* @param id the parent document ID whose children should be deleted
     * @return the number of child documents that were deleted
     */
    public long deleteChildDocument(final SearchEngineClient searchEngineClient, final String id) {
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        return searchEngineClient.deleteByQuery(fessConfig.getIndexDocumentUpdateIndex(),

                return 0;
            }
        };
        ComponentUtil.register(client, "searchEngineClient");

        final String id = "001";

        assertEquals(1, indexingHelper.deleteChildDocument(client, id));
        assertEquals("fess.update", resultMap.get("index"));
        assertEquals(id, resultMap.get("id"));
        assertEquals("parent_id", resultMap.get("field"));
    }