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GH-55404: [C++] Fix coalesce exact dispatch for mixed dictionary types #55405

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Merged
zanmato1984 merged 1 commit into from
Nov 10, 2026
Merged

GH-55404: [C++] Fix coalesce exact dispatch for mixed dictionary types #55405

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52 changes: 52 additions & 0 deletions cpp/src/arrow/compute/expression_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1063,6 +1063,58 @@ TEST(Expression, ExecuteCoalesceOnMixedDecimalTypes) {
AssertDatumsEqual(actual, ArrayFromJSON(decimal128(4, 3), R"(["1.230", "2.345"])"));
}

TEST(Expression, CoalesceDictionaryTypes) {
auto check = [](const ArrayVector& arguments,
const std::shared_ptr<DataType>& output_type,
const std::shared_ptr<Array>& expected) {
FieldVector fields;
std::vector<Expression> args, expected_args;
for (size_t i = 0; i < arguments.size(); ++i) {
auto name = "arg" + std::to_string(i);
fields.push_back(field(name, arguments[i]->type()));
args.push_back(field_ref(name));
expected_args.push_back(arguments[i]->type()->Equals(output_type)
? args.back()
: cast(args.back(), output_type));
}
Schema input_schema(fields);
Expression bound;
ExpectBindsTo(call("coalesce", args), call("coalesce", expected_args), &bound,
input_schema);
ASSERT_NE(bound.type(), nullptr);
EXPECT_TRUE(bound.type()->Equals(output_type));
ASSERT_OK_AND_ASSIGN(auto input, StructArray::Make(arguments, fields));
ASSERT_OK_AND_ASSIGN(auto actual,
ExecuteScalarExpression(bound, input_schema, Datum(input)));
ASSERT_OK(actual.make_array()->ValidateFull());
// Also check logical values when the result stays dictionary-encoded.
ASSERT_OK_AND_ASSIGN(actual, Cast(actual, expected->type()));
AssertDatumsEqual(actual, expected);
};

auto type = dictionary(int8(), int32());
auto left = DictArrayFromJSON(type, "[0, null, 1, null, null]", "[10, 30]");
auto right = DictArrayFromJSON(type, "[null, 0, 1, null, null]", "[20, 40]");
auto third = DictArrayFromJSON(type, "[null, null, null, 0, null]", "[50]");
auto expected = ArrayFromJSON(int32(), "[10, 20, 30, null, null]");
check({left}, type, ArrayFromJSON(int32(), "[10, null, 30, null, null]"));
check({left, right}, type, expected);
check({left, right, third}, type, ArrayFromJSON(int32(), "[10, 20, 30, 50, null]"));

for (const auto& other : {dictionary(int16(), int32()), dictionary(int8(), int64()),
dictionary(int8(), int32(), /*ordered=*/true)}) {
auto output_type = checked_cast<const DictionaryType&>(*other).value_type();
auto mixed_right = DictArrayFromJSON(other, "[null, 0, 1, null, null]", "[20, 40]");
check({left, mixed_right}, output_type,
ArrayFromJSON(output_type, "[10, 20, 30, null, null]"));
check({mixed_right, left}, output_type,
ArrayFromJSON(output_type, "[10, 20, 40, null, null]"));
auto mixed_third = DictArrayFromJSON(other, "[null, null, null, 0, null]", "[50]");
check({left, right, mixed_third}, output_type,
ArrayFromJSON(output_type, "[10, 20, 30, 50, null]"));
}
}

TEST(Expression, BindNestedCall) {
auto expr = add(field_ref("a"),
call("subtract", {call("multiply", {field_ref("b"), field_ref("c")}),
Expand Down
3 changes: 2 additions & 1 deletion cpp/src/arrow/compute/kernels/scalar_if_else.cc
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Expand Up @@ -2816,7 +2816,8 @@ void AddNestedCoalesceKernels(const std::shared_ptr<ScalarFunction>& scalar_func
AddNestedCoalesceKernel<StructType>(scalar_function);
AddNestedCoalesceKernel<DenseUnionType>(scalar_function);
AddNestedCoalesceKernel<SparseUnionType>(scalar_function);
AddNestedCoalesceKernel<DictionaryType>(scalar_function);
AddCoalesceKernel(scalar_function, Type::DICTIONARY,
CoalesceFunctor<DictionaryType>::Exec, AllTypesAreIdentical());
}

void AddChooseKernel(const std::shared_ptr<ScalarFunction>& scalar_function,
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28 changes: 28 additions & 0 deletions cpp/src/arrow/compute/kernels/scalar_if_else_test.cc
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Expand Up @@ -3743,6 +3743,34 @@ TEST(TestCoalesce, DispatchExact) {
CheckDispatchExactFails("coalesce", {decimal128(3, 2), decimal256(4, 1)});
}

TEST(TestCoalesce, DictionaryDispatchExact) {
auto type = dictionary(int8(), int32());
CheckDispatchExact("coalesce", {type});
CheckDispatchExact("coalesce", {type, dictionary(int8(), int32())});
CheckDispatchExact("coalesce", {type, type, type});
for (const auto& other : {dictionary(int16(), int32()), dictionary(int8(), int64()),
dictionary(int8(), int32(), /*ordered=*/true)}) {
CheckDispatchExactFails("coalesce", {type, other});
CheckDispatchExactFails("coalesce", {other, type});
CheckDispatchExactFails("coalesce", {type, type, other});
}
}

TEST(TestCoalesce, DictionaryDispatchBest) {
auto type = dictionary(int8(), int32());
CheckDispatchBest("coalesce", {type}, {type});
CheckDispatchBest("coalesce", {type, dictionary(int8(), int32())}, {type, type});
CheckDispatchBest("coalesce", {type, type, type}, {type, type, type});
for (const auto& other : {dictionary(int16(), int32()), dictionary(int8(), int64()),
dictionary(int8(), int32(), /*ordered=*/true)}) {
auto value_type = checked_cast<const DictionaryType&>(*other).value_type();
CheckDispatchBest("coalesce", {type, other}, {value_type, value_type});
CheckDispatchBest("coalesce", {other, type}, {value_type, value_type});
CheckDispatchBest("coalesce", {type, type, other},
{value_type, value_type, value_type});
}
}

template <typename Type>
class TestChooseNumeric : public ::testing::Test {};
template <typename Type>
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