final Date lastModified = FessFunctions.parseDate(lastModifiedObj.toString());
            if (lastModified != null) {
                return lastModified;
            }
        } else if (lastModifiedObj instanceof final String[] lastModifieds && lastModifieds.length > 0) {
            final Date lastModified = FessFunctions.parseDate(lastModifieds[0]);
            if (lastModified != null) {

                return "lang,role,label,anchor,virtual_host";
            }

            @Override
            public String getIndexAdminDateFields() {
                return "expires,created,timestamp,last_modified";
            }

            @Override
            public String getIndexAdminIntegerFields() {
                return "";
            }

            @Override

                Set.of(), //
                "{\"timestamp\":{\"order\":\"desc\"}}{\"last_modified\":{\"order\":\"asc\"}}", //
                buildQuery("sort:timestamp.desc sort:last_modified"));
        assertQueryContext(query, Map.of(), //
                Set.of(), //
                "{\"timestamp\":{\"order\":\"desc\"}}{\"last_modified\":{\"order\":\"desc\"}}", //
                buildQuery("sort:timestamp.desc sort:last_modified.desc"));

    /**
     * Field name for URL.
     */
    protected static final String URL = "url";

    /**
     * Field name for last modified timestamp.
     */
    protected static final String LAST_MODIFIED = "lastModified";

    /**
     * Field name for creation time timestamp.
     */
    protected static final String CREATE_TIME = "createTime";

    /**
     * Document type.
     */

                        host:
                          type: string
                          format: hostname
                          example: "fess.codelibs.org"
                        last_modified:
                          type: string
                          format: date-time
                          example: "2017-10-09T22:28:56.000Z"
                        content_length:

            public String getIndexFieldSite() {
                return "site";
            }

            @Override
            public String getIndexFieldLastModified() {
                return "last_modified";
            }

            @Override
            public String getIndexFieldTimestamp() {
                return "timestamp";
            }

            @Override

            "filename", "content", "has_cache", "cache", "digest", "host", "site", "segment", "config_id", "parent_id", "content_length",
            "favorite_count", "click_count", "created", "timestamp", "last_modified", "expires", "virtual_host", "doc_id");

    // ===================================================================================
    // Attribute
    // =========

            public String getIndexFieldSite() {
                return "site";
            }

            @Override
            public String getIndexFieldLastModified() {
                return "last_modified";
            }

            @Override
            public String getIndexFieldTimestamp() {
                return "timestamp";
            }

            @Override

# Field name for language in the index.
index.field.lang=lang
# Field name for cache status in the index.
index.field.has_cache=has_cache
# Field name for last modified date in the index.
index.field.last_modified=last_modified
# Field name for anchor in the index.
index.field.anchor=anchor
# Field name for segment in the index.
index.field.segment=segment
# Field name for role in the index.
index.field.role=role

            public String getIndexFieldSite() {
                return "site";
            }

            @Override
            public String getIndexFieldLastModified() {
                return "last_modified";
            }

            @Override
            public String getIndexFieldTimestamp() {
                return "timestamp";
            }

            @Override