ClickHouse/src/Storages/MergeTree/MergeTreeReverseSelectProcessor.cpp
2021-05-11 18:12:27 +08:00

158 lines
5.2 KiB
C++

#include <Storages/MergeTree/MergeTreeReverseSelectProcessor.h>
#include <Storages/MergeTree/MergeTreeBaseSelectProcessor.h>
#include <Storages/MergeTree/IMergeTreeReader.h>
#include <Interpreters/Context.h>
namespace DB
{
namespace ErrorCodes
{
extern const int MEMORY_LIMIT_EXCEEDED;
}
MergeTreeReverseSelectProcessor::MergeTreeReverseSelectProcessor(
const MergeTreeData & storage_,
const StorageMetadataPtr & metadata_snapshot_,
const MergeTreeData::DataPartPtr & owned_data_part_,
UInt64 max_block_size_rows_,
size_t preferred_block_size_bytes_,
size_t preferred_max_column_in_block_size_bytes_,
Names required_columns_,
MarkRanges mark_ranges_,
bool use_uncompressed_cache_,
const PrewhereInfoPtr & prewhere_info_,
bool check_columns,
const MergeTreeReaderSettings & reader_settings_,
const Names & virt_column_names_,
size_t part_index_in_query_,
bool quiet)
:
MergeTreeBaseSelectProcessor{
metadata_snapshot_->getSampleBlockForColumns(required_columns_, storage_.getVirtuals(), storage_.getStorageID()),
storage_, metadata_snapshot_, prewhere_info_, max_block_size_rows_,
preferred_block_size_bytes_, preferred_max_column_in_block_size_bytes_,
reader_settings_, use_uncompressed_cache_, virt_column_names_},
required_columns{std::move(required_columns_)},
data_part{owned_data_part_},
all_mark_ranges(std::move(mark_ranges_)),
part_index_in_query(part_index_in_query_),
path(data_part->getFullRelativePath())
{
/// Let's estimate total number of rows for progress bar.
for (const auto & range : all_mark_ranges)
total_marks_count += range.end - range.begin;
size_t total_rows = data_part->index_granularity.getRowsCountInRanges(all_mark_ranges);
if (!quiet)
LOG_DEBUG(log, "Reading {} ranges in reverse order from part {}, approx. {} rows starting from {}",
all_mark_ranges.size(), data_part->name, total_rows,
data_part->index_granularity.getMarkStartingRow(all_mark_ranges.front().begin));
addTotalRowsApprox(total_rows);
ordered_names = header_without_virtual_columns.getNames();
task_columns = getReadTaskColumns(storage, metadata_snapshot, data_part, required_columns, prewhere_info, check_columns);
/// will be used to distinguish between PREWHERE and WHERE columns when applying filter
const auto & column_names = task_columns.columns.getNames();
column_name_set = NameSet{column_names.begin(), column_names.end()};
if (use_uncompressed_cache)
owned_uncompressed_cache = storage.getContext()->getUncompressedCache();
owned_mark_cache = storage.getContext()->getMarkCache();
reader = data_part->getReader(task_columns.columns, metadata_snapshot,
all_mark_ranges, owned_uncompressed_cache.get(),
owned_mark_cache.get(), reader_settings);
if (prewhere_info)
pre_reader = data_part->getReader(task_columns.pre_columns, metadata_snapshot, all_mark_ranges,
owned_uncompressed_cache.get(), owned_mark_cache.get(), reader_settings);
}
bool MergeTreeReverseSelectProcessor::getNewTask()
try
{
if ((chunks.empty() && all_mark_ranges.empty()) || total_marks_count == 0)
{
finish();
return false;
}
/// We have some blocks to return in buffer.
/// Return true to continue reading, but actually don't create a task.
if (all_mark_ranges.empty())
return true;
/// Read ranges from right to left.
MarkRanges mark_ranges_for_task = { all_mark_ranges.back() };
all_mark_ranges.pop_back();
auto size_predictor = (preferred_block_size_bytes == 0)
? nullptr
: std::make_unique<MergeTreeBlockSizePredictor>(data_part, ordered_names, metadata_snapshot->getSampleBlock());
task = std::make_unique<MergeTreeReadTask>(
data_part, mark_ranges_for_task, part_index_in_query, ordered_names, column_name_set,
task_columns.columns, task_columns.pre_columns, prewhere_info && prewhere_info->remove_prewhere_column,
task_columns.should_reorder, std::move(size_predictor));
return true;
}
catch (...)
{
/// Suspicion of the broken part. A part is added to the queue for verification.
if (getCurrentExceptionCode() != ErrorCodes::MEMORY_LIMIT_EXCEEDED)
storage.reportBrokenPart(data_part->name);
throw;
}
Chunk MergeTreeReverseSelectProcessor::readFromPart()
{
Chunk res;
if (!chunks.empty())
{
res = std::move(chunks.back());
chunks.pop_back();
return res;
}
if (!task->range_reader.isInitialized())
initializeRangeReaders(*task);
while (!task->isFinished())
{
Chunk chunk = readFromPartImpl();
chunks.push_back(std::move(chunk));
}
if (chunks.empty())
return {};
res = std::move(chunks.back());
chunks.pop_back();
return res;
}
void MergeTreeReverseSelectProcessor::finish()
{
/** Close the files (before destroying the object).
* When many sources are created, but simultaneously reading only a few of them,
* buffers don't waste memory.
*/
reader.reset();
pre_reader.reset();
data_part.reset();
}
MergeTreeReverseSelectProcessor::~MergeTreeReverseSelectProcessor() = default;
}