1. A method executed by a computer, comprising: generating, by the computer, performance characteristic metric vectors representing query execution metrics for a database; given a point in a feature input space that corresponds to a first one of the performance characteristic metric vectors, identifying, by the computer, nearest neighbors of the point and corresponding points in a performance metric feature space; determining, by the computer, a generated point that represents a cluster represented by the corresponding points; and using, by the computer, the performance characteristic metric vectors that correspond to the generated point to predict performance of a query on a first database system having a first configuration of hardware and software and on a second database system having a second configuration of hardware and software, prediction occurring before the query executes on the first database system and before the query executes on the second database system, the second configuration being different than the first configuration.