vachan-shetty commented on a change in pull request #15185:
URL: https://github.com/apache/beam/pull/15185#discussion_r685572461
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File path: sdks/python/apache_beam/io/gcp/bigquery.py
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@@ -883,6 +893,274 @@ def _export_files(self, bq):
return table.schema, metadata_list
+class _CustomBigQueryStorageSourceBase(BoundedSource):
+ """A base class for BoundedSource implementations which read from BigQuery
+ using the BigQuery Storage API.
+
+ Args:
+ table (str, TableReference): The ID of the table. The ID must contain only
+ letters ``a-z``, ``A-Z``, numbers ``0-9``, or underscores ``_`` If
+ **dataset** argument is :data:`None` then the table argument must
+ contain the entire table reference specified as:
+ ``'PROJECT:DATASET.TABLE'`` or must specify a TableReference.
+ dataset (str): Optional ID of the dataset containing this table or
+ :data:`None` if the table argument specifies a TableReference.
+ project (str): Optional ID of the project containing this table or
+ :data:`None` if the table argument specifies a TableReference.
+ selected_fields (List[str]): Optional List of names of the fields in the
+ table that should be read. If empty, all fields will be read. If the
+ specified field is a nested field, all the sub-fields in the field will
be
+ selected. The output field order is unrelated to the order of fields in
+ selected_fields.
+ row_restriction (str): Optional SQL text filtering statement, similar to a
+ WHERE clause in a query. Aggregates are not supported. Restricted to a
+ maximum length for 1 MB.
+ """
+
+ # The maximum number of streams which will be requested when creating a read
+ # session, regardless of the desired bundle size.
+ MAX_SPLIT_COUNT = 10000
+ # The minimum number of streams which will be requested when creating a read
+ # session, regardless of the desired bundle size. Note that the server may
+ # still choose to return fewer than ten streams based on the layout of the
+ # table.
+ MIN_SPLIT_COUNT = 10
+
+ def __init__(
+ self,
+ table: Union[str, TableReference],
+ dataset: Optional[str] = None,
+ project: Optional[str] = None,
+ selected_fields: Optional[List[str]] = None,
+ row_restriction: Optional[str] = None,
+ use_fastavro: Optional[bool] = None,
Review comment:
Updated `estimate_size()` which should improve autoscaling in [theory].
There should be further improvements in autoscaling once we add support dynamic
work rebalancing. Additionally, I intend to remove the non-fastavro parsing in
a follow-up PR where the Storage API source and the core `avroio` source are
combined together.
[theory]:
https://cloud.google.com/dataflow/docs/guides/deploying-a-pipeline#batch-autoscaling
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