4. A method as claimed in claim 3 wherein the candidate indexes are ordered by request value of importance, the method further comprising, with identification of each candidate index, searching previously identified indexes for an existing index that is similar to the candidate index and choosing from the steps of a) creating a new index, b) reusing the best existing index and c) modifying the best existing index to satisfy the context of the candidate index, choice of steps a, b and c being dependent on match between the candidate index and the best existing index and the value of importance of the requests for which the indexes are identified.
5. A method as claimed in claim 4 wherein a best existing index is determined as a function of match of columns and keys of indexes, with greater weight being given toward match of keys.