Method opt

basex-core/src/main/java/org/basex/query/expr/Intersect.java:36–74

(final CompileContext cc)

  }

  @Override
  Expr opt(final CompileContext cc) throws QueryException {
    flatten(cc);

    // determine type
    SeqType st = Types.GNODE_ZM;
    for(final Expr expr : exprs) {
      final SeqType st2 = expr.seqType();
      if(!st2.zero()) {
        if(!(st2.type instanceof NodeType)) return null;
        st = st.intersect(st2);
        // check for incompatible node types
        if(st == null) return Empty.VALUE;
      }
    }
    exprType.assign(st.union(Occ.ZERO)).data(exprs);

    final ExprList list = new ExprList(exprs.length);
    for(final Expr expr : exprs) {
      if(expr == Empty.VALUE) {
        // empty operand: * intersect () → ()
        return Empty.VALUE;
      } else if(list.contains(expr) && !expr.has(Flag.CNS, Flag.NDT)) {
        // remove duplicates: * intersect * → *
        cc.info(OPTREMOVE_X_X, expr, (Supplier<?>) this::description);
      } else {
        list.add(expr);
      }
    }
    exprs = list.finish();

    final Expr ex = rewrite(Union.class, (invert, ops) ->
      invert ? new Union(info, ops) : new Intersect(info, ops), cc);
    if(ex != null) {
      cc.info(OPTREWRITE_X_X, (Supplier<?>) this::description, ex);
      return ex;
    }
    return null;
  }

  @Override
  And mergePredicates(final Expr[] preds, final CompileContext cc) {