def setup_session(cls):
global create_session
shard_lookup = {
"North America": "north_america",
"Asia": "asia",
"Europe": "europe",
"South America": "south_america",
}
def shard_chooser(mapper, instance, clause=None):
if isinstance(instance, WeatherLocation):
return shard_lookup[instance.continent]
else:
return shard_chooser(mapper, instance.location)
def id_chooser(query, ident):
return ["north_america", "asia", "europe", "south_america"]
def execute_chooser(orm_context):
ids = []
query = orm_context.statement
class FindContinent(sql.ClauseVisitor):
def visit_binary(self, binary):
if binary.left.shares_lineage(
weather_locations.c.continent
):
if binary.operator == operators.eq:
ids.append(shard_lookup[binary.right.value])
elif binary.operator == operators.in_op:
for value in binary.right.value:
ids.append(shard_lookup[value])
if query.whereclause is not None:
FindContinent().traverse(query.whereclause)
if len(ids) == 0:
return ["north_america", "asia", "europe", "south_america"]
else:
return ids
create_session = sessionmaker(
class_=ShardedSession, autoflush=True, autocommit=False
)
create_session.configure(
shards={
"north_america": db1,
"asia": db2,
"europe": db3,
"south_america": db4,
},
shard_chooser=shard_chooser,
id_chooser=id_chooser,
execute_chooser=execute_chooser,
)
def setup_session(cls):
global create_session
shard_lookup = {
"North America": "north_america",
"Asia": "asia",
"Europe": "europe",
"South America": "south_america",
}
def shard_chooser(mapper, instance, clause=None):
if isinstance(instance, WeatherLocation):
return shard_lookup[instance.continent]
else:
return shard_chooser(mapper, instance.location)
def id_chooser(query, 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.shares_lineage(
weather_locations.c.continent
):
if binary.operator == operators.eq:
ids.append(shard_lookup[binary.right.value])
elif binary.operator == operators.in_op:
for bind in binary.right.clauses:
ids.append(shard_lookup[bind.value])
if query._criterion is not None:
FindContinent().traverse(query._criterion)
if len(ids) == 0:
return ["north_america", "asia", "europe", "south_america"]
else:
return ids
create_session = sessionmaker(
class_=ShardedSession, autoflush=True, autocommit=False
)
create_session.configure(
shards={
"north_america": db1,
"asia": db2,
"europe": db3,
"south_america": db4,
},
shard_chooser=shard_chooser,
id_chooser=id_chooser,
query_chooser=query_chooser,
)