In #816, to avoid cloning a big Vec for use as a hash key, I instead used the hash of the Vec as a key. I guess it's possible to get a hash collision that way and produce the wrong result.
Here I avoid the clone by allocating field selections into an arena allocator. The allocator outlives FieldsInSetCanMerge so we can pass around references to slices, and we can store the reference in the key and the value at the same time.
We already didn't deallocate the Vecs until the FieldsInSetCanMerge struct is dropped so the memory usage is the same.
In #816, to avoid cloning a big
Vecfor use as a hash key, I instead used the hash of the Vec as a key. I guess it's possible to get a hash collision that way and produce the wrong result.Here I avoid the clone by allocating field selections into an arena allocator. The allocator outlives
FieldsInSetCanMergeso we can pass around references to slices, and we can store the reference in the key and the value at the same time.We already didn't deallocate the
Vecs until theFieldsInSetCanMergestruct is dropped so the memory usage is the same.