This repository was archived by the owner on Nov 12, 2025. It is now read-only.
This repository was archived by the owner on Nov 12, 2025. It is now read-only.
ValueError: No objects to concatenate in to_dataframe method #27
Description
If you have a small query result set and many streams, then often one of the reading streams doesn't get any pages to read (probably other streams get to read all the data before ??)
Pandas doesn't allow concat on empty list. return pandas.concat(frames)
In this case the following exception occurs
File "***/lib/python3.7/site-packages/google/cloud/bigquery_storage_v1/reader.py", line 236, in to_dataframe
return self.rows(read_session).to_dataframe(dtypes=dtypes)
File "***/lib/python3.7/site-packages/google/cloud/bigquery_storage_v1/reader.py", line 336, in to_dataframe
return pandas.concat(frames)
File "***/lib/python3.7/site-packages/pandas/core/reshape/concat.py", line 255, in concat
sort=sort,
File "***/lib/python3.7/site-packages/pandas/core/reshape/concat.py", line 304, in __init__
raise ValueError("No objects to concatenate")
ValueError: No objects to concatenate