def get_sequences(self, model, num_children, shard_range):
output = []
our_epoch = int(time.mktime(datetime(2012, 11, 1).timetuple()) * 1000)
proc = """CREATE OR REPLACE FUNCTION next_sharded_id(varchar, int, OUT result bigint) AS $$
DECLARE
sequence_name ALIAS FOR $1;
shard_id ALIAS FOR $2;
seq_id bigint;
now_millis bigint;
BEGIN
SELECT nextval(sequence_name::regclass) % 1024 INTO seq_id;
SELECT FLOOR(EXTRACT(EPOCH FROM clock_timestamp()) * 1000) INTO now_millis;
result := (now_millis - {our_epoch}) << 23;
result := result | (shard_id << 10);
result := result | (seq_id);
END;
$$ LANGUAGE PLPGSQL;""".format(
our_epoch=our_epoch
)
output.append(self.style.SQL_KEYWORD(proc))
for i in shard_range:
child = generate_child_partition(model, i)
output.append(
self.style.SQL_KEYWORD("CREATE SEQUENCE ")
+ self.style.SQL_TABLE(get_sharded_id_sequence_name(child))
+ ";"
)
return output
def db_type(self, *args, **kwargs):
if not hasattr(self.model, '_shards'):
raise ValueError("ShardedAutoField must be used with a PartitionModel.")
if self.model._shards.is_master:
return "bigint"
return "bigint DEFAULT next_sharded_id('%s'::varchar, %d)" % (
get_sharded_id_sequence_name(self.model),
self.model._shards.num)
def create_sequence(self, created_models, **kwargs):
# Sequence creation for production is handled by DDL scripts
# (sqlpartition). This is needed to create sequences for
# test models.
if self.model not in created_models:
return
db_alias = self.model._shards.cluster
for child in self.model._shards.nodes:
cursor = connections[db_alias].cursor()
sid = transaction.savepoint(db_alias)
sequence_name = get_sharded_id_sequence_name(child)
try:
cursor.execute("CREATE SEQUENCE %s;" % sequence_name)
except DatabaseError:
transaction.savepoint_rollback(sid, using=db_alias)
# Sequence must already exist, ensure it gets reset
cursor.execute("SELECT setval('%s', 1, false)" % (sequence_name,))
else:
print 'Created sequence %r on %r' % (sequence_name, db_alias)
transaction.savepoint_commit(sid, using=db_alias)
cursor.close()
def create_sequence(self, created_models, **kwargs):
# Sequence creation for production is handled by DDL scripts
# (sqlpartition). This is needed to create sequences for
# test models.
if self.model not in created_models:
return
db_alias = self.model._shards.cluster
for child in self.model._shards.nodes:
cursor = connections[db_alias].cursor()
sid = transaction.savepoint(db_alias)
sequence_name = get_sharded_id_sequence_name(child)
try:
cursor.execute("CREATE SEQUENCE %s;" % sequence_name)
except DatabaseError:
transaction.savepoint_rollback(sid, using=db_alias)
# Sequence must already exist, ensure it gets reset
cursor.execute("SELECT setval('%s', 1, false)" %
(sequence_name, ))
else:
print 'Created sequence %r on %r' % (sequence_name, db_alias)
transaction.savepoint_commit(sid, using=db_alias)
cursor.close()
