@Override
public boolean accept(final ASTVisitor visitor) {
for (final Expr e : preds) {
visitor.enterFocus();
if (!e.accept(visitor)) return false;
visitor.exitFocus();
}
return root.accept(visitor);
}
@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;
}
@Override
public Expr inline(final QueryContext ctx, final VarScope scp, final Var v, final Expr e)
throws QueryException {
final boolean pr = super.inline(ctx, scp, v, e) != null;
final Expr rt = root == null ? null : root.inline(ctx, scp, v, e);
if (rt != null) root = rt;
return pr || rt != null ? optimize(ctx, scp) : null;
}
@Override
public final Expr optimize(final QueryContext ctx, final VarScope scp) throws QueryException {
// invalidate current context value (will be overwritten by filter)
final Value cv = ctx.value;
try {
// return empty root
if (root.isEmpty()) return optPre(null, ctx);
// convert filters without numeric predicates to axis paths
if (root instanceof AxisPath && !super.has(Flag.FCS))
return ((AxisPath) root.copy(ctx, scp)).addPreds(ctx, scp, preds);
// no predicates.. return root; otherwise, do some advanced compilations
return preds.length == 0 ? root : opt(ctx);
} finally {
ctx.value = cv;
}
}
/**
* 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 final int exprSize() {
int sz = 1;
for (final Expr e : preds) sz += e.exprSize();
return sz + root.exprSize();
}
@Override
public final boolean removable(final Var v) {
return root.removable(v) && super.removable(v);
}
@Override
public final boolean has(final Flag flag) {
return root.has(flag) || flag != Flag.CTX && super.has(flag);
}