Example #1
0
 @Override
 public boolean has(final Flag flag) {
   for (final Expr pred : preds) {
     if (flag == Flag.FCS && pred.seqType().mayBeNumber() || pred.has(flag)) return true;
   }
   return false;
 }
Example #2
0
  /**
   * Checks if the predicates are successful for the specified item.
   *
   * @param it item to be checked
   * @param qc query context
   * @return result of check
   * @throws QueryException query exception
   */
  protected final boolean preds(final Item it, final QueryContext qc) throws QueryException {
    if (preds.length == 0) return true;

    // set context value and position
    final Value cv = qc.value;
    try {
      if (qc.scoring) {
        double s = 0;
        for (final Expr p : preds) {
          qc.value = it;
          final Item i = p.test(qc, info);
          if (i == null) return false;
          s += i.score();
        }
        it.score(Scoring.avg(s, preds.length));
      } else {
        for (final Expr p : preds) {
          qc.value = it;
          if (p.test(qc, info) == null) return false;
        }
      }
      return true;
    } finally {
      qc.value = cv;
    }
  }
Example #3
0
  @Override
  public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
    final Expr c = super.optimize(qc, scp);
    if (c != this) return c;

    final int es = exprs.length;
    final ExprList list = new ExprList(es);
    for (int i = 0; i < es; i++) {
      Expr e = exprs[i];
      if (e instanceof CmpG) {
        // merge adjacent comparisons
        while (i + 1 < es && exprs[i + 1] instanceof CmpG) {
          final Expr tmp = ((CmpG) e).union((CmpG) exprs[i + 1], qc, scp);
          if (tmp != null) {
            e = tmp;
            i++;
          } else {
            break;
          }
        }
      }
      // expression will always return true
      if (e == Bln.TRUE) return optPre(Bln.TRUE, qc);
      // skip expression yielding false
      if (e != Bln.FALSE) list.add(e);
    }

    // all arguments return false
    if (list.isEmpty()) return optPre(Bln.FALSE, qc);

    if (es != list.size()) {
      qc.compInfo(OPTREWRITE_X, this);
      exprs = list.finish();
    }
    compFlatten(qc);

    boolean not = true;
    for (final Expr expr : exprs) {
      if (!expr.isFunction(Function.NOT)) {
        not = false;
        break;
      }
    }

    if (not) {
      qc.compInfo(OPTREWRITE_X, this);
      final int el = exprs.length;
      final Expr[] inner = new Expr[el];
      for (int e = 0; e < el; e++) inner[e] = ((Arr) exprs[e]).exprs[0];
      final Expr ex = new And(info, inner).optimize(qc, scp);
      return Function.NOT.get(null, info, ex).optimize(qc, scp);
    }

    // return single expression if it yields a boolean
    return exprs.length == 1 ? compBln(exprs[0], info) : this;
  }
Example #4
0
 /**
  * Prepares this expression for iterative evaluation. The expression can be iteratively evaluated
  * if no predicate or only the first is positional.
  *
  * @return result of check
  */
 protected final boolean posIterator() {
   // check if first predicate is numeric
   if (preds.length == 1) {
     Expr p = preds[0];
     if (p instanceof Int) p = Pos.get(((Int) p).itr(), info);
     pos = p instanceof Pos ? (Pos) p : null;
     last = p.isFunction(Function.LAST);
     preds[0] = p;
   }
   return pos != null || last;
 }
Example #5
0
  /**
   * Merges a single predicate with the root expression and returns the resulting expression, or
   * returns a self reference if the expression cannot be merged. This function is e.g. called by
   * {@link Where#optimize}.
   *
   * @param qc query context
   * @param scp variable scope
   * @param root root expression
   * @return expression
   * @throws QueryException query exception
   */
  public Expr merge(final Expr root, final QueryContext qc, final VarScope scp)
      throws QueryException {

    // only one predicate can be rewritten; root expression must yield nodes
    if (preds.length != 1 || !(root.seqType().type instanceof NodeType)) return this;

    final Expr pred = preds[0];
    // a[.] -> a
    if (pred instanceof Context) return root;

    if (!pred.seqType().mayBeNumber()) {
      // a[b] -> a/b
      if (pred instanceof Path) return Path.get(info, root, pred).optimize(qc, scp);

      if (pred instanceof CmpG) {
        final CmpG cmp = (CmpG) pred;
        final Expr expr1 = cmp.exprs[0], expr2 = cmp.exprs[1];
        // only first operand can depend on context
        if (!expr2.has(Flag.CTX)) {
          Expr path = null;
          // a[. = 'x'] -> a = 'x'
          if (expr1 instanceof Context) path = root;
          // a[text() = 'x'] -> a/text() = 'x'
          if (expr1 instanceof Path) path = Path.get(info, root, expr1).optimize(qc, scp);
          if (path != null) return new CmpG(path, expr2, cmp.op, cmp.coll, cmp.sc, cmp.info);
        }
      }

      if (pred instanceof FTContains) {
        final FTContains cmp = (FTContains) pred;
        final FTExpr ftexpr = cmp.ftexpr;
        // only first operand can depend on context
        if (!ftexpr.has(Flag.CTX)) {
          final Expr expr = cmp.expr;
          Expr path = null;
          // a[. contains text 'x'] -> a contains text 'x'
          if (expr instanceof Context) path = root;
          // [text() contains text 'x'] -> a/text() contains text 'x'
          if (expr instanceof Path) path = Path.get(info, root, expr).optimize(qc, scp);
          if (path != null) return new FTContains(path, ftexpr, cmp.info);
        }
      }
    }
    return this;
  }
Example #6
0
 @Override
 public boolean indexAccessible(final IndexInfo ii) throws QueryException {
   int costs = 0;
   final ExprList el = new ExprList(exprs.length);
   for (final Expr expr : exprs) {
     // check if expression can be rewritten, and if access is not sequential
     if (!expr.indexAccessible(ii)) return false;
     // skip expressions without results
     if (ii.costs == 0) continue;
     costs += ii.costs;
     el.add(ii.expr);
   }
   // use summarized costs for estimation
   ii.costs = costs;
   // no expressions means no costs: expression will later be ignored
   ii.expr = el.size() == 1 ? el.get(0) : new Union(info, el.finish());
   return true;
 }
Example #7
0
 @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;
 }
Example #8
0
  @Override
  public Item item(final QueryContext qc, final InputInfo ii) throws QueryException {
    // compute scoring
    if (qc.scoring) {
      double s = 0;
      boolean f = false;
      for (final Expr expr : exprs) {
        final Item it = expr.ebv(qc, info);
        f |= it.bool(ii);
        s += it.score();
      }
      return Bln.get(f, Scoring.avg(s, exprs.length));
    }

    // standard evaluation
    for (final Expr expr : exprs) {
      if (expr.ebv(qc, info).bool(ii)) return Bln.TRUE;
    }
    return Bln.FALSE;
  }
Example #9
0
  @Override
  public Expr optimize(final QueryContext qc, final VarScope scp) throws QueryException {
    super.optimize(qc, scp);

    final ExprList el = new ExprList(exprs.length);
    for (final Expr ex : exprs) {
      if (ex.isEmpty()) {
        // remove empty operands (return empty sequence if first value is empty)
        if (el.isEmpty()) return optPre(qc);
        qc.compInfo(OPTREMOVE_X_X, this, ex);
      } else {
        el.add(ex);
      }
    }
    // ensure that results are always sorted
    if (el.size() == 1 && iterable) return el.get(0);
    // replace expressions with optimized list
    exprs = el.finish();
    return this;
  }
Example #10
0
 @Override
 public void plan(final FElem plan) {
   for (final Expr p : preds) p.plan(plan);
 }
Example #11
0
 @Override
 public boolean removable(final Var var) {
   for (final Expr p : preds) if (p.uses(var)) return false;
   return true;
 }