ClickHouse/dbms/Storages/MergeTree/MergeTreeReadPool.cpp
Ivan 97f2a2213e
Move all folders inside /dbms one level up (#9974)
* Move some code outside dbms/src folder
* Fix paths
2020-04-02 02:51:21 +03:00

301 lines
11 KiB
C++

#include <Storages/MergeTree/MergeTreeReadPool.h>
#include <ext/range.h>
#include <Storages/MergeTree/MergeTreeBaseSelectProcessor.h>
namespace ProfileEvents
{
extern const Event SlowRead;
extern const Event ReadBackoff;
}
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
}
namespace DB
{
MergeTreeReadPool::MergeTreeReadPool(
const size_t threads_, const size_t sum_marks_, const size_t min_marks_for_concurrent_read_,
RangesInDataParts parts_, const MergeTreeData & data_, const PrewhereInfoPtr & prewhere_info_,
const bool check_columns_, const Names & column_names_,
const BackoffSettings & backoff_settings_, size_t preferred_block_size_bytes_,
const bool do_not_steal_tasks_)
: backoff_settings{backoff_settings_}, backoff_state{threads_}, data{data_},
column_names{column_names_}, do_not_steal_tasks{do_not_steal_tasks_},
predict_block_size_bytes{preferred_block_size_bytes_ > 0}, prewhere_info{prewhere_info_}, parts_ranges{parts_}
{
/// parts don't contain duplicate MergeTreeDataPart's.
const auto per_part_sum_marks = fillPerPartInfo(parts_, check_columns_);
fillPerThreadInfo(threads_, sum_marks_, per_part_sum_marks, parts_, min_marks_for_concurrent_read_);
}
MergeTreeReadTaskPtr MergeTreeReadPool::getTask(const size_t min_marks_to_read, const size_t thread, const Names & ordered_names)
{
const std::lock_guard lock{mutex};
/// If number of threads was lowered due to backoff, then will assign work only for maximum 'backoff_state.current_threads' threads.
if (thread >= backoff_state.current_threads)
return nullptr;
if (remaining_thread_tasks.empty())
return nullptr;
const auto tasks_remaining_for_this_thread = !threads_tasks[thread].sum_marks_in_parts.empty();
if (!tasks_remaining_for_this_thread && do_not_steal_tasks)
return nullptr;
/// Steal task if nothing to do and it's not prohibited
const auto thread_idx = tasks_remaining_for_this_thread ? thread : *std::begin(remaining_thread_tasks);
auto & thread_tasks = threads_tasks[thread_idx];
auto & thread_task = thread_tasks.parts_and_ranges.back();
const auto part_idx = thread_task.part_idx;
auto & part = parts_with_idx[part_idx];
auto & marks_in_part = thread_tasks.sum_marks_in_parts.back();
/// Get whole part to read if it is small enough.
auto need_marks = std::min(marks_in_part, min_marks_to_read);
/// Do not leave too little rows in part for next time.
if (marks_in_part > need_marks &&
marks_in_part - need_marks < min_marks_to_read)
need_marks = marks_in_part;
MarkRanges ranges_to_get_from_part;
/// Get whole part to read if it is small enough.
if (marks_in_part <= need_marks)
{
const auto marks_to_get_from_range = marks_in_part;
ranges_to_get_from_part = thread_task.ranges;
marks_in_part -= marks_to_get_from_range;
thread_tasks.parts_and_ranges.pop_back();
thread_tasks.sum_marks_in_parts.pop_back();
if (thread_tasks.sum_marks_in_parts.empty())
remaining_thread_tasks.erase(thread_idx);
}
else
{
/// Loop through part ranges.
while (need_marks > 0 && !thread_task.ranges.empty())
{
auto & range = thread_task.ranges.front();
const size_t marks_in_range = range.end - range.begin;
const size_t marks_to_get_from_range = std::min(marks_in_range, need_marks);
ranges_to_get_from_part.emplace_back(range.begin, range.begin + marks_to_get_from_range);
range.begin += marks_to_get_from_range;
if (range.begin == range.end)
thread_task.ranges.pop_front();
marks_in_part -= marks_to_get_from_range;
need_marks -= marks_to_get_from_range;
}
}
auto curr_task_size_predictor = !per_part_size_predictor[part_idx] ? nullptr
: std::make_unique<MergeTreeBlockSizePredictor>(*per_part_size_predictor[part_idx]); /// make a copy
return std::make_unique<MergeTreeReadTask>(
part.data_part, ranges_to_get_from_part, part.part_index_in_query, ordered_names,
per_part_column_name_set[part_idx], per_part_columns[part_idx], per_part_pre_columns[part_idx],
prewhere_info && prewhere_info->remove_prewhere_column, per_part_should_reorder[part_idx], std::move(curr_task_size_predictor));
}
MarkRanges MergeTreeReadPool::getRestMarks(const IMergeTreeDataPart & part, const MarkRange & from) const
{
MarkRanges all_part_ranges;
/// Inefficient in presence of large number of data parts.
for (const auto & part_ranges : parts_ranges)
{
if (part_ranges.data_part.get() == &part)
{
all_part_ranges = part_ranges.ranges;
break;
}
}
if (all_part_ranges.empty())
throw Exception("Trying to read marks range [" + std::to_string(from.begin) + ", " + std::to_string(from.end) + "] from part '"
+ part.getFullPath() + "' which has no ranges in this query", ErrorCodes::LOGICAL_ERROR);
auto begin = std::lower_bound(all_part_ranges.begin(), all_part_ranges.end(), from, [] (const auto & f, const auto & s) { return f.begin < s.begin; });
if (begin == all_part_ranges.end())
begin = std::prev(all_part_ranges.end());
begin->begin = from.begin;
return MarkRanges(begin, all_part_ranges.end());
}
Block MergeTreeReadPool::getHeader() const
{
return data.getSampleBlockForColumns(column_names);
}
void MergeTreeReadPool::profileFeedback(const ReadBufferFromFileBase::ProfileInfo info)
{
if (backoff_settings.min_read_latency_ms == 0 || do_not_steal_tasks)
return;
if (info.nanoseconds < backoff_settings.min_read_latency_ms * 1000000)
return;
std::lock_guard lock(mutex);
if (backoff_state.current_threads <= 1)
return;
size_t throughput = info.bytes_read * 1000000000 / info.nanoseconds;
if (throughput >= backoff_settings.max_throughput)
return;
if (backoff_state.time_since_prev_event.elapsed() < backoff_settings.min_interval_between_events_ms * 1000000)
return;
backoff_state.time_since_prev_event.restart();
++backoff_state.num_events;
ProfileEvents::increment(ProfileEvents::SlowRead);
LOG_DEBUG(log, std::fixed << std::setprecision(3)
<< "Slow read, event №" << backoff_state.num_events
<< ": read " << info.bytes_read << " bytes in " << info.nanoseconds / 1000000000.0 << " sec., "
<< info.bytes_read * 1000.0 / info.nanoseconds << " MB/s.");
if (backoff_state.num_events < backoff_settings.min_events)
return;
backoff_state.num_events = 0;
--backoff_state.current_threads;
ProfileEvents::increment(ProfileEvents::ReadBackoff);
LOG_DEBUG(log, "Will lower number of threads to " << backoff_state.current_threads);
}
std::vector<size_t> MergeTreeReadPool::fillPerPartInfo(
RangesInDataParts & parts, const bool check_columns)
{
std::vector<size_t> per_part_sum_marks;
Block sample_block = data.getSampleBlock();
for (const auto i : ext::range(0, parts.size()))
{
auto & part = parts[i];
/// Read marks for every data part.
size_t sum_marks = 0;
for (const auto & range : part.ranges)
sum_marks += range.end - range.begin;
per_part_sum_marks.push_back(sum_marks);
auto [required_columns, required_pre_columns, should_reorder] =
getReadTaskColumns(data, part.data_part, column_names, prewhere_info, check_columns);
/// will be used to distinguish between PREWHERE and WHERE columns when applying filter
const auto & required_column_names = required_columns.getNames();
per_part_column_name_set.emplace_back(required_column_names.begin(), required_column_names.end());
per_part_pre_columns.push_back(std::move(required_pre_columns));
per_part_columns.push_back(std::move(required_columns));
per_part_should_reorder.push_back(should_reorder);
parts_with_idx.push_back({ part.data_part, part.part_index_in_query });
if (predict_block_size_bytes)
{
per_part_size_predictor.emplace_back(std::make_unique<MergeTreeBlockSizePredictor>(
part.data_part, column_names, sample_block));
}
else
per_part_size_predictor.emplace_back(nullptr);
}
return per_part_sum_marks;
}
void MergeTreeReadPool::fillPerThreadInfo(
const size_t threads, const size_t sum_marks, std::vector<size_t> per_part_sum_marks,
RangesInDataParts & parts, const size_t min_marks_for_concurrent_read)
{
threads_tasks.resize(threads);
const size_t min_marks_per_thread = (sum_marks - 1) / threads + 1;
for (size_t i = 0; i < threads && !parts.empty(); ++i)
{
auto need_marks = min_marks_per_thread;
while (need_marks > 0 && !parts.empty())
{
const auto part_idx = parts.size() - 1;
RangesInDataPart & part = parts.back();
size_t & marks_in_part = per_part_sum_marks.back();
/// Do not get too few rows from part.
if (marks_in_part >= min_marks_for_concurrent_read &&
need_marks < min_marks_for_concurrent_read)
need_marks = min_marks_for_concurrent_read;
/// Do not leave too few rows in part for next time.
if (marks_in_part > need_marks &&
marks_in_part - need_marks < min_marks_for_concurrent_read)
need_marks = marks_in_part;
MarkRanges ranges_to_get_from_part;
size_t marks_in_ranges = need_marks;
/// Get whole part to read if it is small enough.
if (marks_in_part <= need_marks)
{
ranges_to_get_from_part = part.ranges;
marks_in_ranges = marks_in_part;
need_marks -= marks_in_part;
parts.pop_back();
per_part_sum_marks.pop_back();
}
else
{
/// Loop through part ranges.
while (need_marks > 0)
{
if (part.ranges.empty())
throw Exception("Unexpected end of ranges while spreading marks among threads", ErrorCodes::LOGICAL_ERROR);
MarkRange & range = part.ranges.front();
const size_t marks_in_range = range.end - range.begin;
const size_t marks_to_get_from_range = std::min(marks_in_range, need_marks);
ranges_to_get_from_part.emplace_back(range.begin, range.begin + marks_to_get_from_range);
range.begin += marks_to_get_from_range;
marks_in_part -= marks_to_get_from_range;
need_marks -= marks_to_get_from_range;
if (range.begin == range.end)
part.ranges.pop_front();
}
}
threads_tasks[i].parts_and_ranges.push_back({ part_idx, ranges_to_get_from_part });
threads_tasks[i].sum_marks_in_parts.push_back(marks_in_ranges);
if (marks_in_ranges != 0)
remaining_thread_tasks.insert(i);
}
}
}
}