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fix: handle DuckDB arrow() returning multiple types in duckdb_demo #48

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cning112 merged 1 commit into from
May 2, 2026
Merged

fix: handle DuckDB arrow() returning multiple types in duckdb_demo #48

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15 changes: 14 additions & 1 deletion examples/multi_protocol_demo/demo_services/duckdb_demo.py
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Original file line number Diff line number Diff line change
Expand Up @@ -37,8 +37,21 @@ def _iterate_duckdb_batches(params: DuckDBParams, batch_size: int | None = None)

with duckdb.connect(db_path) as conn:
logger.debug(f"Executing query: {params.query}")
reader: pa.RecordBatchReader = conn.execute(params.query, query_parameters).arrow() # type: ignore[assignment]
arrow_obj: Any = conn.execute(params.query, query_parameters).arrow()

reader: pa.RecordBatchReader
if isinstance(arrow_obj, pa.RecordBatchReader): # type: ignore[unreachable, unused-ignore]
reader = arrow_obj
elif isinstance(arrow_obj, pa.RecordBatch): # type: ignore[unreachable, unused-ignore]
reader = pa.RecordBatchReader.from_batches(arrow_obj.schema, [arrow_obj])
elif isinstance(arrow_obj, pa.Table): # type: ignore[unreachable, unused-ignore]
reader = arrow_obj.to_reader()
else:
raise TypeError(f"Unexpected DuckDB Arrow result type: {type(arrow_obj)!r}")

for batch in reader:
if batch.num_rows == 0:
continue
if batch_size and batch.num_rows > batch_size:
for offset in range(0, batch.num_rows, batch_size):
yield batch.slice(offset, min(batch_size, batch.num_rows - offset))
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