perf: Faster session startup by defering anon dataset fetch (#1982)

Author: TrevorBergeron

bigframes/session/anonymous_dataset.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import datetime
+import threading
 from typing import List, Optional, Sequence
 import uuid
 
@@ -40,19 +41,30 @@ def __init__(
  ):
  self.bqclient = bqclient
  self._location = location
- self.dataset = bf_io_bigquery.create_bq_dataset_reference(
- self.bqclient,
- location=self._location,
- )
 
  self.session_id = session_id
  self._table_ids: List[bigquery.TableReference] = []
  self._kms_key = kms_key
 
+ self._dataset_lock = threading.Lock()
+ self._datset_ref: Optional[bigquery.DatasetReference] = None
+
  @property
  def location(self):
  return self._location
 
+ @property
+ def dataset(self) -> bigquery.DatasetReference:
+ if self._datset_ref is not None:
+ return self._datset_ref
+ with self._dataset_lock:
+ if self._datset_ref is None:
+ self._datset_ref = bf_io_bigquery.create_bq_dataset_reference(
+ self.bqclient,
+ location=self._location,
+ )
+ return self._datset_ref
+
  def _default_expiration(self):
  """When should the table expire automatically?"""
  return (