/**
   * Creates projection list for scan. If the projection contains expressions, then the input
   * references from those expressions are extracted and that list of references becomes the
   * projection list.
   *
   * @param origScan row scan underneath the project
   * @param projRel ProjectRel that we will be creating the projection for
   * @param projectedColumns returns a list of the projected column ordinals, if it is possible to
   *     project
   * @param preserveExprCondition condition that identifies special expressions that should be
   *     preserved in the projection
   * @param defaultExpr expression to be used in the projection if no fields or special columns are
   *     selected
   * @param newProjList returns a new projection RelNode corresponding to a projection that now
   *     references a rowscan that is projecting the input references that were extracted from the
   *     original projection expressions; if the original expression didn't contain expressions,
   *     then this list is returned empty
   * @return true if columns in projection list from the scan need to be renamed
   */
  public boolean createProjectionList(
      FennelRel origScan,
      ProjectRel projRel,
      List<Integer> projectedColumns,
      PushProjector.ExprCondition preserveExprCondition,
      RexNode defaultExpr,
      List<ProjectRel> newProjList) {
    // REVIEW:  what about AnonFields?
    int n = projRel.getChildExps().length;
    RelDataType rowType = origScan.getRowType();
    RelDataType projType = projRel.getRowType();
    RelDataTypeField[] projFields = projType.getFields();
    List<Integer> tempProjList = new ArrayList<Integer>();
    boolean needRename = false;
    for (int i = 0; i < n; ++i) {
      RexNode exp = projRel.getChildExps()[i];
      List<String> origFieldName = new ArrayList<String>();
      Integer projIndex = mapProjCol(exp, origFieldName, rowType);
      if (projIndex == null) {
        // there are expressions in the projection; we need to extract
        // all input references and any special expressions from the
        // projection
        PushProjector pushProject =
            new PushProjector(projRel, null, origScan, preserveExprCondition);
        ProjectRel newProject = pushProject.convertProject(defaultExpr);
        if (newProject == null) {
          // can't do any further projection
          return false;
        }
        newProjList.add(newProject);

        // using the input references we just extracted, it should now
        // be possible to create a projection for the row scan
        needRename =
            createProjectionList(
                origScan,
                (ProjectRel) newProject.getChild(),
                projectedColumns,
                preserveExprCondition,
                defaultExpr,
                newProjList);
        assert (projectedColumns.size() > 0);
        return needRename;
      }
      String projFieldName = projFields[i].getName();
      if (!projFieldName.equals(origFieldName.get(0))) {
        needRename = true;
      }
      tempProjList.add(projIndex);
    }

    // now that we've determined it is possible to project, add the
    // ordinals to the return list
    projectedColumns.addAll(tempProjList);
    return needRename;
  }
 protected Integer mapFieldRef(RexNode exp, List<String> origFieldName, RelDataType rowType) {
   RexInputRef fieldAccess = (RexInputRef) exp;
   origFieldName.add(rowType.getFields()[fieldAccess.getIndex()].getName());
   return fieldAccess.getIndex();
 }
  /**
   * Returns true if a type is a simple cast of another type. It is if the cast type is nullable and
   * the cast is one of the following:
   * <li>x TO x
   * <li>char(n) TO varchar(m)
   * <li>varchar(n) TO varchar(m)
   * <li>x not null TO x nullable
   *
   * @param origType original type passed into the cast operand
   * @param castType type the operand will be casted to
   * @return true if the cast is simple
   */
  private boolean isCastSimple(RelDataType origType, RelDataType castType) {
    SqlTypeName origTypeName = origType.getSqlTypeName();
    SqlTypeName castTypeName = castType.getSqlTypeName();

    if (!(castType.isNullable())) {
      return false;
    }

    Charset origCharset = origType.getCharset();
    Charset castCharset = castType.getCharset();
    if ((origCharset != null) || (castCharset != null)) {
      if ((origCharset == null) || (castCharset == null)) {
        return false;
      }
      if (!origCharset.equals(castCharset)) {
        return false;
      }
    }

    return ((origType == castType)
        || ((origTypeName == SqlTypeName.CHAR) && (castTypeName == SqlTypeName.VARCHAR))
        || ((origTypeName == SqlTypeName.VARCHAR) && (castTypeName == SqlTypeName.VARCHAR))
        || ((origTypeName == castTypeName)
            && (origType.getPrecision() == castType.getPrecision())
            && ((origTypeName != SqlTypeName.DECIMAL)
                || (origType.getScale() == castType.getScale()))
            && (!origType.isNullable() && castType.isNullable())));
  }