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lancedb/python/python/tests/test_hybrid_query.py
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Mohammad Hijjawi 580240278f fix(python): apply the default limit of 10 to sync hybrid queries (#4344)
## Summary

A synchronous hybrid query without an explicit `.limit()` can return up
to 20 rows. The documented default is 10, and `AsyncHybridQuery` already
falls back to `DEFAULT_HYBRID_LIMIT` (10).

In `LanceHybridQueryBuilder`, each sub-query (vector and FTS) falls back
to its own default of 10 rows. The fused result was then sliced with
`limit=None`, i.e. not truncated at all. When the two legs match
different rows, the caller gets the union.

t = db.create_table("t", [{"text": ("dog" if i >= 20 else "cat") + f"
{i}", "vector": [float(i), 0.0]} for i in range(40)])
    t.create_index("text", config=FTS())
len(t.search(query_type="hybrid").vector([0.0,
0.0]).text("dog").to_arrow())
    # before: 20, after: 10

For the same reason, `.offset(n)` without `.limit()` did not raise the
sub-query limits to cover the skipped prefix; that only happened inside
`if self._limit:`.

## Changes

- Use `DEFAULT_HYBRID_LIMIT` when no limit is set, both for the
sub-query limits (`limit + offset`) and for the final slice of the
reranked results, matching `AsyncHybridQuery`.

## Test plan

- [x] New `test_hybrid_query_default_limit` in `test_hybrid_query.py`.
It is the sync counterpart of `test_async_hybrid_query_default_limit`,
plus an `offset()`-without-`limit()` check. It fails before the fix (20
rows) and passes after.
- [x] `pytest python/tests/test_hybrid_query.py
python/tests/test_rerankers.py`
- [x] `ruff format --check` / `ruff check`

I have no local Rust toolchain, so I ran the tests against the released
0.39.0 native module with the changed Python files overlaid. The changed
functions are identical between 0.39.0 and main.
2026-09-28 20:12:00 -05:00

525 lines
17 KiB
Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright The LanceDB Authors
from unittest import mock
import lancedb
from lancedb.query import LanceHybridQueryBuilder
from lancedb.rerankers.rrf import RRFReranker
import pyarrow as pa
import pyarrow.compute as pc
import pytest
import pytest_asyncio
from lancedb.index import BTree, FTS, IvfPq
from lancedb.table import AsyncTable, Table
@pytest.fixture
def sync_table(tmpdir_factory) -> Table:
tmp_path = str(tmpdir_factory.mktemp("data"))
db = lancedb.connect(tmp_path)
data = pa.table(
{
"text": pa.array(["a", "b", "cat", "dog"]),
"vector": pa.array(
[[0.1, 0.1], [2, 2], [-0.1, -0.1], [0.5, -0.5]],
type=pa.list_(pa.float32(), list_size=2),
),
}
)
table = db.create_table("test", data)
table.create_fts_index("text", with_position=False)
return table
@pytest_asyncio.fixture
async def table(tmpdir_factory) -> AsyncTable:
tmp_path = str(tmpdir_factory.mktemp("data"))
db = await lancedb.connect_async(tmp_path)
data = pa.table(
{
"text": pa.array(["a", "b", "cat", "dog"]),
"vector": pa.array(
[[0.1, 0.1], [2, 2], [-0.1, -0.1], [0.5, -0.5]],
type=pa.list_(pa.float32(), list_size=2),
),
}
)
table = await db.create_table("test", data)
await table.create_index("text", config=FTS(with_position=False))
return table
@pytest.mark.asyncio
async def test_async_hybrid_query(table: AsyncTable):
result = await (
table.query().nearest_to([0.0, 0.4]).nearest_to_text("dog").limit(2).to_arrow()
)
assert len(result) == 2
# ensure we get results that would match well for text and vector
assert result["text"].to_pylist() == ["a", "dog"]
# ensure there is no rowid by default
assert "_rowid" not in result
@pytest.mark.asyncio
async def test_async_hybrid_query_with_row_ids(table: AsyncTable):
result = await (
table.query()
.nearest_to([0.0, 0.4])
.nearest_to_text("dog")
.limit(2)
.with_row_id()
.to_arrow()
)
assert len(result) == 2
# ensure we get results that would match well for text and vector
assert result["text"].to_pylist() == ["a", "dog"]
assert result["_rowid"].to_pylist() == [0, 3]
@pytest.mark.asyncio
async def test_async_hybrid_query_filters(table: AsyncTable):
# test that query params are passed down from the regular builder to
# child vector/fts builders
result = await (
table.query()
.where("text not in ('a', 'dog')")
.nearest_to([0.3, 0.3])
.nearest_to_text("*a*")
.distance_type("l2")
.limit(2)
.to_arrow()
)
assert len(result) == 2
# ensure we get results that would match well for text and vector
assert result["text"].to_pylist() == ["cat", "b"]
@pytest.mark.asyncio
async def test_hybrid_query_with_stale_fixed_size_binary_prefilter(
tmpdir_factory,
):
tmp_path = str(tmpdir_factory.mktemp("stale_scalar_prefilter"))
db = await lancedb.connect_async(tmp_path)
def fixed_size_binary(value: int) -> bytes:
return value.to_bytes(16, byteorder="big")
num_rows = 1000
data = pa.table(
{
"space_id": pa.array(
[fixed_size_binary(i) for i in range(num_rows)],
type=pa.binary(16),
),
"text": ["book"] * num_rows,
"vector": pa.array(
[[float(i), float(i)] for i in range(num_rows)],
type=pa.list_(pa.float32(), 2),
),
}
)
table = await db.create_table("test", data)
await table.create_index(
"vector", config=IvfPq(num_partitions=4, num_sub_vectors=2)
)
await table.create_index("space_id", config=BTree())
await table.create_index("text", config=FTS(with_position=False))
# Advance the search indices without advancing the scalar index. This is the
# state that previously let hybrid search use an incomplete scalar prefilter.
await table.add(data)
lance_dataset = await table.to_lance()
lance_dataset.optimize.optimize_indices(index_names=["vector_idx", "text_idx"])
await table.checkout_latest()
scalar_stats = await table.index_stats("space_id_idx")
assert scalar_stats is not None
assert scalar_stats.num_indexed_rows == num_rows
assert scalar_stats.num_unindexed_rows == num_rows
for index_name in ["vector_idx", "text_idx"]:
search_stats = await table.index_stats(index_name)
assert search_stats is not None
assert search_stats.num_indexed_rows == num_rows * 2
assert search_stats.num_unindexed_rows == 0
matching_ids = [5, 10, 15, 20, 25, 30]
literals = [
f"arrow_cast(0x{fixed_size_binary(i).hex()}, 'FixedSizeBinary(16)')"
for i in matching_ids
]
predicate = f"space_id IN ({', '.join(literals)})"
expected_ids = sorted(fixed_size_binary(i) for i in matching_ids for _ in range(2))
vector_query = (
table.query().where(predicate).nearest_to([5.0, 5.0]).limit(num_rows * 2)
)
vector_results = await vector_query.to_arrow()
assert sorted(vector_results["space_id"].to_pylist()) == expected_ids
fts_query = (
table.query().where(predicate).nearest_to_text("book").limit(num_rows * 2)
)
fts_results = await fts_query.to_arrow()
assert sorted(fts_results["space_id"].to_pylist()) == expected_ids
hybrid_results = await (
table.query()
.where(predicate)
.nearest_to([5.0, 5.0])
.nearest_to_text("book")
.limit(num_rows * 2)
.to_arrow()
)
assert sorted(hybrid_results["space_id"].to_pylist()) == expected_ids
@pytest.mark.asyncio
async def test_async_hybrid_query_default_limit(table: AsyncTable):
# add 10 new rows
new_rows = []
for i in range(100):
if i < 2:
new_rows.append({"text": "close_vec", "vector": [0.1, 0.1]})
else:
new_rows.append({"text": "far_vec", "vector": [5 * i, 5 * i]})
await table.add(new_rows)
result = await (
table.query().nearest_to_text("dog").nearest_to([0.1, 0.1]).to_arrow()
)
# assert we got the default limit of 10
assert len(result) == 10
# assert we got the closest vectors and the text searched for
texts = result["text"].to_pylist()
assert texts.count("close_vec") == 2
assert texts.count("dog") == 1
assert texts.count("a") == 1
@pytest.mark.asyncio
async def test_async_hybrid_query_offset(table: AsyncTable):
# The offset window of a hybrid query must be a suffix of the same query
# run without an offset. Skipping the first rows of each sub-query instead
# of the first rows of the fused result silently changes which rows land in
# the window.
full = await (
table.query()
.nearest_to([0.0, 0.4])
.nearest_to_text("dog")
.limit(4)
.with_row_id()
.to_arrow()
)
assert len(full) == 4
second_page = await (
table.query()
.nearest_to([0.0, 0.4])
.nearest_to_text("dog")
.offset(2)
.limit(2)
.with_row_id()
.to_arrow()
)
assert second_page["_rowid"].to_pylist() == full["_rowid"].to_pylist()[2:]
first_page = await (
table.query()
.nearest_to([0.0, 0.4])
.nearest_to_text("dog")
.limit(2)
.with_row_id()
.to_arrow()
)
# Paging through the result must visit every row exactly once: no row
# repeated from the previous page and none dropped between the two.
paged = first_page["_rowid"].to_pylist() + second_page["_rowid"].to_pylist()
assert sorted(paged) == sorted(full["_rowid"].to_pylist())
@pytest.mark.asyncio
async def test_async_hybrid_query_fts_first_default_limit(table: AsyncTable):
# nearest_to() and nearest_to_text() build their new sibling sub-query from
# scratch, and that is the sub-query the default limit ends up on. So the
# side that carries the limit depends on the order the hybrid query was
# built in, and looking at only one side loses the limit for half the ways
# a hybrid query can be written. Without a limit the combined results are
# not truncated at all and the whole union of both candidate lists is
# returned.
await table.add([{"text": "dog", "vector": [50.0 + i, 50.0]} for i in range(10)])
result = await (
table.query().nearest_to_text("dog").nearest_to([0.1, 0.1]).to_arrow()
)
assert len(result) == 10
offset_result = await (
table.query().nearest_to_text("dog").nearest_to([0.1, 0.1]).offset(2).to_arrow()
)
assert len(offset_result) == 10
@pytest.mark.asyncio
async def test_async_hybrid_query_explain_plan_matches_execution(table: AsyncTable):
# Paging rewrites the sub-queries: each one fetches limit + offset rows with
# no offset of its own, and the window is sliced out after fusion. The plans
# have to be built from those rewritten sub-queries, otherwise explain_plan
# and analyze_plan describe a query that is never run.
query = (
table.query().nearest_to([0.0, 0.4]).nearest_to_text("dog").offset(2).limit(2)
)
await query.to_arrow()
plan = await query.explain_plan()
assert [
line.strip() for line in plan.splitlines() if "GlobalLimitExec" in line
] == [
"GlobalLimitExec: skip=0, fetch=4",
"GlobalLimitExec: skip=0, fetch=4",
]
analyzed = await query.analyze_plan()
assert analyzed.count("skip=0, fetch=4") == 2
assert "skip=2" not in analyzed
def test_hybrid_query_offset(sync_table: Table):
# The offset window of a hybrid query must be a suffix of the same query
# run without an offset -- it must not be silently ignored.
full = (
sync_table.search(query_type="hybrid")
.vector([0.0, 0.4])
.text("dog")
.limit(4)
.with_row_id(True)
.to_arrow()
)
assert len(full) == 4
offset_result = (
sync_table.search(query_type="hybrid")
.vector([0.0, 0.4])
.text("dog")
.offset(2)
.limit(2)
.with_row_id(True)
.to_arrow()
)
assert offset_result["_rowid"].to_pylist() == full["_rowid"].to_pylist()[2:]
def test_hybrid_query_default_limit(sync_table: Table):
# The vector and FTS legs match disjoint rows, so fusing their results
# yields more rows than the default limit.
new_rows = []
for i in range(20):
new_rows.append({"text": "close_vec", "vector": [0.1, 0.1]})
new_rows.append({"text": "dog", "vector": [50.0 + i, 50.0 + i]})
sync_table.add(new_rows)
def query():
return (
sync_table.search(query_type="hybrid")
.vector([0.1, 0.1])
.text("dog")
.with_row_id(True)
)
# Like the async hybrid query, the default limit is 10.
result = query().to_arrow()
assert len(result) == 10
# The offset window is taken after the default limit is applied.
full = query().limit(15).to_arrow()
offset_result = query().offset(5).to_arrow()
assert offset_result["_rowid"].to_pylist() == full["_rowid"].to_pylist()[5:]
def test_hybrid_query_minimum_nprobes_zero_raises(sync_table: Table):
# minimum_nprobes(0) must raise the same validation error a plain vector
# query raises, not silently no-op because 0 is falsy.
with pytest.raises(ValueError, match="minimum_nprobes must be greater than 0"):
(
sync_table.search(query_type="hybrid")
.vector([0.0, 0.4])
.text("dog")
.minimum_nprobes(0)
.to_arrow()
)
def test_hybrid_query_distance_range(sync_table: Table):
reranker = RRFReranker(return_score="all")
result = (
sync_table.search(query_type="hybrid")
.vector([0.0, 0.4])
.text("cat and dog")
.distance_range(lower_bound=0.2, upper_bound=0.5)
.rerank(reranker)
.limit(2)
.to_arrow()
)
assert len(result) == 2
print(result)
for dist in result["_distance"]:
if dist.is_valid:
assert 0.2 <= dist.as_py() <= 0.5
def test_hybrid_query_applies_zero_upper_distance_bound(sync_table: Table):
result = (
sync_table.search(query_type="hybrid")
.vector([0.0, 0.4])
.text("elephant")
.distance_range(upper_bound=0.0)
.rerank(RRFReranker(return_score="all"))
.limit(4)
.to_arrow()
)
assert len(result) == 0
@pytest.mark.asyncio
async def test_hybrid_query_distance_range_async(table: AsyncTable):
reranker = RRFReranker(return_score="all")
result = await (
table.query()
.nearest_to([0.0, 0.4])
.nearest_to_text("cat and dog")
.distance_range(lower_bound=0.2, upper_bound=0.5)
.rerank(reranker)
.limit(2)
.to_arrow()
)
assert len(result) == 2
for dist in result["_distance"]:
if dist.is_valid:
assert 0.2 <= dist.as_py() <= 0.5
@pytest.mark.asyncio
async def test_explain_plan(table: AsyncTable):
plan = await (
table.query().nearest_to_text("dog").nearest_to([0.1, 0.1]).explain_plan(True)
)
assert "KNNVectorDistance" in plan
assert "LanceRead" in plan
@pytest.mark.asyncio
async def test_analyze_plan(table: AsyncTable):
res = await (
table.query().nearest_to_text("dog").nearest_to([0.1, 0.1]).analyze_plan()
)
assert "AnalyzeExec" in res
assert "metrics=" in res
def test_hybrid_phrase_query_is_preserved_in_analyze_plan():
table = mock.Mock()
analyzed_queries = []
distributed_metric_modes = []
def capture_query(query, *, distributed_metrics="aggregate"):
analyzed_queries.append(query)
distributed_metric_modes.append(distributed_metrics)
return ""
table._analyze_plan.side_effect = capture_query
(
LanceHybridQueryBuilder(table)
.vector([0.1, 0.2])
.text("puppy runs")
.phrase_query()
.analyze_plan(distributed_metrics="full")
)
assert len(analyzed_queries) == 2
assert analyzed_queries[1].full_text_query.query == '"puppy runs"'
assert distributed_metric_modes == ["full", "full"]
@pytest.fixture
def table_with_id(tmpdir_factory) -> Table:
tmp_path = str(tmpdir_factory.mktemp("data"))
db = lancedb.connect(tmp_path)
data = pa.table(
{
"id": pa.array([1, 2, 3, 4], type=pa.int64()),
"text": pa.array(["a", "b", "cat", "dog"]),
"vector": pa.array(
[[0.1, 0.1], [2, 2], [-0.1, -0.1], [0.5, -0.5]],
type=pa.list_(pa.float32(), list_size=2),
),
}
)
table = db.create_table("test_with_id", data)
table.create_fts_index("text", with_position=False)
return table
def test_hybrid_prefilter_explain_plan(table_with_id: Table):
"""
Verify that the prefilter logic is not inverted in LanceHybridQueryBuilder.
"""
plan_prefilter = (
table_with_id.search(query_type="hybrid")
.vector([0.0, 0.0])
.text("dog")
.where("id = 1", prefilter=True)
.limit(2)
.explain_plan(verbose=True)
)
plan_postfilter = (
table_with_id.search(query_type="hybrid")
.vector([0.0, 0.0])
.text("dog")
.where("id = 1", prefilter=False)
.limit(2)
.explain_plan(verbose=True)
)
# prefilter=True: filter is pushed into the LanceRead scan.
# The FTS sub-plan exposes this as "full_filter=id = Int64(1)" inside LanceRead.
assert "full_filter=id = Int64(1)" in plan_prefilter, (
f"Should push the filter into the scan.\nPlan:\n{plan_prefilter}"
)
# prefilter=False: filter is applied as a separate FilterExec after the search.
# The filter must NOT be embedded in the scan.
assert "full_filter=id = Int64(1)" not in plan_postfilter, (
f"Should NOT push the filter into the scan.\nPlan:\n{plan_postfilter}"
)
def test_normalize_scores():
cases = [
(pa.array([0.1, 0.4]), pa.array([0.0, 1.0])),
(pa.array([2.0, 10.0, 20.0]), pa.array([0.0, 8.0 / 18.0, 1.0])),
(pa.array([0.0, 0.0, 0.0]), pa.array([0.0, 0.0, 0.0])),
(pa.array([10.0, 9.9999999999999]), pa.array([0.0, 0.0])),
]
for input, expected in cases:
for invert in [True, False]:
result = LanceHybridQueryBuilder._normalize_scores(input, invert)
if invert:
expected = pc.subtract(1.0, expected)
assert pc.equal(result, expected), (
f"Expected {expected} but got {result} for invert={invert}"
)