bug(python): failed to infer column name from the schema

LanceDB version

v0.13.0

What happened?

Query except FTS requires vector column name to be passed in.

Failed to infer vector column at https://github.com/lancedb/lancedb/blob/main/python/python/lancedb/table.py#L1635 the vector_column_name is None without throwing exception.

vector_column_name = inf_vector_column_query(self.schema)

Proposal

• early error out if failed to infer vector column name from schema
• check why schema does not have vector column

Are there known steps to reproduce?

Test dataset

def _test_search_table() -> pa.Table:
    return pa.Table.from_pandas(
        pd.DataFrame(
            {
                "item_id": [1, 2, 3, 4, 5],
                "inner_id": [1, 2, 3, 4, 5],
                "category": ["a", "a", "b", "b", "c"],
                "numeric_int": [2, 5, 3, 1, 4],
                "numeric_float": [0.2, 0.5, 0.3, 0.1, 0.4],
                "category_set": [
                    ["d", "e"],
                    ["d", "f"],
                    ["d", "g"],
                    ["g", "h"],
                    ["h", "i"],
                ],
            }
        )
    )

with search query

result = (
    self._table_inner.search(query_type="hybrid")
    .text(query_text)
    .vector(text_query_encoder([query_text])[0])
    .rerank(reranker=LinearCombinationReranker(text_semantic_search_weight))
    .select([self.INNER_ID_NAME])
    .limit(k)
    .to_arrow()
    .to_pylist()
)

throws exception

in text_semantic_search
    .to_arrow()
../../.conda/envs/dev/lib/python3.11/site-packages/lancedb/query.py:1046: in to_arrow
    vector_results = vector_future.result()
../../.conda/envs/dev/lib/python3.11/concurrent/futures/_base.py:449: in result
    return self.__get_result()
../../.conda/envs/dev/lib/python3.11/concurrent/futures/_base.py:401: in __get_result
    raise self._exception
../../.conda/envs/dev/lib/python3.11/concurrent/futures/thread.py:58: in run
    result = self.fn(*self.args, **self.kwargs)
../../.conda/envs/dev/lib/python3.11/site-packages/lancedb/query.py:647: in to_arrow
    return self.to_batches().read_all()
../../.conda/envs/dev/lib/python3.11/site-packages/lancedb/query.py:678: in to_batches
    result_set = self._table._execute_query(query, batch_size)
../../.conda/envs/dev/lib/python3.11/site-packages/lancedb/table.py:1742: in _execute_query
    return ds.scanner(
../../.conda/envs/dev/lib/python3.11/site-packages/lance/dataset.py:369: in scanner
    builder = builder.nearest(**nearest)
../../.conda/envs/dev/lib/python3.11/site-packages/lance/dataset.py:2441: in nearest
    if self.ds.schema.get_field_index(column) < 0:
pyarrow/types.pxi:3012: in pyarrow.lib.Schema.get_field_index
    ???
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

>   ???
E   TypeError: expected bytes, NoneType found

schema.get_field_index(column) throws exception

pyarrow schema

'inner_id: int64, has_vector: bool, vector: fixed_size_list<item: double>[384], item_id: int64, category: string, numeric_int: int64, numeric_float: double, category_set: list<item: string>'

column is None

(Pdb) pp nearest
{'column': None,
 'k': 3,
 'metric': 'L2',
 'nprobes': 20,
 'q': <vector_values>,
 'refine_factor': None
}

After pass in search(query, vector_column_name), the test passed.