Kuinox opened a new issue, #48254:
URL: https://github.com/apache/arrow/issues/48254
### Describe the bug, including details regarding any error messages,
version, and platform.
### Summary
UUID extension types are preserved in tables but dropped by
`pyarrow.parquet.read_schema`, creating an asymmetry between the table’s schema
and the schema read from Parquet metadata.
### Steps to Reproduce
```python
import pyarrow as pa
import pyarrow.parquet as pq
from pathlib import Path
import tempfile
data = [
b'\xe4`\xf9p\x83QGN\xac\x7f\xa4g>\x4b\xa8\xcb',
b'\x1et\x14\x95\xee\xd5C\xea\x9b\xd7s\xdc\x91BK\xaf',
None,
]
table = pa.table([pa.array(data, type=pa.uuid())], names=["ext"])
print("table schema type:", table.schema.field("ext").type) #
extension<arrow.uuid>
path = Path(tempfile.gettempdir()) / "uuid_ext_test.parquet"
pq.write_table(table, path, store_schema=False)
print("read_schema type:", pq.read_schema(path).field("ext").type)
print("read_table schema type:",
pq.read_table(path).schema.field("ext").type)
### Expected Behavior
read_schema(path) should yield the same type as the table schema (and
read_table), i.e., extension<arrow.uuid>.
### Actual Behavior
read_schema(path) returns fixed_size_binary[16], while the original
table.schema and read_table(path).schema both report extension<arrow.uuid>, so
metadata-based schema inspection drops the extension type.
### Notes
- Observed with the current pyarrow wheel (22.0.0) and current main
sources.
- ParquetFile(...).schema_arrow preserves the extension type; read_schema
does not
### Component(s)
Python, Parquet
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