static Map<Integer, Integer> identityMap(int count) {
    ImmutableMap.Builder<Integer, Integer> builder = ImmutableMap.builder();
    for (int i = 0; i < count; i++) {
      builder.put(i, i);
    }
    return builder.build();
  }
Projects all {@code input} output fields plus the additional expressions.

@param input        Input relational expression
@param additionalExprs Additional expressions and names
@return the new Project
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/rules/HiveRelDecorrelator.java