Re: indexes longer on int than char(40)??

[Ingo Strüwing]

Yes. The pack_keys table option answers your question.

candidateID is not forced unique. Several same values are represented by a single byte in the key file with packed keys. Different values are coded by a byte for the number of key bytes that are the same (from the beginning of the value), a length byte for the rest of the value and the rest of the value. Since the values in the index are sorted, often only the last byte changes. So the packing can be quite efficient.