/**
* Computes the number of results.
*
* @param qc query context (may be @code null)
* @return number of results
*/
private long size(final QueryContext qc) {
final Value rt = initial(qc);
// skip computation if value is not a document node
if (rt == null || rt.type != NodeType.DOC) return -1;
final Data data = rt.data();
// skip computation if no database instance is available, is out-of-date or
// if context does not contain all database nodes
if (data == null || !data.meta.uptodate || data.resources.docs().size() != rt.size()) return -1;
ArrayList<PathNode> nodes = data.paths.root();
long m = 1;
final int sl = steps.length;
for (int s = 0; s < sl; s++) {
final Step curr = axisStep(s);
if (curr != null) {
nodes = curr.nodes(nodes, data);
if (nodes == null) return -1;
} else if (s + 1 == sl) {
m = steps[s].size();
} else {
// stop if a non-axis step is not placed last
return -1;
}
}
long sz = 0;
for (final PathNode pn : nodes) sz += pn.stats.count;
return sz * m;
}
/**
* Returns the root of the current context or {@code null}.
*
* @param ctx query context
* @return root
*/
final Value root(final QueryContext ctx) {
final Value v = ctx != null ? ctx.value : null;
// no root specified: return context, if it does not reference a document
// as e.g. happens in //a(b|c)
if (root == null) return v == null || v.type != NodeType.DOC ? v : null;
// root is value: return root
if (root.isValue()) return (Value) root;
// no root reference, no context: return null
if (!(root instanceof Root) || v == null) return null;
// return context sequence or root of current context
return v.size() == 1 ? Root.root(v) : v;
}