Refactor load_table methods to reduce code duplication

This commit refactors the `load_table_from_uri`, `load_table_from_file`,
`load_table_from_dataframe`, and `load_table_from_json` methods in the
BigQuery client.

A new private helper method, `_prepare_load_job`, has been introduced to
centralize the creation and configuration of `LoadJob` objects. This
eliminates redundant code for setting up job IDs, projects, and locations.

A second helper, `_prepare_load_config`, was also added to standardize
the handling of `LoadJobConfig` objects, merging user-provided
configurations with client defaults.

These changes make the loading methods more concise, easier to read, and
simpler to maintain.

Author: google-labs-jules[bot]

google/cloud/bigquery/client.py

@@ -2490,6 +2490,51 @@ def api_request(*args, **kwargs):
             page_size=page_size,
         )
 
+    def _prepare_load_config(
+        self, job_config: Optional[LoadJobConfig] = None
+    ) -> LoadJobConfig:
+        """Helper to construct a load job configuration.
+
+        Args:
+            job_config (Optional[google.cloud.bigquery.job.LoadJobConfig]):
+                A user-supplied job configuration.
+
+        Returns:
+            google.cloud.bigquery.job.LoadJobConfig:
+                The job configuration to use for a load job.
+        """
+        if job_config is not None:
+            _verify_job_config_type(job_config, LoadJobConfig)
+        else:
+            job_config = job.LoadJobConfig()
+
+        return job_config._fill_from_default(self._default_load_job_config)
+
+    def _prepare_load_job(
+        self,
+        destination: Union[Table, TableReference, str],
+        job_config: LoadJobConfig,
+        job_id: Optional[str] = None,
+        job_id_prefix: Optional[str] = None,
+        location: Optional[str] = None,
+        project: Optional[str] = None,
+        source_uris: Optional[Sequence[str]] = None,
+    ) -> job.LoadJob:
+        """Helper for `load_table_from_` methods to prepare a LoadJob."""
+        job_id = _make_job_id(job_id, job_id_prefix)
+
+        if project is None:
+            project = self.project
+
+        if location is None:
+            location = self.location
+
+        job_ref = job._JobReference(job_id, project=project, location=location)
+
+        destination = _table_arg_to_table_ref(destination, default_project=self.project)
+
+        return job.LoadJob(job_ref, source_uris, destination, self, job_config)
+
     def load_table_from_uri(
         self,
         source_uris: Union[str, Sequence[str]],
@@ -2547,31 +2592,21 @@ def load_table_from_uri(
                 If ``job_config`` is not an instance of
                 :class:`~google.cloud.bigquery.job.LoadJobConfig` class.
         """
-        job_id = _make_job_id(job_id, job_id_prefix)
-
-        if project is None:
-            project = self.project
-
-        if location is None:
-            location = self.location
-
-        job_ref = job._JobReference(job_id, project=project, location=location)
-
         if isinstance(source_uris, str):
             source_uris = [source_uris]
 
-        destination = _table_arg_to_table_ref(destination, default_project=self.project)
-
-        if job_config is not None:
-            _verify_job_config_type(job_config, LoadJobConfig)
-        else:
-            job_config = job.LoadJobConfig()
-
-        new_job_config = job_config._fill_from_default(self._default_load_job_config)
+        new_job_config = self._prepare_load_config(job_config)
+        load_job = self._prepare_load_job(
+            destination,
+            new_job_config,
+            job_id=job_id,
+            job_id_prefix=job_id_prefix,
+            location=location,
+            project=project,
+            source_uris=source_uris,
+        )
 
-        load_job = job.LoadJob(job_ref, source_uris, destination, self, new_job_config)
         load_job._begin(retry=retry, timeout=timeout)
-
         return load_job
 
     def load_table_from_file(
@@ -2647,25 +2682,15 @@ def load_table_from_file(
                 If ``job_config`` is not an instance of
                 :class:`~google.cloud.bigquery.job.LoadJobConfig` class.
         """
-        job_id = _make_job_id(job_id, job_id_prefix)
-
-        if project is None:
-            project = self.project
-
-        if location is None:
-            location = self.location
-
-        destination = _table_arg_to_table_ref(destination, default_project=self.project)
-        job_ref = job._JobReference(job_id, project=project, location=location)
-
-        if job_config is not None:
-            _verify_job_config_type(job_config, LoadJobConfig)
-        else:
-            job_config = job.LoadJobConfig()
-
-        new_job_config = job_config._fill_from_default(self._default_load_job_config)
-
-        load_job = job.LoadJob(job_ref, None, destination, self, new_job_config)
+        new_job_config = self._prepare_load_config(job_config)
+        load_job = self._prepare_load_job(
+            destination,
+            new_job_config,
+            job_id=job_id,
+            job_id_prefix=job_id_prefix,
+            location=location,
+            project=project,
+        )
         job_resource = load_job.to_api_repr()
 
         if rewind:
@@ -2796,14 +2821,7 @@ def load_table_from_dataframe(
                 If ``job_config`` is not an instance of
                 :class:`~google.cloud.bigquery.job.LoadJobConfig` class.
         """
-        job_id = _make_job_id(job_id, job_id_prefix)
-
-        if job_config is not None:
-            _verify_job_config_type(job_config, LoadJobConfig)
-        else:
-            job_config = job.LoadJobConfig()
-
-        new_job_config = job_config._fill_from_default(self._default_load_job_config)
+        new_job_config = self._prepare_load_config(job_config)
 
         supported_formats = {job.SourceFormat.CSV, job.SourceFormat.PARQUET}
         if new_job_config.source_format is None:
@@ -2830,9 +2848,6 @@ def load_table_from_dataframe(
             # pyarrow is now the only supported parquet engine.
             raise ValueError("This method requires pyarrow to be installed")
 
-        if location is None:
-            location = self.location
-
         # If table schema is not provided, we try to fetch the existing table
         # schema, and check if dataframe schema is compatible with it - except
         # for WRITE_TRUNCATE jobs, the existing schema does not matter then.
@@ -2877,8 +2892,14 @@ def load_table_from_dataframe(
                 stacklevel=2,
             )
 
+        # We need a unique suffix for every load_table_from_dataframe call to
+        # avoid collisions.
+        # See: https://github.com/googleapis/python-bigquery/issues/1363
+        session_suffix = uuid.uuid4().hex
         tmpfd, tmppath = tempfile.mkstemp(
-            suffix="_job_{}.{}".format(job_id[:8], new_job_config.source_format.lower())
+            suffix="_job_{}.{}".format(
+                session_suffix, new_job_config.source_format.lower()
+            )
         )
         os.close(tmpfd)
 
@@ -3012,15 +3033,7 @@ def load_table_from_json(
                 If ``job_config`` is not an instance of
                 :class:`~google.cloud.bigquery.job.LoadJobConfig` class.
         """
-        job_id = _make_job_id(job_id, job_id_prefix)
-
-        if job_config is not None:
-            _verify_job_config_type(job_config, LoadJobConfig)
-        else:
-            job_config = job.LoadJobConfig()
-
-        new_job_config = job_config._fill_from_default(self._default_load_job_config)
-
+        new_job_config = self._prepare_load_config(job_config)
         new_job_config.source_format = job.SourceFormat.NEWLINE_DELIMITED_JSON
 
         # In specific conditions, we check if the table alread exists, and/or
@@ -3040,14 +3053,6 @@ def load_table_from_json(
                 else:
                     new_job_config.autodetect = False
 
-        if project is None:
-            project = self.project
-
-        if location is None:
-            location = self.location
-
-        destination = _table_arg_to_table_ref(destination, default_project=self.project)
-
         data_str = "\n".join(json.dumps(item, ensure_ascii=False) for item in json_rows)
         encoded_str = data_str.encode()
         data_file = io.BytesIO(encoded_str)