3. The method of claim 2 , further comprising: determining, by the computing device, a subspace of an eigenvector representation of the correlation representation, wherein the subspace includes given eigenvectors representative of given variances greater than variances represented by other eigenvectors in the eigenvector representation; and determining, based on the subspace, local weights for the individual costs, wherein the given individual cost is weighted based on a given local weight of the local weights.
2. The method of claim 1 , further comprising: determining, by the computing device, a correlation representation of the individual costs in the plurality of joins indicative of the variability of the given individual cost, wherein the given individual cost is weighted based on the correlation representation.