this.relation.baseRelation().orderSpecs(),
this.relation.baseRelation().limit(),
this.relation.baseRelation().limitInverse()).renameColumns(renamer),
s.renameAttributes(renamer),
p.renameAttributes(renamer),
o.renameAttributes(renamer));
}
private boolean isRemovableJoin(Join join) {
for (Attribute side1: join.attributes1()) {
Attribute side2 = join.equalAttribute(side1);