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feat(python): align to_pandas pandas kwargs (#3397)

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## Feature

This PR aligns LanceDB Python `to_pandas()` APIs with Lance pandas
conversion capabilities while keeping LanceDB query-specific semantics
intact.

- Adds `blob_mode` and pandas `**kwargs` support to local table
`to_pandas()`.
- Delegates local `LanceTable.to_pandas()` to Lance dataset
`to_pandas(blob_mode=..., **kwargs)`.
- Keeps remote table `to_pandas()` unsupported with
`NotImplementedError`.
- Allows sync and async query `to_pandas()` to forward pandas kwargs
after LanceDB `flatten` and `timeout` handling.

Why we need this feature:

Users can access Lance blob-aware pandas conversion from LanceDB local
tables and can pass PyArrow pandas conversion options through
table/query APIs without losing existing `flatten` or `timeout`
behavior.

How it works:

The table API exposes a `BlobMode` literal type for `lazy`, `bytes`, and
`descriptions`. Local tables call through to the backing Lance dataset.
Query APIs do not add `blob_mode`; they materialize Arrow results, apply
LanceDB flattening when requested, and then call `to_pandas(**kwargs)`.

## Validation

- `uv run --frozen --extra tests pytest
python/tests/test_table.py::test_table_to_pandas_default_matches_arrow
python/tests/test_table.py::test_table_to_pandas_blob_bytes
python/tests/test_table.py::test_table_to_pandas_kwargs
python/tests/test_query.py::test_query_to_pandas_kwargs
python/tests/test_query.py::test_query_timeout
python/tests/test_remote_db.py::test_table_to_pandas_not_supported`
- `uv run --frozen --extra dev ruff check python/lancedb/table.py
python/lancedb/query.py python/lancedb/remote/table.py
python/tests/test_table.py python/tests/test_query.py
python/tests/test_remote_db.py`
- `uv run --frozen --extra tests pytest python/tests/test_table.py
python/tests/test_query.py python/tests/test_remote_db.py`

Note: `python/uv.lock` was intentionally not committed in this branch.
This commit is contained in:
Yang Cen
2026-05-19 20:05:51 +08:00
committed by GitHub
parent 53c2164b84
commit 5d1c28922a
7 changed files with 186 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
python/python/lancedb/query.py
View File

@@ -718,6 +718,7 @@ class LanceQueryBuilder(ABC):
flatten: Optional[Union[int, bool]] = None,
*,
timeout: Optional[timedelta] = None,
**kwargs,
) -> "pd.DataFrame":
"""
Execute the query and return the results as a pandas DataFrame.
@@ -735,9 +736,12 @@ class LanceQueryBuilder(ABC):
timeout: Optional[timedelta]
The maximum time to wait for the query to complete.
If None, wait indefinitely.
**kwargs
Forwarded to pyarrow.Table.to_pandas after query execution and
optional flattening.
"""
tbl = flatten_columns(self.to_arrow(timeout=timeout), flatten)
return tbl.to_pandas()
return tbl.to_pandas(**kwargs)
@abstractmethod
def to_arrow(self, *, timeout: Optional[timedelta] = None) -> pa.Table:
@@ -2352,6 +2356,7 @@ class AsyncQueryBase(object):
self,
flatten: Optional[Union[int, bool]] = None,
timeout: Optional[timedelta] = None,
**kwargs,
) -> "pd.DataFrame":
"""
Execute the query and collect the results into a pandas DataFrame.
@@ -2384,10 +2389,13 @@ class AsyncQueryBase(object):
The maximum time to wait for the query to complete.
If not specified, no timeout is applied. If the query does not
complete within the specified time, an error will be raised.
**kwargs
Forwarded to pyarrow.Table.to_pandas after query execution and
optional flattening.
"""
return (
flatten_columns(await self.to_arrow(timeout=timeout), flatten)
).to_pandas()
).to_pandas(**kwargs)
async def to_polars(
self,
@@ -3389,6 +3397,7 @@ class BaseQueryBuilder(object):
self,
flatten: Optional[Union[int, bool]] = None,
timeout: Optional[timedelta] = None,
**kwargs,
) -> "pd.DataFrame":
"""
Execute the query and collect the results into a pandas DataFrame.
@@ -3421,8 +3430,11 @@ class BaseQueryBuilder(object):
The maximum time to wait for the query to complete.
If not specified, no timeout is applied. If the query does not
complete within the specified time, an error will be raised.
**kwargs
Forwarded to pyarrow.Table.to_pandas after query execution and
optional flattening.
"""
return LOOP.run(self._inner.to_pandas(flatten, timeout))
return LOOP.run(self._inner.to_pandas(flatten, timeout, **kwargs))
def to_polars(
self,

4
python/python/lancedb/remote/table.py
View File

@@ -40,7 +40,7 @@ from lancedb.embeddings import EmbeddingFunctionRegistry
from lancedb.table import _normalize_progress
from ..query import LanceVectorQueryBuilder, LanceQueryBuilder, LanceTakeQueryBuilder
from ..table import AsyncTable, IndexStatistics, Query, Table, Tags
from ..table import AsyncTable, BlobMode, IndexStatistics, Query, Table, Tags
from ..types import BaseTokenizerType
@@ -101,7 +101,7 @@ class RemoteTable(Table):
"""to_arrow() is not yet supported on LanceDB cloud."""
raise NotImplementedError("to_arrow() is not yet supported on LanceDB cloud.")
def to_pandas(self):
def to_pandas(self, blob_mode: BlobMode = "lazy", **kwargs):
"""to_pandas() is not yet supported on LanceDB cloud."""
raise NotImplementedError("to_pandas() is not yet supported on LanceDB cloud.")

60
python/python/lancedb/table.py
View File

@@ -87,6 +87,8 @@ from .util import (
)
from .index import lang_mapping
BlobMode = Literal["lazy", "bytes", "descriptions"]
_MODEL_BACKED_TOKENIZER_PREFIXES = ("jieba", "lindera")
_MODEL_BACKED_TOKENIZER_ERRORS = (
"unknown base tokenizer",
@@ -760,14 +762,22 @@ class Table(ABC):
"""
raise NotImplementedError
def to_pandas(self) -> "pandas.DataFrame":
def to_pandas(self, blob_mode: BlobMode = "lazy", **kwargs) -> "pandas.DataFrame":
"""Return the table as a pandas DataFrame.
Parameters
----------
blob_mode: str, default "lazy"
Controls how blob columns are returned for backends that support
Lance blob-aware pandas conversion.
**kwargs
Forwarded to PyArrow / Lance pandas conversion.
Returns
-------
pd.DataFrame
"""
return self.to_arrow().to_pandas()
return self.to_arrow().to_pandas(**kwargs)
@abstractmethod
def to_arrow(self) -> pa.Table:
@@ -2183,14 +2193,27 @@ class LanceTable(Table):
"""Return the first n rows of the table."""
return LOOP.run(self._table.head(n))
def to_pandas(self) -> "pd.DataFrame":
def to_pandas(self, blob_mode: BlobMode = "lazy", **kwargs) -> "pd.DataFrame":
"""Return the table as a pandas DataFrame.
Parameters
----------
blob_mode: str, default "lazy"
Controls how Lance blob columns are returned.
**kwargs
Forwarded to Lance pandas conversion.
Returns
-------
pd.DataFrame
"""
return self.to_arrow().to_pandas()
if blob_mode == "lazy" and (
self._namespace_client is not None
or get_uri_scheme(self._dataset_path) == "memory"
):
return self.to_arrow().to_pandas(**kwargs)
return self.to_lance().to_pandas(blob_mode=blob_mode, **kwargs)
def to_arrow(self) -> pa.Table:
"""Return the table as a pyarrow Table.
@@ -3945,14 +3968,39 @@ class AsyncTable:
"""
return AsyncQuery(self._inner.query())
async def to_pandas(self) -> "pd.DataFrame":
async def _to_lance(self, **kwargs) -> lance.LanceDataset:
try:
import lance
except ImportError:
raise ImportError(
"The lance library is required to use this function. "
"Please install with `pip install pylance`."
)
return lance.dataset(
await self.uri(),
version=await self.version(),
storage_options=await self.latest_storage_options(),
**kwargs,
)
async def to_pandas(self, blob_mode: BlobMode = "lazy", **kwargs) -> "pd.DataFrame":
"""Return the table as a pandas DataFrame.
Parameters
----------
blob_mode: str, default "lazy"
Controls how Lance blob columns are returned.
**kwargs
Forwarded to PyArrow / Lance pandas conversion.
Returns
-------
pd.DataFrame
"""
return (await self.to_arrow()).to_pandas()
if blob_mode == "lazy":
return (await self.to_arrow()).to_pandas(**kwargs)
return (await self._to_lance()).to_pandas(blob_mode=blob_mode, **kwargs)
async def to_arrow(self) -> pa.Table:
"""Return the table as a pyarrow Table.

16
python/python/tests/test_query.py
View File

@@ -165,6 +165,22 @@ def test_offset(table):
assert len(results_with_offset.to_pandas()) == 1
@pytest.mark.asyncio
async def test_query_to_pandas_kwargs(table, table_async):
sync_df = (
LanceVectorQueryBuilder(table, [0, 0], "vector")
.select(["id"])
.limit(1)
.to_pandas(split_blocks=True)
)
assert sync_df["id"].tolist() == [1]
async_df = await (
table_async.query().select(["id"]).limit(2).to_pandas(split_blocks=True)
)
assert async_df["id"].tolist() == [1, 2]
def test_order_by_plain_query(mem_db):
table = mem_db.create_table(
"test_order_by",

19
python/python/tests/test_remote_db.py
View File

@@ -269,6 +269,25 @@ def test_table_unimplemented_functions():
table.to_pandas()
def test_table_to_pandas_not_supported():
def handler(request):
if request.path == "/v1/table/test/create/?mode=create":
request.send_response(200)
request.send_header("Content-Type", "application/json")
request.end_headers()
request.wfile.write(b"{}")
else:
request.send_response(404)
request.end_headers()
with mock_lancedb_connection(handler) as db:
table = db.create_table("test", [{"id": 1}])
with pytest.raises(NotImplementedError):
table.to_pandas()
with pytest.raises(NotImplementedError):
table.to_pandas(blob_mode="bytes", split_blocks=True)
def test_table_add_in_threadpool():
def handler(request):
if request.path == "/v1/table/test/insert/":

79
python/python/tests/test_table.py
View File

@@ -47,6 +47,85 @@ def test_basic(mem_db: DBConnection):
assert table.to_arrow() == expected_data
def test_table_to_pandas_default_matches_arrow(tmp_db: DBConnection):
pd = pytest.importorskip("pandas")
data = pa.table({"id": [1, 2], "text": ["one", "two"]})
table = tmp_db.create_table("test_to_pandas_old_call", data=data)
expected = data.to_pandas()
pd.testing.assert_frame_equal(table.to_pandas(), expected)
def test_table_to_pandas_blob_bytes(tmp_db: DBConnection):
pytest.importorskip("lance")
data = pa.table(
{
"id": pa.array([1, 2], pa.int64()),
"blob": pa.array([b"hello", b"world"], pa.large_binary()),
},
schema=pa.schema(
[
pa.field("id", pa.int64()),
pa.field(
"blob", pa.large_binary(), metadata={"lance-encoding:blob": "true"}
),
]
),
)
table = tmp_db.create_table("test_to_pandas_blob_bytes", data=data)
df = table.to_pandas(blob_mode="bytes")
assert df["blob"].tolist() == [b"hello", b"world"]
def test_table_to_pandas_kwargs(tmp_db: DBConnection):
pd = pytest.importorskip("pandas")
data = pa.table({"id": pa.array([1, 2], pa.int64())})
table = tmp_db.create_table("test_to_pandas_kwargs", data=data)
df = table.to_pandas(types_mapper=pd.ArrowDtype)
assert str(df["id"].dtype) == "int64[pyarrow]"
@pytest.mark.asyncio
async def test_async_table_to_pandas_blob_bytes(tmp_db_async: AsyncConnection):
pytest.importorskip("lance")
data = pa.table(
{
"id": pa.array([1, 2], pa.int64()),
"blob": pa.array([b"hello", b"world"], pa.large_binary()),
},
schema=pa.schema(
[
pa.field("id", pa.int64()),
pa.field(
"blob", pa.large_binary(), metadata={"lance-encoding:blob": "true"}
),
]
),
)
table = await tmp_db_async.create_table(
"test_async_to_pandas_blob_bytes", data=data
)
df = await table.to_pandas(blob_mode="bytes")
assert df["blob"].tolist() == [b"hello", b"world"]
@pytest.mark.asyncio
async def test_async_table_to_pandas_kwargs(tmp_db_async: AsyncConnection):
pd = pytest.importorskip("pandas")
data = pa.table({"id": pa.array([1, 2], pa.int64())})
table = await tmp_db_async.create_table("test_async_to_pandas_kwargs", data=data)
df = await table.to_pandas(types_mapper=pd.ArrowDtype)
assert str(df["id"].dtype) == "int64[pyarrow]"
def test_create_table_infers_large_int_vectors(mem_db: DBConnection):
data = [{"vector": [0, 300]}]