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ReadFromMergeTree.cpp
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ReadFromMergeTree.cpp
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#include <Processors/QueryPlan/ReadFromMergeTree.h>
#include <IO/Operators.h>
#include <Interpreters/Context.h>
#include <Interpreters/ExpressionAnalyzer.h>
#include <Interpreters/InterpreterSelectQuery.h>
#include <Interpreters/TreeRewriter.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTIdentifier.h>
#include <Parsers/ASTSelectQuery.h>
#include <Processors/ConcatProcessor.h>
#include <Processors/Merges/AggregatingSortedTransform.h>
#include <Processors/Merges/CollapsingSortedTransform.h>
#include <Processors/Merges/GraphiteRollupSortedTransform.h>
#include <Processors/Merges/MergingSortedTransform.h>
#include <Processors/Merges/ReplacingSortedTransform.h>
#include <Processors/Merges/SummingSortedTransform.h>
#include <Processors/Merges/VersionedCollapsingTransform.h>
#include <Processors/QueryPlan/PartsSplitter.h>
#include <Processors/Sources/NullSource.h>
#include <Processors/Transforms/ExpressionTransform.h>
#include <Processors/Transforms/FilterTransform.h>
#include <Processors/Transforms/ReverseTransform.h>
#include <QueryPipeline/QueryPipelineBuilder.h>
#include <Storages/MergeTree/MergeTreeDataSelectExecutor.h>
#include <Storages/MergeTree/MergeTreeReadPool.h>
#include <Storages/MergeTree/MergeTreePrefetchedReadPool.h>
#include <Storages/MergeTree/MergeTreeReadPoolInOrder.h>
#include <Storages/MergeTree/MergeTreeReadPoolParallelReplicas.h>
#include <Storages/MergeTree/MergeTreeReadPoolParallelReplicasInOrder.h>
#include <Storages/MergeTree/MergeTreeSource.h>
#include <Storages/MergeTree/RangesInDataPart.h>
#include <Storages/MergeTree/RequestResponse.h>
#include <Storages/VirtualColumnUtils.h>
#include <base/sort.h>
#include <Poco/Logger.h>
#include <Common/JSONBuilder.h>
#include <Common/isLocalAddress.h>
#include <Common/logger_useful.h>
#include <Parsers/parseIdentifierOrStringLiteral.h>
#include <Parsers/ExpressionListParsers.h>
#include <algorithm>
#include <functional>
#include <iterator>
#include <limits>
#include <memory>
#include <numeric>
#include <queue>
#include <stdexcept>
#include <unordered_map>
using namespace DB;
namespace
{
template <typename Container, typename Getter>
size_t countPartitions(const Container & parts, Getter get_partition_id)
{
if (parts.empty())
return 0;
String cur_partition_id = get_partition_id(parts[0]);
size_t unique_partitions = 1;
for (size_t i = 1; i < parts.size(); ++i)
{
if (get_partition_id(parts[i]) != cur_partition_id)
{
++unique_partitions;
cur_partition_id = get_partition_id(parts[i]);
}
}
return unique_partitions;
}
size_t countPartitions(const RangesInDataParts & parts_with_ranges)
{
auto get_partition_id = [](const RangesInDataPart & rng) { return rng.data_part->info.partition_id; };
return countPartitions(parts_with_ranges, get_partition_id);
}
size_t countPartitions(const MergeTreeData::DataPartsVector & prepared_parts)
{
auto get_partition_id = [](const MergeTreeData::DataPartPtr data_part) { return data_part->info.partition_id; };
return countPartitions(prepared_parts, get_partition_id);
}
}
namespace ProfileEvents
{
extern const Event SelectedParts;
extern const Event SelectedRanges;
extern const Event SelectedMarks;
}
namespace DB
{
namespace ErrorCodes
{
extern const int INDEX_NOT_USED;
extern const int LOGICAL_ERROR;
extern const int TOO_MANY_ROWS;
extern const int CANNOT_PARSE_TEXT;
}
static MergeTreeReaderSettings getMergeTreeReaderSettings(
const ContextPtr & context, const SelectQueryInfo & query_info)
{
const auto & settings = context->getSettingsRef();
return
{
.read_settings = context->getReadSettings(),
.save_marks_in_cache = true,
.checksum_on_read = settings.checksum_on_read,
.read_in_order = query_info.input_order_info != nullptr,
.apply_deleted_mask = settings.apply_deleted_mask,
.use_asynchronous_read_from_pool = settings.allow_asynchronous_read_from_io_pool_for_merge_tree
&& (settings.max_streams_to_max_threads_ratio > 1 || settings.max_streams_for_merge_tree_reading > 1),
.enable_multiple_prewhere_read_steps = settings.enable_multiple_prewhere_read_steps,
};
}
static const PrewhereInfoPtr & getPrewhereInfoFromQueryInfo(const SelectQueryInfo & query_info)
{
return query_info.projection ? query_info.projection->prewhere_info
: query_info.prewhere_info;
}
static bool checkAllPartsOnRemoteFS(const RangesInDataParts & parts)
{
for (const auto & part : parts)
{
if (!part.data_part->isStoredOnRemoteDisk())
return false;
}
return true;
}
/// build sort description for output stream
static void updateSortDescriptionForOutputStream(
DataStream & output_stream, const Names & sorting_key_columns, const int sort_direction, InputOrderInfoPtr input_order_info, PrewhereInfoPtr prewhere_info)
{
/// Updating sort description can be done after PREWHERE actions are applied to the header.
/// Aftert PREWHERE actions are applied, column names in header can differ from storage column names due to aliases
/// To mitigate it, we're trying to build original header and use it to deduce sorting description
/// TODO: this approach is fragile, it'd be more robust to update sorting description for the whole plan during plan optimization
Block original_header = output_stream.header.cloneEmpty();
if (prewhere_info)
{
if (prewhere_info->prewhere_actions)
{
FindOriginalNodeForOutputName original_column_finder(prewhere_info->prewhere_actions);
for (auto & column : original_header)
{
const auto * original_node = original_column_finder.find(column.name);
if (original_node)
column.name = original_node->result_name;
}
}
if (prewhere_info->row_level_filter)
{
FindOriginalNodeForOutputName original_column_finder(prewhere_info->row_level_filter);
for (auto & column : original_header)
{
const auto * original_node = original_column_finder.find(column.name);
if (original_node)
column.name = original_node->result_name;
}
}
}
SortDescription sort_description;
const Block & header = output_stream.header;
for (const auto & sorting_key : sorting_key_columns)
{
const auto it = std::find_if(
original_header.begin(), original_header.end(), [&sorting_key](const auto & column) { return column.name == sorting_key; });
if (it == original_header.end())
break;
const size_t column_pos = std::distance(original_header.begin(), it);
sort_description.emplace_back((header.begin() + column_pos)->name, sort_direction);
}
if (!sort_description.empty())
{
if (input_order_info)
{
output_stream.sort_scope = DataStream::SortScope::Stream;
const size_t used_prefix_of_sorting_key_size = input_order_info->used_prefix_of_sorting_key_size;
if (sort_description.size() > used_prefix_of_sorting_key_size)
sort_description.resize(used_prefix_of_sorting_key_size);
}
else
output_stream.sort_scope = DataStream::SortScope::Chunk;
}
output_stream.sort_description = std::move(sort_description);
}
void ReadFromMergeTree::AnalysisResult::checkLimits(const Settings & settings, const SelectQueryInfo & query_info_) const
{
/// Do not check number of read rows if we have reading
/// in order of sorting key with limit.
/// In general case, when there exists WHERE clause
/// it's impossible to estimate number of rows precisely,
/// because we can stop reading at any time.
SizeLimits limits;
if (settings.read_overflow_mode == OverflowMode::THROW
&& settings.max_rows_to_read
&& !query_info_.input_order_info)
limits = SizeLimits(settings.max_rows_to_read, 0, settings.read_overflow_mode);
SizeLimits leaf_limits;
if (settings.read_overflow_mode_leaf == OverflowMode::THROW
&& settings.max_rows_to_read_leaf
&& !query_info_.input_order_info)
leaf_limits = SizeLimits(settings.max_rows_to_read_leaf, 0, settings.read_overflow_mode_leaf);
if (limits.max_rows || leaf_limits.max_rows)
{
/// Fail fast if estimated number of rows to read exceeds the limit
size_t total_rows_estimate = selected_rows;
if (query_info_.limit > 0 && total_rows_estimate > query_info_.limit)
{
total_rows_estimate = query_info_.limit;
}
limits.check(total_rows_estimate, 0, "rows (controlled by 'max_rows_to_read' setting)", ErrorCodes::TOO_MANY_ROWS);
leaf_limits.check(
total_rows_estimate, 0, "rows (controlled by 'max_rows_to_read_leaf' setting)", ErrorCodes::TOO_MANY_ROWS);
}
}
ReadFromMergeTree::ReadFromMergeTree(
MergeTreeData::DataPartsVector parts_,
std::vector<AlterConversionsPtr> alter_conversions_,
Names real_column_names_,
Names virt_column_names_,
const MergeTreeData & data_,
const SelectQueryInfo & query_info_,
StorageSnapshotPtr storage_snapshot_,
ContextPtr context_,
size_t max_block_size_,
size_t num_streams_,
bool sample_factor_column_queried_,
std::shared_ptr<PartitionIdToMaxBlock> max_block_numbers_to_read_,
Poco::Logger * log_,
MergeTreeDataSelectAnalysisResultPtr analyzed_result_ptr_,
bool enable_parallel_reading)
: SourceStepWithFilter(DataStream{.header = MergeTreeSelectProcessor::transformHeader(
storage_snapshot_->getSampleBlockForColumns(real_column_names_),
getPrewhereInfoFromQueryInfo(query_info_),
data_.getPartitionValueType(),
virt_column_names_)})
, reader_settings(getMergeTreeReaderSettings(context_, query_info_))
, prepared_parts(std::move(parts_))
, alter_conversions_for_parts(std::move(alter_conversions_))
, real_column_names(std::move(real_column_names_))
, virt_column_names(std::move(virt_column_names_))
, data(data_)
, query_info(query_info_)
, prewhere_info(getPrewhereInfoFromQueryInfo(query_info))
, actions_settings(ExpressionActionsSettings::fromContext(context_))
, storage_snapshot(std::move(storage_snapshot_))
, metadata_for_reading(storage_snapshot->getMetadataForQuery())
, context(std::move(context_))
, block_size{
.max_block_size_rows = max_block_size_,
.preferred_block_size_bytes = context->getSettingsRef().preferred_block_size_bytes,
.preferred_max_column_in_block_size_bytes = context->getSettingsRef().preferred_max_column_in_block_size_bytes}
, requested_num_streams(num_streams_)
, sample_factor_column_queried(sample_factor_column_queried_)
, max_block_numbers_to_read(std::move(max_block_numbers_to_read_))
, log(log_)
, analyzed_result_ptr(analyzed_result_ptr_)
, is_parallel_reading_from_replicas(enable_parallel_reading)
{
if (sample_factor_column_queried)
{
/// Only _sample_factor virtual column is added by ReadFromMergeTree
/// Other virtual columns are added by MergeTreeSelectProcessor.
auto type = std::make_shared<DataTypeFloat64>();
output_stream->header.insert({type->createColumn(), type, "_sample_factor"});
}
if (is_parallel_reading_from_replicas)
{
all_ranges_callback = context->getMergeTreeAllRangesCallback();
read_task_callback = context->getMergeTreeReadTaskCallback();
}
const auto & settings = context->getSettingsRef();
if (settings.max_streams_for_merge_tree_reading)
{
if (settings.allow_asynchronous_read_from_io_pool_for_merge_tree)
{
/// When async reading is enabled, allow to read using more streams.
/// Will add resize to output_streams_limit to reduce memory usage.
output_streams_limit = std::min<size_t>(requested_num_streams, settings.max_streams_for_merge_tree_reading);
/// We intentionally set `max_streams` to 1 in InterpreterSelectQuery in case of small limit.
/// Changing it here to `max_streams_for_merge_tree_reading` proven itself as a threat for performance.
if (requested_num_streams != 1)
requested_num_streams = std::max<size_t>(requested_num_streams, settings.max_streams_for_merge_tree_reading);
}
else
/// Just limit requested_num_streams otherwise.
requested_num_streams = std::min<size_t>(requested_num_streams, settings.max_streams_for_merge_tree_reading);
}
/// Add explicit description.
setStepDescription(data.getStorageID().getFullNameNotQuoted());
updateSortDescriptionForOutputStream(
*output_stream,
storage_snapshot->getMetadataForQuery()->getSortingKeyColumns(),
getSortDirection(),
query_info.getInputOrderInfo(),
prewhere_info);
}
Pipe ReadFromMergeTree::readFromPoolParallelReplicas(
RangesInDataParts parts_with_range,
Names required_columns,
PoolSettings pool_settings)
{
const auto & client_info = context->getClientInfo();
auto extension = ParallelReadingExtension
{
.all_callback = all_ranges_callback.value(),
.callback = read_task_callback.value(),
.count_participating_replicas = client_info.count_participating_replicas,
.number_of_current_replica = client_info.number_of_current_replica,
.columns_to_read = required_columns,
};
/// We have a special logic for local replica. It has to read less data, because in some cases it should
/// merge states of aggregate functions or do some other important stuff other than reading from Disk.
pool_settings.min_marks_for_concurrent_read = static_cast<size_t>(pool_settings.min_marks_for_concurrent_read * context->getSettingsRef().parallel_replicas_single_task_marks_count_multiplier);
auto pool = std::make_shared<MergeTreeReadPoolParallelReplicas>(
std::move(extension),
std::move(parts_with_range),
storage_snapshot,
prewhere_info,
actions_settings,
reader_settings,
required_columns,
virt_column_names,
pool_settings,
context);
auto block_size_copy = block_size;
block_size_copy.min_marks_to_read = pool_settings.min_marks_for_concurrent_read;
Pipes pipes;
for (size_t i = 0; i < pool_settings.threads; ++i)
{
auto algorithm = std::make_unique<MergeTreeThreadSelectAlgorithm>(i);
auto processor = std::make_unique<MergeTreeSelectProcessor>(
pool, std::move(algorithm), data, prewhere_info,
actions_settings, block_size_copy, reader_settings, virt_column_names);
auto source = std::make_shared<MergeTreeSource>(std::move(processor));
pipes.emplace_back(std::move(source));
}
return Pipe::unitePipes(std::move(pipes));
}
Pipe ReadFromMergeTree::readFromPool(
RangesInDataParts parts_with_range,
Names required_columns,
PoolSettings pool_settings)
{
size_t total_rows = parts_with_range.getRowsCountAllParts();
if (query_info.limit > 0 && query_info.limit < total_rows)
total_rows = query_info.limit;
const auto & settings = context->getSettingsRef();
/// round min_marks_to_read up to nearest multiple of block_size expressed in marks
/// If granularity is adaptive it doesn't make sense
/// Maybe it will make sense to add settings `max_block_size_bytes`
if (block_size.max_block_size_rows && !data.canUseAdaptiveGranularity())
{
size_t fixed_index_granularity = data.getSettings()->index_granularity;
pool_settings.min_marks_for_concurrent_read = (pool_settings.min_marks_for_concurrent_read * fixed_index_granularity + block_size.max_block_size_rows - 1)
/ block_size.max_block_size_rows * block_size.max_block_size_rows / fixed_index_granularity;
}
bool all_parts_are_remote = true;
bool all_parts_are_local = true;
for (const auto & part : parts_with_range)
{
const bool is_remote = part.data_part->isStoredOnRemoteDisk();
all_parts_are_local &= !is_remote;
all_parts_are_remote &= is_remote;
}
MergeTreeReadPoolPtr pool;
bool allow_prefetched_remote = all_parts_are_remote
&& settings.allow_prefetched_read_pool_for_remote_filesystem
&& MergeTreePrefetchedReadPool::checkReadMethodAllowed(reader_settings.read_settings.remote_fs_method);
bool allow_prefetched_local = all_parts_are_local
&& settings.allow_prefetched_read_pool_for_local_filesystem
&& MergeTreePrefetchedReadPool::checkReadMethodAllowed(reader_settings.read_settings.local_fs_method);
if (allow_prefetched_remote || allow_prefetched_local)
{
pool = std::make_shared<MergeTreePrefetchedReadPool>(
std::move(parts_with_range),
storage_snapshot,
prewhere_info,
actions_settings,
reader_settings,
required_columns,
virt_column_names,
pool_settings,
context);
}
else
{
pool = std::make_shared<MergeTreeReadPool>(
std::move(parts_with_range),
storage_snapshot,
prewhere_info,
actions_settings,
reader_settings,
required_columns,
virt_column_names,
pool_settings,
context);
}
LOG_DEBUG(log, "Reading approx. {} rows with {} streams", total_rows, pool_settings.threads);
/// The reason why we change this setting is because MergeTreeReadPool takes the full task
/// ignoring min_marks_to_read setting in case of remote disk (see MergeTreeReadPool::getTask).
/// In this case, we won't limit the number of rows to read based on adaptive granularity settings.
auto block_size_copy = block_size;
block_size_copy.min_marks_to_read = pool_settings.min_marks_for_concurrent_read;
Pipes pipes;
for (size_t i = 0; i < pool_settings.threads; ++i)
{
auto algorithm = std::make_unique<MergeTreeThreadSelectAlgorithm>(i);
auto processor = std::make_unique<MergeTreeSelectProcessor>(
pool, std::move(algorithm), data, prewhere_info,
actions_settings, block_size_copy, reader_settings, virt_column_names);
auto source = std::make_shared<MergeTreeSource>(std::move(processor));
if (i == 0)
source->addTotalRowsApprox(total_rows);
pipes.emplace_back(std::move(source));
}
auto pipe = Pipe::unitePipes(std::move(pipes));
if (output_streams_limit && output_streams_limit < pipe.numOutputPorts())
pipe.resize(output_streams_limit);
return pipe;
}
Pipe ReadFromMergeTree::readInOrder(
RangesInDataParts parts_with_ranges,
Names required_columns,
PoolSettings pool_settings,
ReadType read_type,
UInt64 limit)
{
/// For reading in order it makes sense to read only
/// one range per task to reduce number of read rows.
bool has_limit_below_one_block = read_type != ReadType::Default && limit && limit < block_size.max_block_size_rows;
MergeTreeReadPoolPtr pool;
if (is_parallel_reading_from_replicas)
{
const auto & client_info = context->getClientInfo();
ParallelReadingExtension extension
{
.all_callback = all_ranges_callback.value(),
.callback = read_task_callback.value(),
.count_participating_replicas = client_info.count_participating_replicas,
.number_of_current_replica = client_info.number_of_current_replica,
.columns_to_read = required_columns,
};
pool_settings.min_marks_for_concurrent_read = static_cast<size_t>(
pool_settings.min_marks_for_concurrent_read * context->getSettingsRef().parallel_replicas_single_task_marks_count_multiplier);
CoordinationMode mode = read_type == ReadType::InOrder
? CoordinationMode::WithOrder
: CoordinationMode::ReverseOrder;
pool = std::make_shared<MergeTreeReadPoolParallelReplicasInOrder>(
std::move(extension),
mode,
parts_with_ranges,
storage_snapshot,
prewhere_info,
actions_settings,
reader_settings,
required_columns,
virt_column_names,
pool_settings,
context);
}
else
{
pool = std::make_shared<MergeTreeReadPoolInOrder>(
has_limit_below_one_block,
read_type,
parts_with_ranges,
storage_snapshot,
prewhere_info,
actions_settings,
reader_settings,
required_columns,
virt_column_names,
pool_settings,
context);
}
/// Actually it means that parallel reading from replicas enabled
/// and we have to collaborate with initiator.
/// In this case we won't set approximate rows, because it will be accounted multiple times.
/// Also do not count amount of read rows if we read in order of sorting key,
/// because we don't know actual amount of read rows in case when limit is set.
bool set_rows_approx = !is_parallel_reading_from_replicas && !reader_settings.read_in_order;
Pipes pipes;
for (size_t i = 0; i < parts_with_ranges.size(); ++i)
{
const auto & part_with_ranges = parts_with_ranges[i];
UInt64 total_rows = part_with_ranges.getRowsCount();
if (query_info.limit > 0 && query_info.limit < total_rows)
total_rows = query_info.limit;
LOG_TRACE(log, "Reading {} ranges in{}order from part {}, approx. {} rows starting from {}",
part_with_ranges.ranges.size(),
read_type == ReadType::InReverseOrder ? " reverse " : " ",
part_with_ranges.data_part->name, total_rows,
part_with_ranges.data_part->index_granularity.getMarkStartingRow(part_with_ranges.ranges.front().begin));
MergeTreeSelectAlgorithmPtr algorithm;
if (read_type == ReadType::InReverseOrder)
algorithm = std::make_unique<MergeTreeInReverseOrderSelectAlgorithm>(i);
else
algorithm = std::make_unique<MergeTreeInOrderSelectAlgorithm>(i);
auto processor = std::make_unique<MergeTreeSelectProcessor>(
pool, std::move(algorithm), data, prewhere_info,
actions_settings, block_size, reader_settings, virt_column_names);
auto source = std::make_shared<MergeTreeSource>(std::move(processor));
if (set_rows_approx)
source->addTotalRowsApprox(total_rows);
pipes.emplace_back(std::move(source));
}
auto pipe = Pipe::unitePipes(std::move(pipes));
if (read_type == ReadType::InReverseOrder)
{
pipe.addSimpleTransform([&](const Block & header)
{
return std::make_shared<ReverseTransform>(header);
});
}
return pipe;
}
Pipe ReadFromMergeTree::read(
RangesInDataParts parts_with_range,
Names required_columns,
ReadType read_type,
size_t max_streams,
size_t min_marks_for_concurrent_read,
bool use_uncompressed_cache)
{
const auto & settings = context->getSettingsRef();
size_t sum_marks = parts_with_range.getMarksCountAllParts();
PoolSettings pool_settings
{
.threads = max_streams,
.sum_marks = sum_marks,
.min_marks_for_concurrent_read = min_marks_for_concurrent_read,
.preferred_block_size_bytes = settings.preferred_block_size_bytes,
.use_uncompressed_cache = use_uncompressed_cache,
.use_const_size_tasks_for_remote_reading = settings.merge_tree_use_const_size_tasks_for_remote_reading,
};
if (read_type == ReadType::ParallelReplicas)
return readFromPoolParallelReplicas(std::move(parts_with_range), std::move(required_columns), std::move(pool_settings));
/// Reading from default thread pool is beneficial for remote storage because of new prefetches.
if (read_type == ReadType::Default && (max_streams > 1 || checkAllPartsOnRemoteFS(parts_with_range)))
return readFromPool(std::move(parts_with_range), std::move(required_columns), std::move(pool_settings));
auto pipe = readInOrder(parts_with_range, required_columns, pool_settings, read_type, /*limit=*/ 0);
/// Use ConcatProcessor to concat sources together.
/// It is needed to read in parts order (and so in PK order) if single thread is used.
if (read_type == ReadType::Default && pipe.numOutputPorts() > 1)
pipe.addTransform(std::make_shared<ConcatProcessor>(pipe.getHeader(), pipe.numOutputPorts()));
return pipe;
}
namespace
{
struct PartRangesReadInfo
{
std::vector<size_t> sum_marks_in_parts;
size_t sum_marks = 0;
size_t total_rows = 0;
size_t adaptive_parts = 0;
size_t index_granularity_bytes = 0;
size_t max_marks_to_use_cache = 0;
size_t min_marks_for_concurrent_read = 0;
bool use_uncompressed_cache = false;
PartRangesReadInfo(
const RangesInDataParts & parts,
const Settings & settings,
const MergeTreeSettings & data_settings)
{
/// Count marks for each part.
sum_marks_in_parts.resize(parts.size());
for (size_t i = 0; i < parts.size(); ++i)
{
total_rows += parts[i].getRowsCount();
sum_marks_in_parts[i] = parts[i].getMarksCount();
sum_marks += sum_marks_in_parts[i];
if (parts[i].data_part->index_granularity_info.mark_type.adaptive)
++adaptive_parts;
}
if (adaptive_parts > parts.size() / 2)
index_granularity_bytes = data_settings.index_granularity_bytes;
max_marks_to_use_cache = MergeTreeDataSelectExecutor::roundRowsOrBytesToMarks(
settings.merge_tree_max_rows_to_use_cache,
settings.merge_tree_max_bytes_to_use_cache,
data_settings.index_granularity,
index_granularity_bytes);
auto all_parts_on_remote_disk = checkAllPartsOnRemoteFS(parts);
size_t min_rows_for_concurrent_read;
size_t min_bytes_for_concurrent_read;
if (all_parts_on_remote_disk)
{
min_rows_for_concurrent_read = settings.merge_tree_min_rows_for_concurrent_read_for_remote_filesystem;
min_bytes_for_concurrent_read = settings.merge_tree_min_bytes_for_concurrent_read_for_remote_filesystem;
}
else
{
min_rows_for_concurrent_read = settings.merge_tree_min_rows_for_concurrent_read;
min_bytes_for_concurrent_read = settings.merge_tree_min_bytes_for_concurrent_read;
}
min_marks_for_concurrent_read = MergeTreeDataSelectExecutor::minMarksForConcurrentRead(
min_rows_for_concurrent_read, min_bytes_for_concurrent_read,
data_settings.index_granularity, index_granularity_bytes, sum_marks);
use_uncompressed_cache = settings.use_uncompressed_cache;
if (sum_marks > max_marks_to_use_cache)
use_uncompressed_cache = false;
}
};
}
Pipe ReadFromMergeTree::spreadMarkRangesAmongStreams(RangesInDataParts && parts_with_ranges, size_t num_streams, const Names & column_names)
{
const auto & settings = context->getSettingsRef();
const auto data_settings = data.getSettings();
LOG_TRACE(log, "Spreading mark ranges among streams (default reading)");
PartRangesReadInfo info(parts_with_ranges, settings, *data_settings);
if (0 == info.sum_marks)
return {};
if (num_streams > 1)
{
/// Reduce the number of num_streams if the data is small.
if (info.sum_marks < num_streams * info.min_marks_for_concurrent_read && parts_with_ranges.size() < num_streams)
{
/*
If the data is fragmented, then allocate the size of parts to num_streams. If the data is not fragmented, besides the sum_marks and
min_marks_for_concurrent_read, involve the system cores to get the num_streams. Increase the num_streams and decrease the min_marks_for_concurrent_read
if the data is small but system has plentiful cores. It helps to improve the parallel performance of `MergeTreeRead` significantly.
Make sure the new num_streams `num_streams * increase_num_streams_ratio` will not exceed the previous calculated prev_num_streams.
The new info.min_marks_for_concurrent_read `info.min_marks_for_concurrent_read / increase_num_streams_ratio` should be larger than 8.
https://github.com/ClickHouse/ClickHouse/pull/53867
*/
if ((info.sum_marks + info.min_marks_for_concurrent_read - 1) / info.min_marks_for_concurrent_read > parts_with_ranges.size())
{
const size_t prev_num_streams = num_streams;
num_streams = (info.sum_marks + info.min_marks_for_concurrent_read - 1) / info.min_marks_for_concurrent_read;
const size_t increase_num_streams_ratio = std::min(prev_num_streams / num_streams, info.min_marks_for_concurrent_read / 8);
if (increase_num_streams_ratio > 1)
{
num_streams = num_streams * increase_num_streams_ratio;
info.min_marks_for_concurrent_read = (info.sum_marks + num_streams - 1) / num_streams;
}
}
else
num_streams = parts_with_ranges.size();
}
}
auto read_type = is_parallel_reading_from_replicas ? ReadType::ParallelReplicas : ReadType::Default;
return read(std::move(parts_with_ranges),
column_names,
read_type,
num_streams,
info.min_marks_for_concurrent_read,
info.use_uncompressed_cache);
}
static ActionsDAGPtr createProjection(const Block & header)
{
auto projection = std::make_shared<ActionsDAG>(header.getNamesAndTypesList());
projection->removeUnusedActions(header.getNames());
projection->projectInput();
return projection;
}
Pipe ReadFromMergeTree::spreadMarkRangesAmongStreamsWithOrder(
RangesInDataParts && parts_with_ranges,
size_t num_streams,
const Names & column_names,
ActionsDAGPtr & out_projection,
const InputOrderInfoPtr & input_order_info)
{
const auto & settings = context->getSettingsRef();
const auto data_settings = data.getSettings();
LOG_TRACE(log, "Spreading ranges among streams with order");
PartRangesReadInfo info(parts_with_ranges, settings, *data_settings);
Pipes res;
if (info.sum_marks == 0)
return {};
/// PREWHERE actions can remove some input columns (which are needed only for prewhere condition).
/// In case of read-in-order, PREWHERE is executed before sorting. But removed columns could be needed for sorting key.
/// To fix this, we prohibit removing any input in prewhere actions. Instead, projection actions will be added after sorting.
/// See 02354_read_in_order_prewhere.sql as an example.
bool have_input_columns_removed_after_prewhere = false;
if (prewhere_info && prewhere_info->prewhere_actions)
{
auto & outputs = prewhere_info->prewhere_actions->getOutputs();
std::unordered_set<const ActionsDAG::Node *> outputs_set(outputs.begin(), outputs.end());
for (const auto * input : prewhere_info->prewhere_actions->getInputs())
{
if (!outputs_set.contains(input))
{
outputs.push_back(input);
have_input_columns_removed_after_prewhere = true;
}
}
}
/// Let's split ranges to avoid reading much data.
auto split_ranges
= [rows_granularity = data_settings->index_granularity, my_max_block_size = block_size.max_block_size_rows]
(const auto & ranges, int direction)
{
MarkRanges new_ranges;
const size_t max_marks_in_range = (my_max_block_size + rows_granularity - 1) / rows_granularity;
size_t marks_in_range = 1;
if (direction == 1)
{
/// Split first few ranges to avoid reading much data.
bool split = false;
for (auto range : ranges)
{
while (!split && range.begin + marks_in_range < range.end)
{
new_ranges.emplace_back(range.begin, range.begin + marks_in_range);
range.begin += marks_in_range;
marks_in_range *= 2;
if (marks_in_range > max_marks_in_range)
split = true;
}
new_ranges.emplace_back(range.begin, range.end);
}
}
else
{
/// Split all ranges to avoid reading much data, because we have to
/// store whole range in memory to reverse it.
for (auto it = ranges.rbegin(); it != ranges.rend(); ++it)
{
auto range = *it;
while (range.begin + marks_in_range < range.end)
{
new_ranges.emplace_front(range.end - marks_in_range, range.end);
range.end -= marks_in_range;
marks_in_range = std::min(marks_in_range * 2, max_marks_in_range);
}
new_ranges.emplace_front(range.begin, range.end);
}
}
return new_ranges;
};
const size_t min_marks_per_stream = (info.sum_marks - 1) / num_streams + 1;
bool need_preliminary_merge = (parts_with_ranges.size() > settings.read_in_order_two_level_merge_threshold);
const auto read_type = input_order_info->direction == 1 ? ReadType::InOrder : ReadType::InReverseOrder;
PoolSettings pool_settings
{
.min_marks_for_concurrent_read = info.min_marks_for_concurrent_read,
.preferred_block_size_bytes = settings.preferred_block_size_bytes,
.use_uncompressed_cache = info.use_uncompressed_cache,
};
Pipes pipes;
/// For parallel replicas the split will be performed on the initiator side.
if (is_parallel_reading_from_replicas)
{
pipes.emplace_back(readInOrder(std::move(parts_with_ranges), column_names, pool_settings, read_type, input_order_info->limit));
}
else
{
std::vector<RangesInDataParts> splitted_parts_and_ranges;
splitted_parts_and_ranges.reserve(num_streams);
for (size_t i = 0; i < num_streams && !parts_with_ranges.empty(); ++i)
{
size_t need_marks = min_marks_per_stream;
RangesInDataParts new_parts;
/// Loop over parts.
/// We will iteratively take part or some subrange of a part from the back
/// and assign a stream to read from it.
while (need_marks > 0 && !parts_with_ranges.empty())
{
RangesInDataPart part = parts_with_ranges.back();
parts_with_ranges.pop_back();
size_t & marks_in_part = info.sum_marks_in_parts.back();
/// We will not take too few rows from a part.
if (marks_in_part >= info.min_marks_for_concurrent_read && need_marks < info.min_marks_for_concurrent_read)
need_marks = info.min_marks_for_concurrent_read;
/// Do not leave too few rows in the part.
if (marks_in_part > need_marks && marks_in_part - need_marks < info.min_marks_for_concurrent_read)
need_marks = marks_in_part;
MarkRanges ranges_to_get_from_part;
/// We take full part if it contains enough marks or
/// if we know limit and part contains less than 'limit' rows.
bool take_full_part = marks_in_part <= need_marks || (input_order_info->limit && input_order_info->limit < part.getRowsCount());
/// We take the whole part if it is small enough.
if (take_full_part)
{
ranges_to_get_from_part = part.ranges;
need_marks -= marks_in_part;
info.sum_marks_in_parts.pop_back();
}
else
{
/// Loop through ranges in part. Take enough ranges to cover "need_marks".
while (need_marks > 0)
{
if (part.ranges.empty())
throw Exception(ErrorCodes::LOGICAL_ERROR, "Unexpected end of ranges while spreading marks among streams");
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();
}
parts_with_ranges.emplace_back(part);
}
ranges_to_get_from_part = split_ranges(ranges_to_get_from_part, input_order_info->direction);
new_parts.emplace_back(part.data_part, part.alter_conversions, part.part_index_in_query, std::move(ranges_to_get_from_part));
}
splitted_parts_and_ranges.emplace_back(std::move(new_parts));
}
for (auto && item : splitted_parts_and_ranges)
pipes.emplace_back(readInOrder(std::move(item), column_names, pool_settings, read_type, input_order_info->limit));
}
Block pipe_header;
if (!pipes.empty())
pipe_header = pipes.front().getHeader();
if (need_preliminary_merge || output_each_partition_through_separate_port)
{
size_t prefix_size = input_order_info->used_prefix_of_sorting_key_size;
auto order_key_prefix_ast = metadata_for_reading->getSortingKey().expression_list_ast->clone();
order_key_prefix_ast->children.resize(prefix_size);
auto syntax_result = TreeRewriter(context).analyze(order_key_prefix_ast, metadata_for_reading->getColumns().getAllPhysical());
auto sorting_key_prefix_expr = ExpressionAnalyzer(order_key_prefix_ast, syntax_result, context).getActionsDAG(false);
const auto & sorting_columns = metadata_for_reading->getSortingKey().column_names;
SortDescription sort_description;
sort_description.compile_sort_description = settings.compile_sort_description;
sort_description.min_count_to_compile_sort_description = settings.min_count_to_compile_sort_description;
for (size_t j = 0; j < prefix_size; ++j)
sort_description.emplace_back(sorting_columns[j], input_order_info->direction);
auto sorting_key_expr = std::make_shared<ExpressionActions>(sorting_key_prefix_expr);
auto merge_streams = [&](Pipe & pipe)
{
pipe.addSimpleTransform([sorting_key_expr](const Block & header)
{ return std::make_shared<ExpressionTransform>(header, sorting_key_expr); });
if (pipe.numOutputPorts() > 1)
{
auto transform = std::make_shared<MergingSortedTransform>(
pipe.getHeader(), pipe.numOutputPorts(), sort_description, block_size.max_block_size_rows, /*max_block_size_bytes=*/0, SortingQueueStrategy::Batch);
pipe.addTransform(std::move(transform));
}
};
if (!pipes.empty() && output_each_partition_through_separate_port)
{
/// In contrast with usual aggregation in order that allocates separate AggregatingTransform for each data part,
/// aggregation of partitioned data uses the same AggregatingTransform for all parts of the same partition.
/// Thus we need to merge all partition parts into a single sorted stream.
Pipe pipe = Pipe::unitePipes(std::move(pipes));
merge_streams(pipe);
out_projection = createProjection(pipe_header);
return pipe;
}
for (auto & pipe : pipes)
merge_streams(pipe);
}
if (!pipes.empty() && (need_preliminary_merge || have_input_columns_removed_after_prewhere))
/// Drop temporary columns, added by 'sorting_key_prefix_expr'
out_projection = createProjection(pipe_header);
return Pipe::unitePipes(std::move(pipes));
}
static void addMergingFinal(
Pipe & pipe,
const SortDescription & sort_description,
MergeTreeData::MergingParams merging_params,
Names partition_key_columns,
size_t max_block_size_rows)
{