def start_transaction(self):
request = prestodb.client.PrestoRequest(
self.host,
self.port,
self.user,
self.source,
self.catalog,
self.schema,
self.session_properties,
self.http_headers,
NO_TRANSACTION,
self.http_scheme,
self.auth,
self.redirect_handler,
self.max_attempts,
self.request_timeout,
)
self._transaction = Transaction(request)
self._transaction.begin()
return self._transaction
class Connection(object):
"""Presto supports transactions and the ability to either commit or rollback
a sequence of SQL statements. A single query i.e. the execution of a SQL
statement, can also be cancelled. Transactions are not supported by this
client implementation yet.
"""
def __init__(
self,
host,
port=constants.DEFAULT_PORT,
user=None,
password=None,
resource_group="default",
source=constants.DEFAULT_SOURCE,
catalog=constants.DEFAULT_CATALOG,
schema=constants.DEFAULT_SCHEMA,
session_properties=None,
http_headers=None,
http_scheme=constants.HTTP,
auth=constants.DEFAULT_AUTH,
redirect_handler=prestodb.redirect.GatewayRedirectHandler(),
max_attempts=constants.DEFAULT_MAX_ATTEMPTS,
request_timeout=constants.DEFAULT_REQUEST_TIMEOUT,
isolation_level=IsolationLevel.AUTOCOMMIT,
):
self.host = host
self.port = port
self.user = user
self.password = password
self.resource_group = resource_group
self.source = source
self.catalog = catalog
self.schema = schema
self.session_properties = session_properties
# mypy cannot follow module import
self._http_session = prestodb.client.PrestoRequest.http.Session()
self.http_headers = http_headers
self.http_scheme = http_scheme
self.auth = auth
self.redirect_handler = redirect_handler
self.max_attempts = max_attempts
self.request_timeout = request_timeout
self._isolation_level = isolation_level
self._request = None
self._transaction = None
@property
def isolation_level(self):
return self._isolation_level
@property
def transaction(self):
return self._transaction
def __enter__(self):
return self
def __exit__(self, exc_type, exc_value, traceback):
try:
self.commit()
except Exception:
self.rollback()
else:
self.close()
def close(self):
"""Presto does not have anything to close"""
# TODO cancel outstanding queries?
pass
def start_transaction(self):
self._transaction = Transaction(self._create_request())
self._transaction.begin()
return self._transaction
def commit(self):
if self.transaction is None:
return
self._transaction.commit()
self._transaction = None
def rollback(self):
if self.transaction is None:
raise RuntimeError('no transaction was started')
self._transaction.rollback()
self._transaction = None
def _create_request(self):
return prestodb.client.PrestoRequest(
self.host,
self.port,
self.user,
self.password,
self.resource_group,
self.source,
self.catalog,
self.schema,
self.session_properties,
self._http_session,
self.http_headers,
NO_TRANSACTION,
self.http_scheme,
self.auth,
self.redirect_handler,
self.max_attempts,
self.request_timeout,
)
def cursor(self):
"""Return a new :py:class:`Cursor` object using the connection."""
if self.isolation_level != IsolationLevel.AUTOCOMMIT:
if self.transaction is None:
self.start_transaction()
request = self.transaction._request
else:
request = self._create_request()
return Cursor(self, request)
def start_transaction(self):
self._transaction = Transaction(self._create_request())
self._transaction.begin()
return self._transaction