@Override
protected final Expr compPath(final QueryContext ctx) throws QueryException {
for (final Expr s : steps) checkUp(s, ctx);
// merge two axis paths
if (root instanceof AxisPath) {
Expr[] st = ((AxisPath) root).steps;
root = ((AxisPath) root).root;
for (final Expr s : steps) st = Array.add(st, s);
steps = st;
// refresh root context
ctx.compInfo(OPTMERGE);
ctx.value = root(ctx);
}
final AxisStep s = voidStep(steps);
if (s != null) COMPSELF.thrw(input, s);
for (int i = 0; i != steps.length; ++i) {
final Expr e = steps[i].comp(ctx);
if (!(e instanceof AxisStep)) return e;
steps[i] = e;
}
optSteps(ctx);
// retrieve data reference
final Data data = ctx.data();
if (data != null && ctx.value.type == NodeType.DOC) {
// check index access
Expr e = index(ctx, data);
// check children path rewriting
if (e == this) e = children(ctx, data);
// return optimized expression
if (e != this) return e.comp(ctx);
}
// analyze if result set can be cached - no predicates/variables...
cache = root != null && !uses(Use.VAR);
// if applicable, use iterative evaluation
final Path path = finish(ctx);
// heuristics: wrap with filter expression if only one result is expected
return size() != 1 ? path : new Filter(input, this, Pos.get(1, size(), input)).comp2(ctx);
}
