db1.execute(ids.insert(), nextid=1)
self.setup_session()
self.setup_mappers()
def tearDownAll(self):
for i in range(1,5):
os.remove("shard%d.db" % i)
def setup_session(self):
global create_session
shard_lookup = {
'North America':'north_america',
'Asia':'asia',
'Europe':'europe',
'South America':'south_america'
}
def shard_chooser(mapper, instance):
if isinstance(instance, WeatherLocation):
return shard_lookup[instance.continent]
else:
return shard_chooser(mapper, instance.location)
def id_chooser(ident):
return ['north_america', 'asia', 'europe', 'south_america']
def query_chooser(query):
ids = []
class FindContinent(sql.ClauseVisitor):
def visit_binary(self, binary):
if binary.left is weather_locations.c.continent:
if binary.operator == operator.eq:
ids.append(shard_lookup[binary.right.value])
elif binary.operator == ColumnOperators.in_op:
for bind in binary.right.clauses:
ids.append(shard_lookup[bind.value])
FindContinent().traverse(query._criterion)
if len(ids) == 0:
return ['north_america', 'asia', 'europe', 'south_america']
else:
return ids
def create_session():
s = ShardedSession(shard_chooser, id_chooser, query_chooser)
s.bind_shard('north_america', db1)
s.bind_shard('asia', db2)
s.bind_shard('europe', db3)
s.bind_shard('south_america', db4)
return s
def setup_mappers(self):
global WeatherLocation, Report
class WeatherLocation(object):
def __init__(self, continent, city):
self.continent = continent
self.city = city
class Report(object):
def __init__(self, temperature):
self.temperature = temperature
mapper(WeatherLocation, weather_locations, properties={
'reports':relation(Report, backref='location')
})
mapper(Report, weather_reports)
def test_roundtrip(self):
tokyo = WeatherLocation('Asia', 'Tokyo')
newyork = WeatherLocation('North America', 'New York')
toronto = WeatherLocation('North America', 'Toronto')
london = WeatherLocation('Europe', 'London')
dublin = WeatherLocation('Europe', 'Dublin')
brasilia = WeatherLocation('South America', 'Brasila')
quito = WeatherLocation('South America', 'Quito')
tokyo.reports.append(Report(80.0))
newyork.reports.append(Report(75))
quito.reports.append(Report(85))
sess = create_session()
for c in [tokyo, newyork, toronto, london, dublin, brasilia, quito]:
sess.save(c)
sess.flush()
sess.clear()
t = sess.query(WeatherLocation).get(tokyo.id)
assert t.city == tokyo.city
assert t.reports[0].temperature == 80.0
north_american_cities = sess.query(WeatherLocation).filter(WeatherLocation.continent == 'North America')
assert set([c.city for c in north_american_cities]) == set(['New York', 'Toronto'])
asia_and_europe = sess.query(WeatherLocation).filter(WeatherLocation.continent.in_('Europe', 'Asia'))
assert set([c.city for c in asia_and_europe]) == set(['Tokyo', 'London', 'Dublin'])
if __name__ == '__main__':
testbase.main()
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