Yang Cen 927ba2c948 fix(python): route blob query pandas through scanner (#3491)
## Bug Fix

### What is the bug?
`QueryBuilder.to_pandas(blob_mode="descriptions")` could still fall back
to `self.to_arrow()` for query outputs with blob columns. Custom query
subclasses or wrappers can have `to_arrow()` behavior that is not
compatible with pandas blob-description conversion, which can surface as
low-level Arrow/list-batch conversion failures.

### What issues or incorrect behavior does the bug cause?
Callers need to carry local `to_pandas` or plain-scan adapter special
casing for blob descriptions, and scanner-only kwargs such as row
addresses and fragment selection are not represented in LanceDB query
state.

### How does this PR fix the problem?
This PR routes blob-output query `to_pandas()` through the Lance scanner
path for `lazy`, `bytes`, and `descriptions` modes when the query is a
scanner-backed plain scan. For `blob_mode="descriptions"` with
`flatten`, it collects scanner Arrow/table output, applies LanceDB
`flatten_columns`, and converts to pandas from there. Non-plain blob
query shapes now fail with a clear unsupported error instead of falling
into subclass `to_arrow()` behavior.

It also adds Python query state and builder methods for scanner-only
plain-scan parameters:

- `with_row_address()` for `_rowaddr`
- `with_fragments(...)` for Lance fragment objects
- `fragment_ids([...])` as a convenience wrapper that resolves IDs to
Lance fragments

## Validation

- `cd python && uv run --no-sync ruff format --check
python/lancedb/query.py python/tests/test_query.py`
- `cd python && uv run --no-sync ruff check python/lancedb/query.py
python/tests/test_query.py`

Targeted pytest was intentionally not run locally per maintainer
request.
2026-06-04 14:03:33 +08:00
2023-03-17 18:15:19 -07:00
2025-03-10 09:01:23 -07:00

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