Marten.Events.Projections.Async.Fetcher.fetchNextPage C# (CSharp) Метод

        private async Task<EventPage> fetchNextPage(long lastEncountered)
        {
            using (var conn = _connectionFactory.Create())
            {
                try
                {
                    await conn.OpenAsync(_token).ConfigureAwait(false);

                    var lastPossible = lastEncountered + _options.PageSize;
                    var sql =
                        $@"
select seq_id from {_selector.Events.DatabaseSchemaName}.mt_events where seq_id > :last and seq_id <= :limit and age(transaction_timestamp(), {_selector.Events.DatabaseSchemaName}.mt_events.timestamp) >= :buffer order by seq_id;
{_selector.ToSelectClause(null)} where seq_id > :last and seq_id <= :limit and type = ANY(:types) and age(transaction_timestamp(), {_selector.Events.DatabaseSchemaName}.mt_events.timestamp) >= :buffer order by seq_id;
select min(seq_id) from {_selector.Events.DatabaseSchemaName}.mt_events where seq_id > :limit and type = ANY(:types) and age(transaction_timestamp(), {_selector.Events.DatabaseSchemaName}.mt_events.timestamp) >= :buffer;
select max(seq_id) from {_selector.Events.DatabaseSchemaName}.mt_events where seq_id >= :limit and age(transaction_timestamp(), {_selector.Events.DatabaseSchemaName}.mt_events.timestamp) >= :buffer
".Replace(" as d", "");

                    var cmd = conn.CreateCommand(sql)
                        .With("last", lastEncountered)
                        .With("limit", lastPossible)
                        .With("buffer", _settings.LeadingEdgeBuffer)
                        .With("types", EventTypeNames, NpgsqlDbType.Array | NpgsqlDbType.Varchar);

                    var page = await buildEventPage(lastEncountered, cmd).ConfigureAwait(false);

                    if (page.Count == 0 || page.IsSequential())
                    {
                        return page;
                    }

                    var starting = page;

                    await Task.Delay(250, _token).ConfigureAwait(false);
                    page = await buildEventPage(lastEncountered, cmd).ConfigureAwait(false);
                    while (!page.CanContinueProcessing(starting.Sequences))
                    {
                        starting = page;
                        page = await buildEventPage(lastEncountered, cmd).ConfigureAwait(false);
                    }

                    return page;
                }
                finally
                {
                    conn.Close();
                }
            }
        }