void write(const Block & block)
{
if (!block)
return;
size_t rows = block.rowsInFirstColumn();
if (!rows)
return;
StoragePtr destination;
if (!storage.no_destination)
{
destination = storage.context.tryGetTable(storage.destination_database, storage.destination_table);
if (destination)
{
if (destination.get() == &storage)
throw Exception("Destination table is myself. Write will cause infinite loop.", ErrorCodes::INFINITE_LOOP);
/// Проверяем структуру таблицы.
try
{
destination->check(block, true);
}
catch (Exception & e)
{
e.addMessage("(when looking at destination table " + storage.destination_database + "." + storage.destination_table + ")");
throw;
}
}
}
size_t bytes = block.bytes();
/// Если блок уже превышает максимальные ограничения, то пишем минуя буфер.
if (rows > storage.max_thresholds.rows || bytes > storage.max_thresholds.bytes)
{
if (!storage.no_destination)
{
LOG_TRACE(storage.log, "Writing block with " << rows << " rows, " << bytes << " bytes directly.");
storage.writeBlockToDestination(block, destination);
}
return;
}
/// Распределяем нагрузку по шардам по номеру потока.
const auto start_shard_num = Poco::ThreadNumber::get() % storage.num_shards;
/// Перебираем буферы по кругу, пытаясь заблокировать mutex. Не более одного круга.
auto shard_num = start_shard_num;
size_t try_no = 0;
for (; try_no != storage.num_shards; ++try_no)
{
std::unique_lock<std::mutex> lock(storage.buffers[shard_num].mutex, std::try_to_lock_t());
if (lock.owns_lock())
{
insertIntoBuffer(block, storage.buffers[shard_num], std::move(lock));
break;
}
++shard_num;
if (shard_num == storage.num_shards)
shard_num = 0;
}
/// Если так и не удалось ничего сразу заблокировать, то будем ждать на mutex-е.
if (try_no == storage.num_shards)
insertIntoBuffer(block, storage.buffers[start_shard_num], std::unique_lock<std::mutex>(storage.buffers[start_shard_num].mutex));
}
void write(const Block & block) override
{
if (!block)
return;
size_t rows = block.rows();
if (!rows)
return;
StoragePtr destination;
if (!storage.no_destination)
{
destination = storage.context.tryGetTable(storage.destination_database, storage.destination_table);
if (destination)
{
if (destination.get() == &storage)
throw Exception("Destination table is myself. Write will cause infinite loop.", ErrorCodes::INFINITE_LOOP);
/// Check table structure.
try
{
destination->check(block, true);
}
catch (Exception & e)
{
e.addMessage("(when looking at destination table " + storage.destination_database + "." + storage.destination_table + ")");
throw;
}
}
}
size_t bytes = block.bytes();
/// If the block already exceeds the maximum limit, then we skip the buffer.
if (rows > storage.max_thresholds.rows || bytes > storage.max_thresholds.bytes)
{
if (!storage.no_destination)
{
LOG_TRACE(storage.log, "Writing block with " << rows << " rows, " << bytes << " bytes directly.");
storage.writeBlockToDestination(block, destination);
}
return;
}
/// We distribute the load on the shards by the stream number.
const auto start_shard_num = Poco::ThreadNumber::get() % storage.num_shards;
/// We loop through the buffers, trying to lock mutex. No more than one lap.
auto shard_num = start_shard_num;
StorageBuffer::Buffer * least_busy_buffer = nullptr;
std::unique_lock<std::mutex> least_busy_lock;
size_t least_busy_shard_rows = 0;
for (size_t try_no = 0; try_no < storage.num_shards; ++try_no)
{
std::unique_lock<std::mutex> lock(storage.buffers[shard_num].mutex, std::try_to_lock_t());
if (lock.owns_lock())
{
size_t num_rows = storage.buffers[shard_num].data.rows();
if (!least_busy_buffer || num_rows < least_busy_shard_rows)
{
least_busy_buffer = &storage.buffers[shard_num];
least_busy_lock = std::move(lock);
least_busy_shard_rows = num_rows;
}
}
shard_num = (shard_num + 1) % storage.num_shards;
}
/// If you still can not lock anything at once, then we'll wait on mutex.
if (!least_busy_buffer)
insertIntoBuffer(block, storage.buffers[start_shard_num], std::unique_lock<std::mutex>(storage.buffers[start_shard_num].mutex));
else
insertIntoBuffer(block, *least_busy_buffer, std::move(least_busy_lock));
}