/**
  * Prepares an update request by converting it into an index or delete request or an update
  * response (no action).
  */
 @SuppressWarnings("unchecked")
 public Result prepare(UpdateRequest request, IndexShard indexShard) {
   final GetResult getResult =
       indexShard
           .getService()
           .get(
               request.type(),
               request.id(),
               new String[] {
                 RoutingFieldMapper.NAME,
                 ParentFieldMapper.NAME,
                 TTLFieldMapper.NAME,
                 TimestampFieldMapper.NAME
               },
               true,
               request.version(),
               request.versionType(),
               FetchSourceContext.FETCH_SOURCE,
               false);
   return prepare(indexShard.shardId(), request, getResult);
 }
  /**
   * Prepares an update request by converting it into an index request.
   *
   * <p>TODO: detect a NOOP and return an update response if true
   */
  @SuppressWarnings("unchecked")
  public IndexRequest prepareUpdate(
      DocTableInfo tableInfo,
      ShardUpsertRequest request,
      ShardUpsertRequest.Item item,
      ShardId shardId)
      throws ElasticsearchException {
    IndexService indexService = indicesService.indexServiceSafe(shardId.getIndex());
    IndexShard indexShard = indexService.shardSafe(shardId.id());
    final GetResult getResult =
        indexShard
            .getService()
            .get(
                request.type(),
                item.id(),
                new String[] {RoutingFieldMapper.NAME, ParentFieldMapper.NAME, TTLFieldMapper.NAME},
                true,
                item.version(),
                VersionType.INTERNAL,
                FetchSourceContext.FETCH_SOURCE,
                false);

    if (!getResult.isExists()) {
      throw new DocumentMissingException(
          new ShardId(request.index(), request.shardId()), request.type(), item.id());
    }

    if (getResult.internalSourceRef() == null) {
      // no source, we can't do nothing, through a failure...
      throw new DocumentSourceMissingException(
          new ShardId(request.index(), request.shardId()), request.type(), item.id());
    }

    Tuple<XContentType, Map<String, Object>> sourceAndContent =
        XContentHelper.convertToMap(getResult.internalSourceRef(), true);
    final Map<String, Object> updatedSourceAsMap;
    final XContentType updateSourceContentType = sourceAndContent.v1();
    String routing =
        getResult.getFields().containsKey(RoutingFieldMapper.NAME)
            ? getResult.field(RoutingFieldMapper.NAME).getValue().toString()
            : null;
    String parent =
        getResult.getFields().containsKey(ParentFieldMapper.NAME)
            ? getResult.field(ParentFieldMapper.NAME).getValue().toString()
            : null;

    updatedSourceAsMap = sourceAndContent.v2();

    SymbolToFieldExtractorContext ctx =
        new SymbolToFieldExtractorContext(functions, item.insertValues());

    Map<String, Object> pathsToUpdate = new LinkedHashMap<>();
    Map<String, Object> updatedGeneratedColumns = new LinkedHashMap<>();
    for (int i = 0; i < request.updateColumns().length; i++) {
      /**
       * NOTE: mapping isn't applied. So if an Insert was done using the ES Rest Endpoint the data
       * might be returned in the wrong format (date as string instead of long)
       */
      String columnPath = request.updateColumns()[i];
      Object value =
          SYMBOL_TO_FIELD_EXTRACTOR.convert(item.updateAssignments()[i], ctx).extract(getResult);
      ReferenceInfo referenceInfo = tableInfo.getReferenceInfo(ColumnIdent.fromPath(columnPath));
      if (referenceInfo instanceof GeneratedReferenceInfo) {
        updatedGeneratedColumns.put(columnPath, value);

      } else {
        pathsToUpdate.put(columnPath, value);
      }
    }

    processGeneratedColumns(
        tableInfo,
        pathsToUpdate,
        updatedGeneratedColumns,
        request.validateGeneratedColumns(),
        getResult);

    updateSourceByPaths(updatedSourceAsMap, pathsToUpdate);

    final IndexRequest indexRequest =
        Requests.indexRequest(request.index())
            .type(request.type())
            .id(item.id())
            .routing(routing)
            .parent(parent)
            .source(updatedSourceAsMap, updateSourceContentType)
            .version(getResult.getVersion());
    indexRequest.operationThreaded(false);
    return indexRequest;
  }