Let B be a finite, core relational structureand let A be the algebra associated to B, i.e.whose terms are the operations on the universeof B that preserve the relations of B. Weshow that if A generates a so-called arithmetical variety then CSP(B), the constraint satisfaction problem associated to B, is solvable inLogspace; in fact??CSP(B) is expressible insymmetric Datalog. In particular, we obtainthat if??CSP(B) is expressible in Datalog andthe relations of B are invariant under a Maltsevoperation then CSP(B) is in symmetric Datalog.