bkietz commented on a change in pull request #9294:
URL: https://github.com/apache/arrow/pull/9294#discussion_r573793483
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File path: cpp/src/arrow/compute/kernels/scalar_arithmetic_test.cc
##########
@@ -637,5 +637,77 @@ TYPED_TEST(TestBinaryArithmeticFloating, Mul) {
this->AssertBinop(Multiply, "[null, 2.0]", this->MakeNullScalar(), "[null,
null]");
}
+TEST(TestBinaryArithmetic, DispatchBest) {
+ for (std::string name : {"add", "subtract", "multiply", "divide"}) {
+ for (std::string suffix : {"", "_checked"}) {
+ name += suffix;
+
+ CheckDispatchBest(name, {int32(), int32()}, {int32(), int32()});
+ CheckDispatchBest(name, {int32(), null()}, {int32(), int32()});
+ CheckDispatchBest(name, {null(), int32()}, {int32(), int32()});
+
+ CheckDispatchBest(name, {int32(), int8()}, {int32(), int32()});
+ CheckDispatchBest(name, {int32(), int16()}, {int32(), int32()});
+ CheckDispatchBest(name, {int32(), int32()}, {int32(), int32()});
+ CheckDispatchBest(name, {int32(), int64()}, {int64(), int64()});
+
+ CheckDispatchBest(name, {int32(), uint8()}, {int32(), int32()});
+ CheckDispatchBest(name, {int32(), uint16()}, {int32(), int32()});
+ CheckDispatchBest(name, {int32(), uint32()}, {int64(), int64()});
+ CheckDispatchBest(name, {int32(), uint64()}, {int64(), int64()});
+
+ CheckDispatchBest(name, {uint8(), uint8()}, {uint8(), uint8()});
+ CheckDispatchBest(name, {uint8(), uint16()}, {uint16(), uint16()});
+
+ CheckDispatchBest(name, {int32(), float32()}, {float32(), float32()});
+ CheckDispatchBest(name, {float32(), int64()}, {float32(), float32()});
+ CheckDispatchBest(name, {float64(), int32()}, {float64(), float64()});
+
+ CheckDispatchBest(name, {dictionary(int8(), float64()), float64()},
+ {float64(), float64()});
+ CheckDispatchBest(name, {dictionary(int8(), float64()), int16()},
+ {float64(), float64()});
+ }
+ }
+}
+
+TEST(TestBinaryArithmetic, AddWithImplicitCasts) {
+ CheckScalarBinary("add", ArrayFromJSON(int32(), "[0, 1, 2, null]"),
+ ArrayFromJSON(float64(), "[0.25, 0.5, 0.75, 1.0]"),
+ ArrayFromJSON(float64(), "[0.25, 1.5, 2.75, null]"));
+
+ CheckScalarBinary("add", ArrayFromJSON(int8(), "[-16, 0, 16, null]"),
+ ArrayFromJSON(uint32(), "[3, 4, 5, 7]"),
+ ArrayFromJSON(int64(), "[-13, 4, 21, null]"));
+
+ CheckScalarBinary("add",
+ ArrayFromJSON(dictionary(int32(), int32()), "[8, 6, 3,
null, 2]"),
+ ArrayFromJSON(uint32(), "[3, 4, 5, 7, 0]"),
+ ArrayFromJSON(int64(), "[11, 10, 8, null, 2]"));
+
+ CheckScalarBinary("add", ArrayFromJSON(int32(), "[0, 1, 2, null]"),
+ std::make_shared<NullArray>(4),
+ ArrayFromJSON(int32(), "[null, null, null, null]"));
+
+ CheckScalarBinary("add", ArrayFromJSON(dictionary(int32(), int8()), "[0, 1,
2, null]"),
+ ArrayFromJSON(uint32(), "[3, 4, 5, 7]"),
+ ArrayFromJSON(int64(), "[3, 5, 7, null]"));
+}
+
+TEST(TestBinaryArithmetic, AddWithImplicitCastsUint64EdgeCase) {
+ // int64 is as wide as we can promote
+ CheckDispatchBest("add", {int8(), uint64()}, {int64(), int64()});
+
+ // this works sometimes
+ CheckScalarBinary("add", ArrayFromJSON(int8(), "[-1]"),
ArrayFromJSON(uint64(), "[0]"),
+ ArrayFromJSON(int64(), "[-1]"));
+
+ // ... but it can result in impossible implicit casts in the presence of
uint64, since
+ // some uint64 values cannot be cast to int64:
Review comment:
Yes, on balance I think that for now at least it's fine to mark `uint64`
with "I hope you know what you're doing"
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