1. A method for preparing a relational database for compression by a particular compressor, the method comprising: by a processor, computing an optimum relational dependency transform comprising a set of field dependency relations each containing a predictor field of the relational database and a predictee field of the relational database, the computing comprising computing an optimum branching of a first graph having a node set that is a set of possible predictor fields and predictee fields of the relational database, and having an edge set that comprises possible dependency relations between the predictor fields and the predictee fields, each edge having a weight based on a compression by the particular compressor of a transform of the predictee field based on a defined permutation of the predictor field; by a processor, sorting the fields of the relational database topologically based on a second graph having a node set that is a set of all of the predictor fields and the predictee fields of the optimum relational dependency transform, and having an edge set that comprises the set of field dependency relations of the optimum relational dependency transform; by a processor, for each predictee field in a resulting topologically sorted relational database, transforming the predictee field based on the defined permutation of the predictor field.