perf: DB-API uses more efficient query_and_wait when no job ID is provided

google/cloud/bigquery/_job_helpers.py

@@ -491,6 +491,7 @@ def do_query():
             job_id=query_results.job_id,
             query_id=query_results.query_id,
             project=query_results.project,
+            num_dml_affected_rows=query_results.num_dml_affected_rows,
         )
 
     if job_retry is not None:

google/cloud/bigquery/client.py

@@ -3963,6 +3963,7 @@ def _list_rows_from_query_results(
         timeout: TimeoutType = DEFAULT_TIMEOUT,
         query_id: Optional[str] = None,
         first_page_response: Optional[Dict[str, Any]] = None,
+        num_dml_affected_rows: Optional[int] = None,
     ) -> RowIterator:
         """List the rows of a completed query.
         See
@@ -4007,6 +4008,10 @@ def _list_rows_from_query_results(
                 and not guaranteed to be populated.
             first_page_response (Optional[dict]):
                 API response for the first page of results (if available).
+            num_dml_affected_rows (Optional[int]):
+                If this RowIterator is the result of a DML query, the number of
+                rows that were affected.
+
         Returns:
             google.cloud.bigquery.table.RowIterator:
                 Iterator of row data
@@ -4047,6 +4052,7 @@ def _list_rows_from_query_results(
             job_id=job_id,
             query_id=query_id,
             first_page_response=first_page_response,
+            num_dml_affected_rows=num_dml_affected_rows,
         )
         return row_iterator
 

google/cloud/bigquery/dbapi/cursor.py

@@ -14,11 +14,12 @@
 
 """Cursor for the Google BigQuery DB-API."""
 
+from __future__ import annotations
+
 import collections
 from collections import abc as collections_abc
-import copy
-import logging
 import re
+from typing import Optional
 
 try:
     from google.cloud.bigquery_storage import ArrowSerializationOptions
@@ -34,8 +35,6 @@
 import google.cloud.exceptions  # type: ignore
 
 
-_LOGGER = logging.getLogger(__name__)
-
 # Per PEP 249: A 7-item sequence containing information describing one result
 # column. The first two items (name and type_code) are mandatory, the other
 # five are optional and are set to None if no meaningful values can be
@@ -76,18 +75,31 @@ def __init__(self, connection):
         # most appropriate size.
         self.arraysize = None
         self._query_data = None
-        self._query_job = None
+        self._query_rows = None
         self._closed = False
 
     @property
-    def query_job(self):
-        """google.cloud.bigquery.job.query.QueryJob: The query job created by
-        the last ``execute*()`` call.
+    def query_job(self) -> Optional[job.QueryJob]:
+        """google.cloud.bigquery.job.query.QueryJob | None: The query job
+        created by the last ``execute*()`` call, if a query job was created.
 
         .. note::
             If the last ``execute*()`` call was ``executemany()``, this is the
             last job created by ``executemany()``."""
-        return self._query_job
+        rows = self._query_rows
+
+        if rows is None:
+            return None
+
+        job_id = rows.job_id
+        project = rows.project
+        location = rows.location
+        client = self.connection._client
+
+        if job_id is None:
+            return None
+
+        return client.get_job(job_id, location=location, project=project)
 
     def close(self):
         """Mark the cursor as closed, preventing its further use."""
@@ -117,8 +129,8 @@ def _set_description(self, schema):
             for field in schema
         )
 
-    def _set_rowcount(self, query_results):
-        """Set the rowcount from query results.
+    def _set_rowcount(self, rows):
+        """Set the rowcount from a RowIterator.
 
         Normally, this sets rowcount to the number of rows returned by the
         query, but if it was a DML statement, it sets rowcount to the number
@@ -129,10 +141,10 @@ def _set_rowcount(self, query_results):
                 Results of a query.
         """
         total_rows = 0
-        num_dml_affected_rows = query_results.num_dml_affected_rows
+        num_dml_affected_rows = rows.num_dml_affected_rows
 
-        if query_results.total_rows is not None and query_results.total_rows > 0:
-            total_rows = query_results.total_rows
+        if rows.total_rows is not None and rows.total_rows > 0:
+            total_rows = rows.total_rows
         if num_dml_affected_rows is not None and num_dml_affected_rows > 0:
             total_rows = num_dml_affected_rows
         self.rowcount = total_rows
@@ -165,9 +177,10 @@ def execute(self, operation, parameters=None, job_id=None, job_config=None):
             parameters (Union[Mapping[str, Any], Sequence[Any]]):
                 (Optional) dictionary or sequence of parameter values.
 
-            job_id (str):
-                (Optional) The job_id to use. If not set, a job ID
-                is generated at random.
+            job_id (str | None):
+                (Optional and discouraged) The job ID to use when creating
+                the query job. For best performance and reliability, manually
+                setting a job ID is discouraged.
 
             job_config (google.cloud.bigquery.job.QueryJobConfig):
                 (Optional) Extra configuration options for the query job.
@@ -181,7 +194,7 @@ def _execute(
         self, formatted_operation, parameters, job_id, job_config, parameter_types
     ):
         self._query_data = None
-        self._query_job = None
+        self._query_results = None
         client = self.connection._client
 
         # The DB-API uses the pyformat formatting, since the way BigQuery does
@@ -190,33 +203,35 @@ def _execute(
         # libraries.
         query_parameters = _helpers.to_query_parameters(parameters, parameter_types)
 
-        if client._default_query_job_config:
-            if job_config:
-                config = job_config._fill_from_default(client._default_query_job_config)
-            else:
-                config = copy.deepcopy(client._default_query_job_config)
-        else:
-            config = job_config or job.QueryJobConfig(use_legacy_sql=False)
-
+        config = job_config or job.QueryJobConfig()
         config.query_parameters = query_parameters
-        self._query_job = client.query(
-            formatted_operation, job_config=config, job_id=job_id
-        )
 
-        if self._query_job.dry_run:
-            self._set_description(schema=None)
-            self.rowcount = 0
-            return
-
-        # Wait for the query to finish.
+        # Start the query and wait for the query to finish.
         try:
-            self._query_job.result()
+            if job_id is not None:
+                rows = client.query(
+                    formatted_operation,
+                    job_config=job_config,
+                    job_id=job_id,
+                ).result(
+                    page_size=self.arraysize,
+                )
+            else:
+                rows = client.query_and_wait(
+                    formatted_operation,
+                    job_config=config,
+                    page_size=self.arraysize,
+                )
         except google.cloud.exceptions.GoogleCloudError as exc:
             raise exceptions.DatabaseError(exc)
 
-        query_results = self._query_job._query_results
-        self._set_rowcount(query_results)
-        self._set_description(query_results.schema)
+        self._query_rows = rows
+        self._set_description(rows.schema)
+
+        if config.dry_run:
+            self.rowcount = 0
+        else:
+            self._set_rowcount(rows)
 
     def executemany(self, operation, seq_of_parameters):
         """Prepare and execute a database operation multiple times.
@@ -250,25 +265,26 @@ def _try_fetch(self, size=None):
 
         Mutates self to indicate that iteration has started.
         """
-        if self._query_job is None:
+        if self._query_data is not None:
+            # Already started fetching the data.
+            return
+
+        rows = self._query_rows
+        if rows is None:
             raise exceptions.InterfaceError(
                 "No query results: execute() must be called before fetch."
             )
 
-        if self._query_job.dry_run:
-            self._query_data = iter([])
+        bqstorage_client = self.connection._bqstorage_client
+        if rows._should_use_bqstorage(
+            bqstorage_client,
+            create_bqstorage_client=False,
+        ):
+            rows_iterable = self._bqstorage_fetch(bqstorage_client)
+            self._query_data = _helpers.to_bq_table_rows(rows_iterable)
             return
 
-        if self._query_data is None:
-            bqstorage_client = self.connection._bqstorage_client
-
-            if bqstorage_client is not None:
-                rows_iterable = self._bqstorage_fetch(bqstorage_client)
-                self._query_data = _helpers.to_bq_table_rows(rows_iterable)
-                return
-
-            rows_iter = self._query_job.result(page_size=self.arraysize)
-            self._query_data = iter(rows_iter)
+        self._query_data = iter(rows)
 
     def _bqstorage_fetch(self, bqstorage_client):
         """Start fetching data with the BigQuery Storage API.
@@ -290,7 +306,7 @@ def _bqstorage_fetch(self, bqstorage_client):
         # bigquery_storage can indeed be imported here without errors.
         from google.cloud import bigquery_storage
 
-        table_reference = self._query_job.destination
+        table_reference = self._query_rows._table
 
         requested_session = bigquery_storage.types.ReadSession(
             table=table_reference.to_bqstorage(),

google/cloud/bigquery/job/query.py

@@ -1614,6 +1614,7 @@ def do_get_result():
                 project=self.project,
                 job_id=self.job_id,
                 query_id=self.query_id,
+                num_dml_affected_rows=self._query_results.num_dml_affected_rows,
             )
 
         # We know that there's at least 1 row, so only treat the response from
@@ -1639,6 +1640,7 @@ def do_get_result():
             timeout=timeout,
             query_id=self.query_id,
             first_page_response=first_page_response,
+            num_dml_affected_rows=self._query_results.num_dml_affected_rows,
         )
         rows._preserve_order = _contains_order_by(self.query)
         return rows

google/cloud/bigquery/table.py

@@ -1566,6 +1566,7 @@ def __init__(
         job_id: Optional[str] = None,
         query_id: Optional[str] = None,
         project: Optional[str] = None,
+        num_dml_affected_rows: Optional[int] = None,
     ):
         super(RowIterator, self).__init__(
             client,
@@ -1592,6 +1593,7 @@ def __init__(
         self._job_id = job_id
         self._query_id = query_id
         self._project = project
+        self._num_dml_affected_rows = num_dml_affected_rows
 
     @property
     def _billing_project(self) -> Optional[str]:
@@ -1616,6 +1618,16 @@ def location(self) -> Optional[str]:
         """
         return self._location
 
+    @property
+    def num_dml_affected_rows(self) -> Optional[int]:
+        """If this RowIterator is the result of a DML query, the number of
+        rows that were affected.
+
+        See:
+        https://cloud.google.com/bigquery/docs/reference/rest/v2/jobs/query#body.QueryResponse.FIELDS.num_dml_affected_rows
+        """
+        return self._num_dml_affected_rows
+
     @property
     def project(self) -> Optional[str]:
         """GCP Project ID where these rows are read from."""
@@ -1635,7 +1647,10 @@ def _is_almost_completely_cached(self):
         This is useful to know, because we can avoid alternative download
         mechanisms.
         """
-        if self._first_page_response is None:
+        if (
+            not hasattr(self, "_first_page_response")
+            or self._first_page_response is None
+        ):
             return False
 
         total_cached_rows = len(self._first_page_response.get(self._items_key, []))
@@ -1655,7 +1670,7 @@ def _is_almost_completely_cached(self):
 
         return False
 
-    def _validate_bqstorage(self, bqstorage_client, create_bqstorage_client):
+    def _should_use_bqstorage(self, bqstorage_client, create_bqstorage_client):
         """Returns True if the BigQuery Storage API can be used.
 
         Returns:
@@ -1669,8 +1684,9 @@ def _validate_bqstorage(self, bqstorage_client, create_bqstorage_client):
         if self._table is None:
             return False
 
-        # The developer is manually paging through results if this is set.
-        if self.next_page_token is not None:
+        # The developer has already started paging through results if
+        # next_page_token is set.
+        if hasattr(self, "next_page_token") and self.next_page_token is not None:
             return False
 
         if self._is_almost_completely_cached():
@@ -1726,7 +1742,7 @@ def schema(self):
 
     @property
     def total_rows(self):
-        """int: The total number of rows in the table."""
+        """int: The total number of rows in the table or query results."""
         return self._total_rows
 
     def _maybe_warn_max_results(
@@ -1752,7 +1768,7 @@ def _maybe_warn_max_results(
     def _to_page_iterable(
         self, bqstorage_download, tabledata_list_download, bqstorage_client=None
     ):
-        if not self._validate_bqstorage(bqstorage_client, False):
+        if not self._should_use_bqstorage(bqstorage_client, False):
             bqstorage_client = None
 
         result_pages = (
@@ -1882,7 +1898,7 @@ def to_arrow(
 
         self._maybe_warn_max_results(bqstorage_client)
 
-        if not self._validate_bqstorage(bqstorage_client, create_bqstorage_client):
+        if not self._should_use_bqstorage(bqstorage_client, create_bqstorage_client):
             create_bqstorage_client = False
             bqstorage_client = None
 
@@ -2223,7 +2239,7 @@ def to_dataframe(
 
         self._maybe_warn_max_results(bqstorage_client)
 
-        if not self._validate_bqstorage(bqstorage_client, create_bqstorage_client):
+        if not self._should_use_bqstorage(bqstorage_client, create_bqstorage_client):
             create_bqstorage_client = False
             bqstorage_client = None