return "lang";
                case FessConfig.INDEX_FIELD_has_cache:
                    return "has_cache";
                case FessConfig.INDEX_FIELD_last_modified:
                    return "last_modified";
                case FessConfig.INDEX_FIELD_ANCHOR:
                    return "anchor";
                case FessConfig.INDEX_FIELD_SEGMENT:
                    return "segment";

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

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

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

            @Override

            public String getIndexFieldHost() {
                return "host";
            }

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

            @Override
            public String getIndexFieldMimetype() {
                return "mimetype";
            }

            @Override

            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) {

                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"));

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

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

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

            @Override

    /**
     * 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.
     */

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

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

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

            @Override

        // last_modified
        final Date lastModified = responseData.getLastModified();
        if (lastModified != null) {
            putResultDataBody(dataMap, fessConfig.getIndexFieldLastModified(), lastModified);
            // timestamp
            putResultDataBody(dataMap, fessConfig.getIndexFieldTimestamp(), lastModified);
        } else {
            // timestamp

                Arguments.of((LongGetter) FileEntry::createTime, Long.MAX_VALUE, "max createTime"),

                Arguments.of((LongGetter) FileEntry::lastModified, -2L, "negative lastModified"),
                Arguments.of((LongGetter) FileEntry::lastModified, 42L, "positive lastModified"),

                Arguments.of((LongGetter) FileEntry::lastAccess, 0L, "zero lastAccess"),