@Override
public Expr compile(final QueryContext ctx) throws QueryException {
super.compile(ctx);
if (expr[0].isEmpty()) return optPre(null, ctx);
for (int e = 1; e < expr.length; ++e) {
if (expr[e].isEmpty()) {
ctx.compInfo(OPTREMOVE, description(), expr[e]);
expr = Array.delete(expr, e--);
}
}
// results must always be sorted
return expr.length == 1 && iterable ? expr[0] : this;
}
@Override
public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
super.optimize(qc, scp);
final ExprList el = new ExprList(exprs.length);
for (final Expr ex : exprs) {
if (ex.isEmpty()) {
// remove empty operands (return empty sequence if first value is empty)
if (el.isEmpty()) return optPre(qc);
qc.compInfo(OPTREMOVE_X_X, this, ex);
} else {
el.add(ex);
}
}
// ensure that results are always sorted
if (el.size() == 1 && iterable) return el.get(0);
// replace expressions with optimized list
exprs = el.finish();
return this;
}