ClickHouse/dbms/DataStreams/ParallelAggregatingBlockInputStream.cpp

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#include <DataStreams/BlocksListBlockInputStream.h>
#include <DataStreams/NativeBlockInputStream.h>
#include <DataStreams/MergingAggregatedMemoryEfficientBlockInputStream.h>
#include <DataStreams/ParallelAggregatingBlockInputStream.h>
#include <Common/ClickHouseRevision.h>
namespace ProfileEvents
{
extern const Event ExternalAggregationMerge;
}
namespace DB
{
ParallelAggregatingBlockInputStream::ParallelAggregatingBlockInputStream(
const BlockInputStreams & inputs, const BlockInputStreamPtr & additional_input_at_end,
const Aggregator::Params & params_, bool final_, size_t max_threads_, size_t temporary_data_merge_threads_)
: params(params_), aggregator(params),
final(final_), max_threads(std::min(inputs.size(), max_threads_)), temporary_data_merge_threads(temporary_data_merge_threads_),
keys_size(params.keys_size), aggregates_size(params.aggregates_size),
handler(*this), processor(inputs, additional_input_at_end, max_threads, handler)
{
children = inputs;
if (additional_input_at_end)
children.push_back(additional_input_at_end);
}
Block ParallelAggregatingBlockInputStream::getHeader() const
{
return aggregator.getHeader(final);
}
void ParallelAggregatingBlockInputStream::cancel(bool kill)
{
if (kill)
is_killed = true;
bool old_val = false;
if (!is_cancelled.compare_exchange_strong(old_val, true, std::memory_order_seq_cst, std::memory_order_relaxed))
return;
if (!executed)
processor.cancel(kill);
}
Block ParallelAggregatingBlockInputStream::readImpl()
{
if (!executed)
{
Aggregator::CancellationHook hook = [&]() { return this->isCancelled(); };
aggregator.setCancellationHook(hook);
execute();
if (isCancelledOrThrowIfKilled())
return {};
if (!aggregator.hasTemporaryFiles())
{
/** If all partially-aggregated data is in RAM, then merge them in parallel, also in RAM.
*/
impl = aggregator.mergeAndConvertToBlocks(many_data, final, max_threads);
}
else
{
/** If there are temporary files with partially-aggregated data on the disk,
* then read and merge them, spending the minimum amount of memory.
*/
ProfileEvents::increment(ProfileEvents::ExternalAggregationMerge);
const auto & files = aggregator.getTemporaryFiles();
BlockInputStreams input_streams;
for (const auto & file : files.files)
{
temporary_inputs.emplace_back(std::make_unique<TemporaryFileStream>(file->path()));
input_streams.emplace_back(temporary_inputs.back()->block_in);
}
LOG_TRACE(log, "Will merge " << files.files.size() << " temporary files of size "
<< (files.sum_size_compressed / 1048576.0) << " MiB compressed, "
<< (files.sum_size_uncompressed / 1048576.0) << " MiB uncompressed.");
impl = std::make_unique<MergingAggregatedMemoryEfficientBlockInputStream>(
input_streams, params, final, temporary_data_merge_threads, temporary_data_merge_threads);
}
executed = true;
}
Block res;
if (isCancelledOrThrowIfKilled() || !impl)
return res;
return impl->read();
}
void ParallelAggregatingBlockInputStream::Handler::onBlock(Block & block, size_t thread_num)
{
parent.aggregator.executeOnBlock(block, *parent.many_data[thread_num],
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parent.threads_data[thread_num].key_columns, parent.threads_data[thread_num].aggregate_columns, parent.no_more_keys);
parent.threads_data[thread_num].src_rows += block.rows();
parent.threads_data[thread_num].src_bytes += block.bytes();
}
void ParallelAggregatingBlockInputStream::Handler::onFinishThread(size_t thread_num)
{
if (!parent.isCancelled() && parent.aggregator.hasTemporaryFiles())
{
/// Flush data in the RAM to disk. So it's easier to unite them later.
auto & data = *parent.many_data[thread_num];
if (data.isConvertibleToTwoLevel())
data.convertToTwoLevel();
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if (!data.empty())
parent.aggregator.writeToTemporaryFile(data);
}
}
void ParallelAggregatingBlockInputStream::Handler::onFinish()
{
if (!parent.isCancelled() && parent.aggregator.hasTemporaryFiles())
{
/// It may happen that some data has not yet been flushed,
/// because at the time of `onFinishThread` call, no data has been flushed to disk, and then some were.
for (auto & data : parent.many_data)
{
if (data->isConvertibleToTwoLevel())
data->convertToTwoLevel();
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if (!data->empty())
parent.aggregator.writeToTemporaryFile(*data);
}
}
}
void ParallelAggregatingBlockInputStream::Handler::onException(std::exception_ptr & exception, size_t thread_num)
{
parent.exceptions[thread_num] = exception;
parent.cancel(false);
}
void ParallelAggregatingBlockInputStream::execute()
{
many_data.resize(max_threads);
exceptions.resize(max_threads);
for (size_t i = 0; i < max_threads; ++i)
threads_data.emplace_back(keys_size, aggregates_size);
LOG_TRACE(log, "Aggregating");
Stopwatch watch;
for (auto & elem : many_data)
elem = std::make_shared<AggregatedDataVariants>();
processor.process();
processor.wait();
rethrowFirstException(exceptions);
if (isCancelledOrThrowIfKilled())
return;
double elapsed_seconds = watch.elapsedSeconds();
size_t total_src_rows = 0;
size_t total_src_bytes = 0;
for (size_t i = 0; i < max_threads; ++i)
{
size_t rows = many_data[i]->size();
LOG_TRACE(log, std::fixed << std::setprecision(3)
<< "Aggregated. " << threads_data[i].src_rows << " to " << rows << " rows"
<< " (from " << threads_data[i].src_bytes / 1048576.0 << " MiB)"
<< " in " << elapsed_seconds << " sec."
<< " (" << threads_data[i].src_rows / elapsed_seconds << " rows/sec., "
<< threads_data[i].src_bytes / elapsed_seconds / 1048576.0 << " MiB/sec.)");
total_src_rows += threads_data[i].src_rows;
total_src_bytes += threads_data[i].src_bytes;
}
LOG_TRACE(log, std::fixed << std::setprecision(3)
<< "Total aggregated. " << total_src_rows << " rows (from " << total_src_bytes / 1048576.0 << " MiB)"
<< " in " << elapsed_seconds << " sec."
<< " (" << total_src_rows / elapsed_seconds << " rows/sec., " << total_src_bytes / elapsed_seconds / 1048576.0 << " MiB/sec.)");
/// If there was no data, and we aggregate without keys, we must return single row with the result of empty aggregation.
/// To do this, we pass a block with zero rows to aggregate.
if (total_src_rows == 0 && params.keys_size == 0 && !params.empty_result_for_aggregation_by_empty_set)
aggregator.executeOnBlock(children.at(0)->getHeader(), *many_data[0],
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threads_data[0].key_columns, threads_data[0].aggregate_columns, no_more_keys);
}
}