@Override
public VarUsage count(final Var v) {
final VarUsage inPreds = super.count(v), inRoot = root.count(v);
if (inPreds == VarUsage.NEVER) return inRoot;
final long sz = root.size();
return sz >= 0 && sz <= 1 || root.type().zeroOrOne()
? inRoot.plus(inPreds)
: VarUsage.MORE_THAN_ONCE;
}
/**
* Compiles the filter expression, excluding the root node.
*
* @param ctx query context
* @return compiled expression
*/
private Expr opt(final QueryContext ctx) {
// evaluate return type
final SeqType t = root.type();
// determine number of results and type
final long s = root.size();
if (s != -1) {
if (pos != null) {
size = Math.max(0, s + 1 - pos.min) - Math.max(0, s - pos.max);
} else if (last) {
size = s > 0 ? 1 : 0;
}
// no results will remain: return empty sequence
if (size == 0) return optPre(null, ctx);
type = SeqType.get(t.type, size);
} else {
type = SeqType.get(t.type, t.zeroOrOne() ? Occ.ZERO_ONE : Occ.ZERO_MORE);
}
// no numeric predicates.. use simple iterator
if (!super.has(Flag.FCS)) return new IterFilter(this);
// one single position() or last() function specified: return single value
if (preds.length == 1
&& (last || pos != null)
&& root.isValue()
&& t.one()
&& (last || pos.min == 1 && pos.max == 1)) return optPre(root, ctx);
// only choose deterministic and context-independent offsets; e.g., skip:
// (1 to 10)[random:integer(10)] or (1 to 10)[.]
boolean off = false;
if (preds.length == 1) {
final Expr p = preds[0];
final SeqType st = p.type();
off = st.type.isNumber() && st.zeroOrOne() && !p.has(Flag.CTX) && !p.has(Flag.NDT);
if (off) type = SeqType.get(type.type, Occ.ZERO_ONE);
}
// iterator for simple numeric predicate
return off || useIterator() ? new IterPosFilter(this, off) : this;
}
@Override
public Expr optimize(final QueryContext ctx, final VarScope scp) throws QueryException {
final int ar = expr.length - 1;
final Expr f = expr[ar];
final Type t = f.type().type;
if (t instanceof FuncType) {
final FuncType ft = (FuncType) t;
if (ft.args != null && ft.args.length != ar) throw INVARITY.get(info, f, ar);
if (ft.ret != null) type = ft.ret;
}
if (f instanceof XQFunctionExpr) {
// maps can only contain fully evaluated Values, so this is safe
if (allAreValues() && f instanceof Map) return optPre(value(ctx), ctx);
// try to inline the function
if (!(f instanceof FuncItem && comesFrom((FuncItem) f)) && !updating) {
final Expr[] args = Arrays.copyOf(expr, expr.length - 1);
final Expr inl = ((XQFunctionExpr) f).inlineExpr(args, ctx, scp, info);
if (inl != null) return inl;
}
}
return this;
}
