Beispiel #1
0
  @Override
  public final Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
    final Value v = initial(qc);
    if (v != null && v.isEmpty() || emptyPath(v)) return optPre(qc);

    // merge descendant steps
    Expr e = mergeSteps(qc);
    if (e == this && v != null && v.type == NodeType.DOC) {
      // check index access
      e = index(qc, v);
      // rewrite descendant to child steps
      if (e == this) e = children(qc, v);
    }
    // recompile path if it has changed
    if (e != this) return e.compile(qc, scp);

    // set atomic type for single attribute steps to speed up predicate tests
    if (root == null && steps.length == 1 && steps[0] instanceof Step) {
      final Step curr = (Step) steps[0];
      if (curr.axis == ATTR && curr.test.kind == Kind.URI_NAME) curr.seqType(SeqType.NOD_ZO);
    }

    // choose best path implementation and set type information
    final Path path = get(info, root, steps);
    path.size = path.size(qc);
    path.seqType = SeqType.get(steps[steps.length - 1].seqType().type, size);
    return path;
  }
Beispiel #2
0
  @Override
  public Value value(final QueryContext ctx) throws QueryException {
    final int o = (int) ctx.resources.output.size();
    final Updates updates = ctx.resources.updates();
    final ContextModifier tmp = updates.mod;
    final TransformModifier pu = new TransformModifier();
    updates.mod = pu;

    try {
      for (final Let fo : copies) {
        final Iter ir = ctx.iter(fo.expr);
        Item i = ir.next();
        if (!(i instanceof ANode) || ir.next() != null) throw UPCOPYMULT.get(fo.info, fo.var.name);

        // copy node to main memory data instance
        i = ((ANode) i).dbCopy(ctx.context.options);
        // add resulting node to variable
        ctx.set(fo.var, i, info);
        pu.addData(i.data());
      }
      final Value v = ctx.value(expr[0]);
      if (!v.isEmpty()) throw BASEX_MOD.get(info);

      updates.prepare();
      updates.apply();
      return ctx.value(expr[1]);
    } finally {
      ctx.resources.output.size(o);
      updates.mod = tmp;
    }
  }
Beispiel #3
0
 @Override
 public Expr compile(final QueryContext qc, final VarScope scp) throws QueryException {
   final Value init = qc.value;
   // never compile predicates with empty sequence as context value (#1016)
   if (init != null && init.isEmpty()) qc.value = null;
   try {
     final int pl = preds.length;
     for (int p = 0; p < pl; ++p) preds[p] = preds[p].compile(qc, scp).optimizeEbv(qc, scp);
     return this;
   } finally {
     qc.value = init;
   }
 }