Type Definition datafusion::physical_expr::OrderingEquivalentClass

pub type OrderingEquivalentClass = EquivalentClass<Vec<PhysicalSortExpr, Global>>;

LexOrdering stores the lexicographical ordering for a schema. OrderingEquivalentClass keeps track of different alternative orderings than can describe the schema. For instance, for the table below |a|b|c|d| |1|4|3|1| |2|3|3|2| |3|1|2|2| |3|2|1|3| both vec![a ASC, b ASC] and vec![c DESC, d ASC] describe the ordering of the table. For this case, we say that vec![a ASC, b ASC], and vec![c DESC, d ASC] are ordering equivalent.