@Override
  public void toData(DataOutput out,
      SerializationContext context) throws IOException {
    out.writeUTF(name);
    out.writeUTF(expression);
    out.writeUTF(fromClause);
    out.writeBoolean(loadEntries);

    if (IndexType.PRIMARY_KEY == indexType) {
      out.writeByte(0);
    } else if (IndexType.HASH == indexType) {
      out.writeByte(1);
    } else {
      out.writeByte(2);
    }


    if (importStr != null) {
      out.writeBoolean(true);
      out.writeUTF(importStr);
    } else {
      out.writeBoolean(false);
    }
  }
This class contains the information needed to create an index It will contain the callback data
between <index></index> invocation
geode-core/src/main/java/org/apache/geode/cache/query/internal/index/IndexCreationData.java