Ardagan commented on a change in pull request #11582:
URL: https://github.com/apache/beam/pull/11582#discussion_r422903477
##########
File path: sdks/python/apache_beam/io/gcp/bigquery.py
##########
@@ -1641,3 +1644,314 @@ def process(self, unused_element, signal):
*self._args,
**self._kwargs))
| _PassThroughThenCleanup(RemoveJsonFiles(gcs_location)))
+
+
+class _ExtractBQData(DoFn):
+ '''
+ PTransform:ReadAllFromBigQueryRequest->FileMetadata that fetches BQ data into
+ a temporary storage and returns metadata for created files.
+ '''
+ def __init__(
+ self,
+ gcs_location_pattern=None,
+ project=None,
+ coder=None,
+ schema=None,
+ kms_key=None):
+
+ self.gcs_location_pattern = gcs_location_pattern
+ self.project = project
+ self.coder = coder or _JsonToDictCoder
+ self.kms_key = kms_key
+ self.split_result = None
+ self.schema = schema
+ self.target_schema = None
+
+ def process(self, element):
+ '''
+ :param element(ReadAllFromBigQueryRequest):
+ :return:
+ '''
+ element.validate()
+ if element.table is not None:
+ table_reference = bigquery_tools.parse_table_reference(element.table)
+ query = None
+ use_legacy_sql = True
+ else:
+ query = element.query
+ use_legacy_sql = element.use_legacy_sql
+
+ flatten_results = element.flatten_results
+
+ bq = bigquery_tools.BigQueryWrapper()
+
+ try:
+ if element.query is not None:
+ self._setup_temporary_dataset(bq, query, use_legacy_sql)
+ table_reference = self._execute_query(
+ bq, query, use_legacy_sql, flatten_results)
+
+ gcs_location = self.gcs_location_pattern.format(uuid.uuid4().hex)
+
+ table_schema = bq.get_table(
+ table_reference.projectId,
+ table_reference.datasetId,
+ table_reference.tableId).schema
+
+ if self.target_schema is None:
+ self.target_schema = bigquery_tools.parse_table_schema_from_json(
+ json.dumps(self.schema))
+
+ if not self.target_schema == table_schema:
Review comment:
We need schema to parse files generated from BQ export. I also use it to
verify all queries return same data format.
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