We allow arrays to have a shorter length than their buffers. Is it also legal for a struct array to have a shorter length than its child arrays? For example, in C++, I can create this today by slicing a struct array:
``` std::shared_ptr<StructArray> my_array = std::dynamic_pointer_cast<StructArray>(array); ASSERT_EQ(my_array->length(), 4); ASSERT_EQ(my_array->field(0)->length(), 4); auto sliced = std::dynamic_pointer_cast<StructArray>(my_array->Slice(2)); ASSERT_EQ(sliced->length(), 2); // Note: StructArray::field pushes its offset and length into the created array ASSERT_EQ(sliced->field(0)->length(), 2); // However, the actually ArrayData objects show the truth ASSERT_EQ(sliced->data()->child_data[0]->length, 4); // Our validator thinks this is ok ASSERT_OK(sliced->ValidateFull()); ``` The only reference I can find in the spec is this: > Struct: a nested layout consisting of a collection of named child fields each > having the same length but possibly different types. This seems to suggest that the C++ implementation is doing something incorrect. I'm asking because I've started to encounter some issues relating to this[1][2] and I'm not sure if the struct array itself is the issue or the fact that we aren't expecting these kinds of struct arrays is the problem. [1] https://github.com/apache/arrow/issues/35450 [2] https://github.com/apache/arrow/issues/35452
