* <li>{@link #ANALYZER_SETTINGS_CONTENTS_READING_ANALYZER} - The contents reading analyzer settings field.</li>
 * </ul>
 *
 * This class cannot be instantiated.
 */
public final class FieldNames {
    /** The unique identifier field. */
    public static final String ID = "_id";
    /** The text content field. */
    public static final String TEXT = "text";
    /** The prefix for reading fields. */

        // Test various complex field names
        String[] fieldNames = { "simple_field", "field-with-dashes", "field.with.dots", "field_with_underscores", "fieldWithCamelCase",
                "field with spaces", "field@with#special!chars", "フィールド名", "字段名称", "필드명" };

        for (String fieldName : fieldNames) {
            String encoded = BaseEncoding.base64().encode(fieldName.getBytes(StandardCharsets.UTF_8));

        source.put(FieldNames.TEXT, "test text");
        source.put(FieldNames.DOC_FREQ, 10L);
        source.put(FieldNames.QUERY_FREQ, 5L);
        source.put(FieldNames.USER_BOOST, 1.5f);
        source.put(FieldNames.FIELDS, Arrays.asList("field1"));
        source.put(FieldNames.TAGS, Arrays.asList("tag1"));
        source.put(FieldNames.ROLES, Arrays.asList("role1"));

        map.put(FieldNames.TAGS, item.getTags());
        map.put(FieldNames.ROLES, item.getRoles());
        map.put(FieldNames.LANGUAGES, item.getLanguages());
        map.put(FieldNames.KINDS, Stream.of(item.getKinds()).map(SuggestItem.Kind::toString).toArray());
        map.put(FieldNames.QUERY_FREQ, item.getQueryFreq());
        map.put(FieldNames.DOC_FREQ, item.getDocFreq());
        map.put(FieldNames.USER_BOOST, item.getUserBoost());

            logger.info("Deleting old words: index={}, threshold={}", index, threshold);
        }
        final long start = System.currentTimeMillis();
        final String query = FieldNames.TIMESTAMP + ":[* TO " + threshold.toInstant().toEpochMilli() + "] NOT " + FieldNames.KINDS + ':'
                + SuggestItem.Kind.USER;
        deleteByQuery(index, query);
        return new SuggestDeleteResponse(null, System.currentTimeMillis() - start);
    }

        }
        filterList.add(buildFilterQuery(FieldNames.ROLES, rolesWithDefault));

        if (!fields.isEmpty()) {
            filterList.add(buildFilterQuery(FieldNames.FIELDS, fields));
        }

        if (!kinds.isEmpty()) {
            filterList.add(buildFilterQuery(FieldNames.KINDS, kinds));
        }

        if (filterList.size() > 0) {

        boolQueryBuilder
                .must(QueryBuilders.rangeQuery(FieldNames.TIMESTAMP).lt(time.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli()));

        boolQueryBuilder.must(QueryBuilders.termQuery(FieldNames.KINDS, SuggestItem.Kind.DOCUMENT.toString()));
        boolQueryBuilder.mustNot(QueryBuilders.termQuery(FieldNames.KINDS, SuggestItem.Kind.QUERY.toString()));

        assertNotNull(map);
        assertEquals("", map.get(FieldNames.TEXT)); // Empty string for empty map
        assertEquals(0L, map.get(FieldNames.QUERY_FREQ));
        assertEquals(0L, map.get(FieldNames.DOC_FREQ));
        assertEquals(1.0f, map.get(FieldNames.USER_BOOST));
        assertNotNull(map.get(FieldNames.READING_PREFIX + "0"));
        assertNotNull(map.get(FieldNames.FIELDS));
        assertNotNull(map.get(FieldNames.TAGS));

            flist.add(new FunctionScoreQueryBuilder.FilterFunctionBuilder(QueryBuilders.prefixQuery(FieldNames.TEXT, query),
                    ScoreFunctionBuilders.weightFactorFunction(prefixMatchWeight)));
        }

        flist.add(new FunctionScoreQueryBuilder.FilterFunctionBuilder(ScoreFunctionBuilders.fieldValueFactorFunction(FieldNames.DOC_FREQ)
                .missing(0.1f)

        source.put(FieldNames.TEXT, "test");
        source.put(FieldNames.QUERY_FREQ, 100L);
        source.put(FieldNames.DOC_FREQ, 50L);
        source.put(FieldNames.USER_BOOST, 2.0f);
        source.put(FieldNames.READING_PREFIX + "0", Arrays.asList("reading1"));
        source.put(FieldNames.FIELDS, Arrays.asList("field1"));
        source.put(FieldNames.TAGS, Arrays.asList("tag1"));