Implemented proper flush before returning position in getPos().
This ensures Parquet's recorded offsets match actual file layout.
RESULT: Still fails with same 78-byte EOF error!
FINDINGS:
- Flush IS happening (17 chunks created)
- Last getPos() returns 1252
- 8 more bytes written after last getPos() (writes #466-470)
- Final file size: 1260 bytes (correct!)
- But Parquet expects: 1338 bytes (1260 + 78)
The 8 bytes after last getPos() are the footer length + magic bytes.
But this doesn't explain the 78-byte discrepancy.
Need to investigate further - the issue is more complex than
simple flush timing.