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lancedb/python/tests/test_expr.py
Shengan Zhang 64aeee84a8 feat(python): support bytes in lit() expressions (#3387) 
Closes #3261.

## Summary

Adds `bytes` to the accepted types of `lancedb.expr.lit()` so that
binary scalars can be used in filter / projection expressions. The
previous attempt in #3235 had to be reverted because DataFusion's SQL
unparser does not support `Binary` / `LargeBinary` scalars, so any
expression containing such a literal would fail in both `to_sql()` and
`__repr__`.

## How

`expr_to_sql_string` now has two paths:

- **Fast path** (no binary literals): delegate to DataFusion's unparser
unchanged.
- **Slow path**: rewrite each `Binary(Some(bytes))` literal in the tree
to a unique string-literal placeholder, run the unparser, then
substitute `'<placeholder>'` with `X'<HEX>'` in the resulting SQL.
`Binary(None)` / `LargeBinary(None)` are rewritten to
`ScalarValue::Null` so the unparser emits plain `NULL`.

This keeps DataFusion as the single source of truth for operator and
function serialization, so binary literals work in every expression node
type the unparser already supports — including nested cases like
`contains(col("data"), lit(b"\xff"))`, `NOT (col == lit(b"..."))`, and
`col.cast(...) == lit(b"...")`.

## Changes

- `rust/lancedb/src/expr/sql.rs`: placeholder-substitution
implementation.
- `rust/lancedb/src/expr.rs`: 4 new unit tests covering binary literals
in equality, compound predicates, scalar function calls, negation, and
`NULL` binary literals.
- `python/src/expr.rs`: `expr_lit` accepts `PyBytes` and produces
`ScalarValue::Binary`.
- `python/Cargo.toml` + `Cargo.lock`: pull in `datafusion-common` for
`ScalarValue`.
- `python/python/lancedb/expr.py`: extend `ExprLike` and `lit()` type
annotations / docstrings with `bytes`.
- `python/python/lancedb/_lancedb.pyi`: update `expr_lit` stub.
- `python/tests/test_expr.py`: unit tests for `to_sql` / `repr` of
binary literals and an integration test against a real `pa.binary()`
column for equality / inequality / compound filters.

## Example

```python
from lancedb.expr import col, lit, func

# Equality against a binary column
col("payload") == lit(b"\xca\xfe")
# Expr((payload = X'CAFE'))

# Nested inside a function call (previously failed)
func("contains", col("data"), lit(b"\xff"))
# Expr(contains(data, X'FF'))

# repr() no longer crashes
repr(lit(b"\xde\xad\xbe\xef"))
# "Expr(X'DEADBEEF')"
```

## Verification

- [x] `cargo test -p lancedb --lib expr::` — 12/12 pass (was 9; +3 new
tests)
- [x] `cargo check --features remote --tests --examples` — clean
- [x] `cargo clippy --features remote --tests --examples` — no warnings
- [x] `cargo fmt --all -- --check` — clean
- [x] `pytest python/tests/test_expr.py` — 76/76 pass (was 74; +2 new
tests)
- [x] `ruff check python` / `ruff format --check python` — clean

## Follow-ups (not in this PR)

Issue #3261 also raises the possibility of a *truncated* `__repr__` for
very large binary literals. This PR keeps `__repr__` exact (it forwards
to `to_sql()`), since truncating display output would diverge from the
SQL that actually gets executed. A display-only truncation could be
added in a follow-up by giving `__repr__` its own renderer.

Made with [Cursor](https://cursor.com)

Co-authored-by: Cursor <cursoragent@cursor.com>
2026-05-14 15:24:52 -07:00

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# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright The LanceDB Authors
"""Tests for the type-safe expression builder API."""
import pytest
import pyarrow as pa
import lancedb
from lancedb.expr import Expr, col, lit, func
# ── unit tests for Expr construction ─────────────────────────────────────────
class TestExprConstruction:
def test_col_returns_expr(self):
e = col("age")
assert isinstance(e, Expr)
def test_lit_int(self):
e = lit(42)
assert isinstance(e, Expr)
def test_lit_float(self):
e = lit(3.14)
assert isinstance(e, Expr)
def test_lit_str(self):
e = lit("hello")
assert isinstance(e, Expr)
def test_lit_bool(self):
e = lit(True)
assert isinstance(e, Expr)
def test_lit_bytes(self):
e = lit(b"\xde\xad\xbe\xef")
assert isinstance(e, Expr)
def test_lit_bytes_empty(self):
e = lit(b"")
assert isinstance(e, Expr)
def test_lit_unsupported_type_raises(self):
with pytest.raises(Exception):
lit([1, 2, 3])
def test_func(self):
e = func("lower", col("name"))
assert isinstance(e, Expr)
assert e.to_sql() == "lower(name)"
def test_func_unknown_raises(self):
with pytest.raises(Exception):
func("not_a_real_function", col("x"))
class TestExprOperators:
def test_eq_operator(self):
e = col("x") == lit(1)
assert isinstance(e, Expr)
assert e.to_sql() == "(x = 1)"
def test_ne_operator(self):
e = col("x") != lit(1)
assert isinstance(e, Expr)
assert e.to_sql() == "(x <> 1)"
def test_lt_operator(self):
e = col("age") < lit(18)
assert isinstance(e, Expr)
assert e.to_sql() == "(age < 18)"
def test_le_operator(self):
e = col("age") <= lit(18)
assert isinstance(e, Expr)
assert e.to_sql() == "(age <= 18)"
def test_gt_operator(self):
e = col("age") > lit(18)
assert isinstance(e, Expr)
assert e.to_sql() == "(age > 18)"
def test_ge_operator(self):
e = col("age") >= lit(18)
assert isinstance(e, Expr)
assert e.to_sql() == "(age >= 18)"
def test_and_operator(self):
e = (col("age") > lit(18)) & (col("status") == lit("active"))
assert isinstance(e, Expr)
assert e.to_sql() == "((age > 18) AND (status = 'active'))"
def test_or_operator(self):
e = (col("a") == lit(1)) | (col("b") == lit(2))
assert isinstance(e, Expr)
assert e.to_sql() == "((a = 1) OR (b = 2))"
def test_invert_operator(self):
e = ~(col("active") == lit(True))
assert isinstance(e, Expr)
assert e.to_sql() == "NOT (active = true)"
def test_add_operator(self):
e = col("x") + lit(1)
assert isinstance(e, Expr)
assert e.to_sql() == "(x + 1)"
def test_sub_operator(self):
e = col("x") - lit(1)
assert isinstance(e, Expr)
assert e.to_sql() == "(x - 1)"
def test_mul_operator(self):
e = col("price") * lit(1.1)
assert isinstance(e, Expr)
assert e.to_sql() == "(price * 1.1)"
def test_div_operator(self):
e = col("total") / lit(2)
assert isinstance(e, Expr)
assert e.to_sql() == "(total / 2)"
def test_radd(self):
e = lit(1) + col("x")
assert isinstance(e, Expr)
assert e.to_sql() == "(1 + x)"
def test_rmul(self):
e = lit(2) * col("x")
assert isinstance(e, Expr)
assert e.to_sql() == "(2 * x)"
def test_coerce_plain_int(self):
# Operators should auto-wrap plain Python values via lit()
e = col("age") > 18
assert isinstance(e, Expr)
assert e.to_sql() == "(age > 18)"
def test_coerce_plain_str(self):
e = col("name") == "alice"
assert isinstance(e, Expr)
assert e.to_sql() == "(name = 'alice')"
class TestExprBytesLiteral:
def test_bytes_to_sql(self):
e = lit(b"\xde\xad\xbe\xef")
assert e.to_sql() == "X'DEADBEEF'"
def test_empty_bytes_to_sql(self):
e = lit(b"")
assert e.to_sql() == "X''"
def test_bytes_repr(self):
e = lit(b"\x01\x02")
assert repr(e) == "Expr(X'0102')"
def test_bytes_equality_expr_sql(self):
e = col("data") == lit(b"\xca\xfe")
assert e.to_sql() == "(data = X'CAFE')"
def test_bytes_ne_expr_sql(self):
e = col("data") != lit(b"\xff")
assert e.to_sql() == "(data <> X'FF')"
def test_bytes_compound_expr_sql(self):
e = (col("data") == lit(b"\x01")) & (col("id") > lit(5))
assert e.to_sql() == "((data = X'01') AND (id > 5))"
def test_bytes_in_function_call(self):
# Regression test: binary literals inside scalar function calls
# used to fail because DataFusion's unparser does not support Binary
# scalars. Now handled via a placeholder-substitution rewrite.
e = func("contains", col("data"), lit(b"\xff"))
assert e.to_sql() == "contains(data, X'FF')"
def test_bytes_in_not(self):
e = ~(col("data") == lit(b"\xff"))
assert e.to_sql() == "NOT (data = X'FF')"
class TestExprStringMethods:
def test_lower(self):
e = col("name").lower()
assert isinstance(e, Expr)
assert e.to_sql() == "lower(name)"
def test_upper(self):
e = col("name").upper()
assert isinstance(e, Expr)
assert e.to_sql() == "upper(name)"
def test_contains(self):
e = col("text").contains(lit("hello"))
assert isinstance(e, Expr)
assert e.to_sql() == "contains(text, 'hello')"
def test_contains_with_str_coerce(self):
e = col("text").contains("hello")
assert isinstance(e, Expr)
assert e.to_sql() == "contains(text, 'hello')"
def test_chained_lower_eq(self):
e = col("name").lower() == lit("alice")
assert isinstance(e, Expr)
assert e.to_sql() == "(lower(name) = 'alice')"
class TestExprCast:
def test_cast_string(self):
e = col("id").cast("string")
assert isinstance(e, Expr)
assert e.to_sql() == "CAST(id AS VARCHAR)"
def test_cast_int32(self):
e = col("score").cast("int32")
assert isinstance(e, Expr)
assert e.to_sql() == "CAST(score AS INTEGER)"
def test_cast_float64(self):
e = col("val").cast("float64")
assert isinstance(e, Expr)
assert e.to_sql() == "CAST(val AS DOUBLE)"
def test_cast_pyarrow_type(self):
e = col("score").cast(pa.int32())
assert isinstance(e, Expr)
assert e.to_sql() == "CAST(score AS INTEGER)"
def test_cast_pyarrow_float64(self):
e = col("val").cast(pa.float64())
assert isinstance(e, Expr)
assert e.to_sql() == "CAST(val AS DOUBLE)"
def test_cast_pyarrow_string(self):
e = col("id").cast(pa.string())
assert isinstance(e, Expr)
assert e.to_sql() == "CAST(id AS VARCHAR)"
def test_cast_pyarrow_and_string_equivalent(self):
# pa.int32() and "int32" should produce equivalent SQL
sql_str = col("x").cast("int32").to_sql()
sql_pa = col("x").cast(pa.int32()).to_sql()
assert sql_str == sql_pa
class TestExprNamedMethods:
def test_eq_method(self):
e = col("x").eq(lit(1))
assert isinstance(e, Expr)
assert e.to_sql() == "(x = 1)"
def test_gt_method(self):
e = col("x").gt(lit(0))
assert isinstance(e, Expr)
assert e.to_sql() == "(x > 0)"
def test_and_method(self):
e = col("x").gt(lit(0)).and_(col("y").lt(lit(10)))
assert isinstance(e, Expr)
assert e.to_sql() == "((x > 0) AND (y < 10))"
def test_or_method(self):
e = col("x").eq(lit(1)).or_(col("x").eq(lit(2)))
assert isinstance(e, Expr)
assert e.to_sql() == "((x = 1) OR (x = 2))"
class TestExprRepr:
def test_repr(self):
e = col("age") > lit(18)
assert repr(e) == "Expr((age > 18))"
def test_to_sql(self):
e = col("age") > 18
assert e.to_sql() == "(age > 18)"
def test_unhashable(self):
e = col("x")
with pytest.raises(TypeError):
{e: 1}
# ── integration tests: end-to-end query against a real table ─────────────────
@pytest.fixture
def simple_table(tmp_path):
db = lancedb.connect(str(tmp_path))
data = pa.table(
{
"id": [1, 2, 3, 4, 5],
"name": ["Alice", "Bob", "Charlie", "alice", "BOB"],
"age": [25, 17, 30, 22, 15],
"score": [1.5, 2.0, 3.5, 4.0, 0.5],
}
)
return db.create_table("test", data)
class TestExprFilter:
def test_simple_gt_filter(self, simple_table):
result = simple_table.search().where(col("age") > lit(20)).to_arrow()
assert result.num_rows == 3 # ages 25, 30, 22
def test_compound_and_filter(self, simple_table):
result = (
simple_table.search()
.where((col("age") > lit(18)) & (col("score") > lit(2.0)))
.to_arrow()
)
assert result.num_rows == 2 # (30, 3.5) and (22, 4.0)
def test_string_equality_filter(self, simple_table):
result = simple_table.search().where(col("name") == lit("Bob")).to_arrow()
assert result.num_rows == 1
def test_or_filter(self, simple_table):
result = (
simple_table.search()
.where((col("age") < lit(18)) | (col("age") > lit(28)))
.to_arrow()
)
assert result.num_rows == 3 # ages 17, 30, 15
def test_coercion_no_lit(self, simple_table):
# Python values should be auto-coerced
result = simple_table.search().where(col("age") > 20).to_arrow()
assert result.num_rows == 3
def test_string_sql_still_works(self, simple_table):
# Backwards compatibility: plain strings still accepted
result = simple_table.search().where("age > 20").to_arrow()
assert result.num_rows == 3
class TestExprProjection:
def test_select_with_expr(self, simple_table):
result = (
simple_table.search()
.select({"double_score": col("score") * lit(2)})
.to_arrow()
)
assert "double_score" in result.schema.names
def test_select_mixed_str_and_expr(self, simple_table):
result = (
simple_table.search()
.select({"id": "id", "double_score": col("score") * lit(2)})
.to_arrow()
)
assert "id" in result.schema.names
assert "double_score" in result.schema.names
def test_select_list_of_columns(self, simple_table):
# Plain list of str still works
result = simple_table.search().select(["id", "name"]).to_arrow()
assert result.schema.names == ["id", "name"]
# ── column name edge cases ────────────────────────────────────────────────────
class TestColNaming:
"""Unit tests verifying that col() preserves identifiers exactly.
Identifiers that need quoting (camelCase, spaces, leading digits, unicode)
are wrapped in backticks to match the lance SQL parser's dialect.
"""
def test_camel_case_preserved_in_sql(self):
# camelCase is quoted with backticks so the case round-trips correctly.
assert col("firstName").to_sql() == "`firstName`"
def test_camel_case_in_expression(self):
assert (col("firstName") > lit(18)).to_sql() == "(`firstName` > 18)"
def test_space_in_name_quoted(self):
assert col("first name").to_sql() == "`first name`"
def test_space_in_expression(self):
assert (col("first name") == lit("A")).to_sql() == "(`first name` = 'A')"
def test_leading_digit_quoted(self):
assert col("2fast").to_sql() == "`2fast`"
def test_unicode_quoted(self):
assert col("名前").to_sql() == "`名前`"
def test_snake_case_unquoted(self):
# Plain snake_case needs no quoting.
assert col("first_name").to_sql() == "first_name"
@pytest.fixture
def special_col_table(tmp_path):
db = lancedb.connect(str(tmp_path))
data = pa.table(
{
"firstName": ["Alice", "Bob", "Charlie"],
"first name": ["A", "B", "C"],
"score": [10, 20, 30],
}
)
return db.create_table("special", data)
class TestColNamingIntegration:
def test_camel_case_filter(self, special_col_table):
result = (
special_col_table.search()
.where(col("firstName") == lit("Alice"))
.to_arrow()
)
assert result.num_rows == 1
assert result["firstName"][0].as_py() == "Alice"
def test_space_in_col_filter(self, special_col_table):
result = (
special_col_table.search().where(col("first name") == lit("B")).to_arrow()
)
assert result.num_rows == 1
def test_camel_case_projection(self, special_col_table):
result = (
special_col_table.search()
.select({"upper_name": col("firstName").upper()})
.to_arrow()
)
assert "upper_name" in result.schema.names
assert sorted(result["upper_name"].to_pylist()) == ["ALICE", "BOB", "CHARLIE"]
# ── bytes / binary column integration tests ───────────────────────────────────
@pytest.fixture
def binary_table(tmp_path):
db = lancedb.connect(str(tmp_path))
data = pa.table(
{
"id": [1, 2, 3],
"payload": pa.array(
[b"\x01\x02", b"\xca\xfe", b"\xff\x00"],
type=pa.binary(),
),
}
)
return db.create_table("binary_test", data)
class TestExprBytesIntegration:
def test_binary_equality_filter(self, binary_table):
result = (
binary_table.search().where(col("payload") == lit(b"\xca\xfe")).to_arrow()
)
assert result.num_rows == 1
assert result["id"][0].as_py() == 2
def test_binary_ne_filter(self, binary_table):
result = (
binary_table.search().where(col("payload") != lit(b"\x01\x02")).to_arrow()
)
assert result.num_rows == 2
def test_binary_compound_filter(self, binary_table):
result = (
binary_table.search()
.where((col("payload") == lit(b"\x01\x02")) | (col("id") == lit(3)))
.to_arrow()
)
assert result.num_rows == 2
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