示例#1
0
 @Override
 public Expr optimize(final QueryContext ctx, final VarScope scp) throws QueryException {
   final SeqType s0 = expr[0].type();
   final SeqType s1 = expr[1].type();
   final Type t0 = s0.type;
   final Type t1 = s1.type;
   if (t0.isNumberOrUntyped() && t1.isNumberOrUntyped()) {
     final Occ occ = s0.one() && s1.one() ? Occ.ONE : Occ.ZERO_ONE;
     type = SeqType.get(Calc.type(t0, t1), occ);
   } else if (s0.one() && s1.one()) {
     type = SeqType.ITEM;
   }
   return optPre(oneIsEmpty() ? null : allAreValues() ? item(ctx, info) : this, ctx);
 }
示例#2
0
文件: Preds.java 项目: dirkk/basex
 @Override
 public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
   // number of predicates may change in loop
   for (int p = 0; p < preds.length; p++) {
     final Expr pred = preds[p];
     if (pred instanceof CmpG || pred instanceof CmpV) {
       final Cmp cmp = (Cmp) pred;
       if (cmp.exprs[0].isFunction(Function.POSITION)) {
         final Expr e2 = cmp.exprs[1];
         final SeqType st2 = e2.seqType();
         // position() = last() -> last()
         // position() = $n (numeric) -> $n
         if (e2.isFunction(Function.LAST) || st2.one() && st2.type.isNumber()) {
           if (cmp instanceof CmpG && ((CmpG) cmp).op == OpG.EQ
               || cmp instanceof CmpV && ((CmpV) cmp).op == OpV.EQ) {
             qc.compInfo(OPTWRITE, pred);
             preds[p] = e2;
           }
         }
       }
     } else if (pred instanceof And) {
       if (!pred.has(Flag.FCS)) {
         // replace AND expression with predicates (don't swap position tests)
         qc.compInfo(OPTPRED, pred);
         final Expr[] and = ((Arr) pred).exprs;
         final int m = and.length - 1;
         final ExprList el = new ExprList(preds.length + m);
         for (final Expr e : Arrays.asList(preds).subList(0, p)) el.add(e);
         for (final Expr a : and) {
           // wrap test with boolean() if the result is numeric
           el.add(Function.BOOLEAN.get(null, info, a).optimizeEbv(qc, scp));
         }
         for (final Expr e : Arrays.asList(preds).subList(p + 1, preds.length)) el.add(e);
         preds = el.finish();
       }
     } else if (pred instanceof ANum) {
       final ANum it = (ANum) pred;
       final long i = it.itr();
       if (i == it.dbl()) {
         preds[p] = Pos.get(i, info);
       } else {
         qc.compInfo(OPTREMOVE, this, pred);
         return Empty.SEQ;
       }
     } else if (pred.isValue()) {
       if (pred.ebv(qc, info).bool(info)) {
         qc.compInfo(OPTREMOVE, this, pred);
         preds = Array.delete(preds, p--);
       } else {
         // handle statically known predicates
         qc.compInfo(OPTREMOVE, this, pred);
         return Empty.SEQ;
       }
     }
   }
   return this;
 }
示例#3
0
  /**
   * 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;
  }