feat(python): support nested Function Arrow types (#4088)

Teach Python Function authoring to retain the compact V1 grammar for
existing types and emit canonical exact JSON for nested struct
signatures. Adds coverage for recursive struct/list schemas and exact
field properties.
This commit is contained in:
Jack Ye
2026-08-29 23:07:59 -07:00
committed by GitHub
parent 36c142fa2e
commit 101f524e47
2 changed files with 312 additions and 17 deletions
@@ -168,7 +168,7 @@ def test_udf_resolves_module_globals_before_builtins(tmp_path):
udf(module.uses_callable_shadow)
def test_canonical_arrow_type_is_exactly_the_grammar():
def test_canonical_arrow_type_prefers_the_compact_grammar():
from lancedb.functions import _GRAMMAR_PRIMITIVES, _canonical_arrow_type
golden = json.loads(
@@ -181,6 +181,13 @@ def test_canonical_arrow_type_is_exactly_the_grammar():
case["arrow_type"] for case in golden["valid"] if "<" not in case["arrow_type"]
]
assert [name for _, name in _GRAMMAR_PRIMITIVES] == primitives
assert _canonical_arrow_type(pa.list_(pa.field("item", pa.float32(), False))) == (
"list<float32>"
)
assert (
_canonical_arrow_type(pa.large_list(pa.field("item", pa.float32(), False)))
== "large_list<float32>"
)
for outside in [
pa.timestamp("us"),
pa.decimal128(10, 2),
@@ -188,7 +195,6 @@ def test_canonical_arrow_type_is_exactly_the_grammar():
pa.large_binary(),
pa.binary(4),
pa.duration("s"),
pa.struct([pa.field("a", pa.int32())]),
pa.list_(pa.float32(), 0),
pa.list_(pa.timestamp("us")),
]:
@@ -378,14 +384,29 @@ def test_udf_recursion_versus_a_rebound_module_name(tmp_path):
udf(raw_fact)
def test_canonical_arrow_type_rejects_unrepresentable_list_children():
def test_canonical_arrow_type_uses_exact_json_for_list_child_properties():
from lancedb.functions import _canonical_arrow_type
nullable = pa.list_(pa.float32())
assert json.loads(_canonical_arrow_type(nullable)) == {
"type": "list",
"fields": [
{
"name": "item",
"nullable": True,
"type": {"type": "float32"},
}
],
}
named = pa.list_(pa.field("custom", pa.float32(), nullable=False))
assert json.loads(_canonical_arrow_type(named))["fields"][0]["name"] == "custom"
for outside in [
pa.list_(pa.float32()), # pyarrow default: nullable child
pa.list_(pa.field("custom", pa.float32(), nullable=False)),
pa.list_(pa.field("item", pa.float32(), nullable=False, metadata={"k": "v"})),
pa.list_(pa.field("item", pa.float32(), nullable=False), 0),
pa.list_(
pa.field("item", pa.float32(), nullable=False, metadata={"k": "v"}), 3
),
pa.list_(pa.field("custom", pa.float32(), nullable=False), 3),
]:
with pytest.raises(TypeError, match="unsupported Arrow type"):
_canonical_arrow_type(outside)
@@ -395,6 +416,29 @@ def test_canonical_arrow_type_rejects_unrepresentable_list_children():
)
== "fixed_size_list<float32, 3>"
)
fixed = json.loads(_canonical_arrow_type(pa.list_(pa.float32(), 3)))
assert fixed == {
"type": "fixed_size_list",
"fields": [
{
"name": "item",
"nullable": True,
"type": {"type": "float32"},
}
],
"length": 3,
}
large = json.loads(_canonical_arrow_type(pa.large_list(pa.float32())))
assert large["type"] == "large_list"
assert large["fields"][0]["nullable"] is True
for invalid_struct in [
pa.struct([]),
pa.struct([pa.field("a", pa.int32()), pa.field("a", pa.int64())]),
pa.struct([pa.field("", pa.int32())]),
]:
with pytest.raises(TypeError, match="unsupported Arrow type"):
_canonical_arrow_type(invalid_struct)
def _calls_missing(value: int) -> int:
@@ -482,6 +526,105 @@ def test_explicit_arrow_schema_is_deterministic():
assert signature.output.nullable is False
def test_nested_struct_output_uses_canonical_exact_json():
token = pa.struct(
[
pa.field("position", pa.int32(), nullable=False),
pa.field("value", pa.string(), nullable=False),
pa.field("length", pa.int32(), nullable=False),
]
)
analysis = pa.struct(
[
pa.field("normalized_text", pa.string(), nullable=False),
pa.field("has_content", pa.bool_(), nullable=False),
pa.field(
"metrics",
pa.struct(
[
pa.field("character_count", pa.int64(), nullable=False),
pa.field("word_count", pa.int32(), nullable=False),
pa.field("average_word_length", pa.float64(), nullable=False),
]
),
nullable=False,
),
pa.field(
"diagnostics",
pa.struct(
[
pa.field("status", pa.string(), nullable=False),
pa.field(
"normalization",
pa.struct(
[
pa.field("changed", pa.bool_(), nullable=False),
pa.field(
"original_length", pa.int64(), nullable=False
),
]
),
nullable=False,
),
]
),
nullable=False,
),
pa.field(
"token_preview",
pa.list_(pa.field("item", token, nullable=False)),
nullable=False,
),
]
)
@udf(
input_schema=pa.schema([pa.field("text", pa.string(), nullable=False)]),
output_schema=pa.field("analysis", analysis, nullable=False),
)
def analyze(text):
return {"normalized_text": text}
output = analyze.registration_request.signature.output
assert output.kind == "named_struct"
assert [field.name for field in output.fields] == [
"normalized_text",
"has_content",
"metrics",
"diagnostics",
"token_preview",
]
metrics = json.loads(output.fields[2].arrow_type)
assert metrics == {
"type": "struct",
"fields": [
{
"name": "character_count",
"nullable": False,
"type": {"type": "int64"},
},
{
"name": "word_count",
"nullable": False,
"type": {"type": "int32"},
},
{
"name": "average_word_length",
"nullable": False,
"type": {"type": "float64"},
},
],
}
preview = json.loads(output.fields[4].arrow_type)
assert preview["type"] == "list"
assert preview["fields"][0]["type"]["type"] == "struct"
assert [field["name"] for field in preview["fields"][0]["type"]["fields"]] == [
"position",
"value",
"length",
]
def test_annotation_and_explicit_schema_validation_fail_closed():
with pytest.raises(TypeError, match="missing Function annotations"):
@@ -525,6 +668,72 @@ def test_annotation_and_explicit_schema_validation_fail_closed():
def nullable_explicit(value):
return value
for invalid_field in [
pa.field("", pa.int32(), nullable=False),
pa.field("result", pa.int32(), nullable=False, metadata={"k": "v"}),
]:
with pytest.raises(TypeError, match="unsupported Arrow type"):
@udf(
input_schema=pa.schema([pa.field("value", pa.int64())]),
output_schema=pa.schema([invalid_field]),
)
def invalid_explicit_field(value):
return value
with pytest.raises(TypeError, match="unsupported Arrow type"):
@udf(
input_schema=pa.schema(
[pa.field("value", pa.int64(), metadata={"k": "v"})]
),
output_schema=pa.int64(),
)
def input_field_metadata(value):
return value
with pytest.raises(TypeError, match="unsupported Arrow type"):
@udf(
input_schema=pa.schema([pa.field("value", pa.int64())]),
output_schema=pa.field(
"result", pa.int64(), nullable=False, metadata={"k": "v"}
),
)
def scalar_output_field_metadata(value):
return value
struct_type = pa.struct([pa.field("value", pa.int64(), nullable=False)])
with pytest.raises(TypeError, match="unsupported Arrow type"):
@udf(
input_schema=pa.schema([pa.field("value", pa.int64())]),
output_schema=pa.field(
"result", struct_type, nullable=False, metadata={"k": "v"}
),
)
def struct_output_field_metadata(value):
return {"value": value}
for input_schema, output_schema in [
(
pa.schema([pa.field("value", pa.int64())], metadata={"k": "v"}),
pa.int64(),
),
(
pa.schema([pa.field("value", pa.int64())]),
pa.schema(
[pa.field("result", pa.int64(), nullable=False)],
metadata={"k": "v"},
),
),
]:
with pytest.raises(TypeError, match="schema metadata"):
@udf(input_schema=input_schema, output_schema=output_schema)
def schema_metadata(value):
return value
def test_local_function_catalog_operations_are_not_supported(tmp_path):
db = lancedb.connect(tmp_path)