sundhar010 opened a new issue, #35791:
URL: https://github.com/apache/beam/issues/35791
### What happened?
Summary:
Using WriteToParquet with a PyArrow schema where all fields are explicitly
set as nullable fails with a KeyError if any field is missing.
```...
File "/site-packages/apache_beam/io/parquetio.py", line 119, in process
self._buffer[i].append(row[n])
~~~^^^
KeyError: "email [while running 'Write to
Parquet/ParDo(_RowDictionariesToArrowTable)']"
```
Expected Behavior
If a field is marked as nullable=True in the schema and is missing in the
input dictionary, Beam should write a null value to the Parquet file instead of
throwing a KeyError.
Reproducible Code
```
import apache_beam as beam
from apache_beam.options.pipeline_options import PipelineOptions
from apache_beam.io.parquetio import WriteToParquet
import pyarrow as pa
import os
# Define PyArrow schema with all fields nullable
schema = pa.schema([
pa.field("id", pa.int64(), nullable=True),
pa.field("name", pa.string(), nullable=True),
pa.field("age", pa.int64(), nullable=True),
pa.field("email", pa.string(), nullable=True),
])
# Sample data
data = [
{'id': 1, 'name': 'Alice', 'age': 30, },
{'id': 2, 'name': 'Bob', 'age': 25, 'email': '[email protected]'},
{'id': 3, 'name': 'Charlie', 'age': None, 'email': None},
]
def run():
output_prefix = 'output/data'
output_dir = os.path.dirname(output_prefix)
os.makedirs(output_dir)
pipeline_options = PipelineOptions()
with beam.Pipeline(options=pipeline_options) as p:
(
p
| "Create Data" >> beam.Create(data)
| "Write to Parquet" >> WriteToParquet(
file_path_prefix=output_prefix,
schema=schema,
file_name_suffix='.parquet'
)
)
if __name__ == "__main__":
run()
```
Questions
Is this expected behavior, or should WriteToParquet default to null for
missing fields if the schema allows nulls?
Environment
Apache Beam version: 2.66.0
Python version: 3.13
Runner: DirectRunner
### Issue Priority
Priority: 2 (default / most bugs should be filed as P2)
### Issue Components
- [x] Component: Python SDK
- [ ] Component: Java SDK
- [ ] Component: Go SDK
- [ ] Component: Typescript SDK
- [x] Component: IO connector
- [ ] Component: Beam YAML
- [ ] Component: Beam examples
- [ ] Component: Beam playground
- [ ] Component: Beam katas
- [ ] Component: Website
- [ ] Component: Infrastructure
- [ ] Component: Spark Runner
- [ ] Component: Flink Runner
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- [ ] Component: Hazelcast Jet Runner
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