presto-base-jdbc/src/main/java/io/prestosql/plugin/jdbc/StandardColumnMappings.java/StandardColumnMappings/charColumnMapping
class StandardColumnMappings:    public static ColumnMapping charColumnMapping(CharType charType)
    {
        requireNonNull(charType, "charType is null");
        return ColumnMapping.sliceMapping(
                charType,
                (resultSet, columnIndex) -> utf8Slice(CharMatcher.is(' ').trimTrailingFrom(resultSet.getString(columnIndex))),
                charWriteFunction());
    }