ClickHouse/dbms/Storages/MergeTree/MergeTreeBaseSelectProcessor.cpp

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#include <Storages/MergeTree/MergeTreeBaseSelectProcessor.h>
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#include <Storages/MergeTree/MergeTreeRangeReader.h>
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#include <Storages/MergeTree/IMergeTreeDataPart.h>
#include <Storages/MergeTree/IMergeTreeReader.h>
#include <Storages/MergeTree/MergeTreeBlockReadUtils.h>
#include <Columns/FilterDescription.h>
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#include <Common/typeid_cast.h>
#include <DataTypes/DataTypeNothing.h>
namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
}
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MergeTreeBaseSelectProcessor::MergeTreeBaseSelectProcessor(
Block header,
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const MergeTreeData & storage_,
const PrewhereInfoPtr & prewhere_info_,
UInt64 max_block_size_rows_,
UInt64 preferred_block_size_bytes_,
UInt64 preferred_max_column_in_block_size_bytes_,
const MergeTreeReaderSettings & reader_settings_,
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bool use_uncompressed_cache_,
const Names & virt_column_names_)
:
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SourceWithProgress(getHeader(std::move(header), prewhere_info_, virt_column_names_)),
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storage(storage_),
prewhere_info(prewhere_info_),
max_block_size_rows(max_block_size_rows_),
preferred_block_size_bytes(preferred_block_size_bytes_),
preferred_max_column_in_block_size_bytes(preferred_max_column_in_block_size_bytes_),
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reader_settings(reader_settings_),
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use_uncompressed_cache(use_uncompressed_cache_),
virt_column_names(virt_column_names_)
{
header_without_virtual_columns = getPort().getHeader();
for (auto it = virt_column_names.rbegin(); it != virt_column_names.rend(); ++it)
if (header_without_virtual_columns.has(*it))
header_without_virtual_columns.erase(*it);
}
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Chunk MergeTreeBaseSelectProcessor::generate()
{
while (!isCancelled())
{
if ((!task || task->isFinished()) && !getNewTask())
return {};
auto res = readFromPart();
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if (res.hasRows())
{
injectVirtualColumns(res, task.get(), virt_column_names);
return res;
}
}
return {};
}
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void MergeTreeBaseSelectProcessor::initializeRangeReaders(MergeTreeReadTask & current_task)
{
if (prewhere_info)
{
if (reader->getColumns().empty())
{
current_task.range_reader = MergeTreeRangeReader(pre_reader.get(), nullptr, prewhere_info, true);
}
else
{
MergeTreeRangeReader * pre_reader_ptr = nullptr;
if (pre_reader != nullptr)
{
current_task.pre_range_reader = MergeTreeRangeReader(pre_reader.get(), nullptr, prewhere_info, false);
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pre_reader_ptr = &current_task.pre_range_reader;
}
current_task.range_reader = MergeTreeRangeReader(reader.get(), pre_reader_ptr, nullptr, true);
}
}
else
{
current_task.range_reader = MergeTreeRangeReader(reader.get(), nullptr, nullptr, true);
}
}
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Chunk MergeTreeBaseSelectProcessor::readFromPartImpl()
{
if (task->size_predictor)
task->size_predictor->startBlock();
const UInt64 current_max_block_size_rows = max_block_size_rows;
const UInt64 current_preferred_block_size_bytes = preferred_block_size_bytes;
const UInt64 current_preferred_max_column_in_block_size_bytes = preferred_max_column_in_block_size_bytes;
const MergeTreeIndexGranularity & index_granularity = task->data_part->index_granularity;
const double min_filtration_ratio = 0.00001;
auto estimate_num_rows = [current_preferred_block_size_bytes, current_max_block_size_rows,
&index_granularity, current_preferred_max_column_in_block_size_bytes, min_filtration_ratio](
MergeTreeReadTask & current_task, MergeTreeRangeReader & current_reader)
{
if (!current_task.size_predictor)
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return static_cast<size_t>(current_max_block_size_rows);
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/// Calculates number of rows will be read using preferred_block_size_bytes.
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/// Can't be less than avg_index_granularity.
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size_t rows_to_read = current_task.size_predictor->estimateNumRows(current_preferred_block_size_bytes);
if (!rows_to_read)
return rows_to_read;
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auto total_row_in_current_granule = current_reader.numRowsInCurrentGranule();
rows_to_read = std::max(total_row_in_current_granule, rows_to_read);
if (current_preferred_max_column_in_block_size_bytes)
{
/// Calculates number of rows will be read using preferred_max_column_in_block_size_bytes.
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auto rows_to_read_for_max_size_column
= current_task.size_predictor->estimateNumRowsForMaxSizeColumn(current_preferred_max_column_in_block_size_bytes);
double filtration_ratio = std::max(min_filtration_ratio, 1.0 - current_task.size_predictor->filtered_rows_ratio);
auto rows_to_read_for_max_size_column_with_filtration
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= static_cast<size_t>(rows_to_read_for_max_size_column / filtration_ratio);
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/// If preferred_max_column_in_block_size_bytes is used, number of rows to read can be less than current_index_granularity.
rows_to_read = std::min(rows_to_read, rows_to_read_for_max_size_column_with_filtration);
}
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auto unread_rows_in_current_granule = current_reader.numPendingRowsInCurrentGranule();
if (unread_rows_in_current_granule >= rows_to_read)
return rows_to_read;
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return index_granularity.countMarksForRows(current_reader.currentMark(), rows_to_read, current_reader.numReadRowsInCurrentGranule());
};
UInt64 recommended_rows = estimate_num_rows(*task, task->range_reader);
UInt64 rows_to_read = std::max(UInt64(1), std::min(current_max_block_size_rows, recommended_rows));
auto read_result = task->range_reader.read(rows_to_read, task->mark_ranges);
/// All rows were filtered. Repeat.
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if (read_result.num_rows == 0)
read_result.columns.clear();
auto & sample_block = task->range_reader.getSampleBlock();
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if (read_result.num_rows != 0 && sample_block.columns() != read_result.columns.size())
throw Exception("Inconsistent number of columns got from MergeTreeRangeReader. "
"Have " + toString(sample_block.columns()) + " in sample block "
"and " + toString(read_result.columns.size()) + " columns in list", ErrorCodes::LOGICAL_ERROR);
/// TODO: check columns have the same types as in header.
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UInt64 num_filtered_rows = read_result.numReadRows() - read_result.num_rows;
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progress({ read_result.numReadRows(), read_result.numBytesRead() });
if (task->size_predictor)
{
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task->size_predictor->updateFilteredRowsRation(read_result.numReadRows(), num_filtered_rows);
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if (!read_result.columns.empty())
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task->size_predictor->update(sample_block, read_result.columns, read_result.num_rows);
}
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if (read_result.num_rows == 0)
return {};
Columns ordered_columns;
ordered_columns.reserve(header_without_virtual_columns.columns());
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/// Reorder columns. TODO: maybe skip for default case.
for (size_t ps = 0; ps < header_without_virtual_columns.columns(); ++ps)
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{
auto pos_in_sample_block = sample_block.getPositionByName(header_without_virtual_columns.getByPosition(ps).name);
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ordered_columns.emplace_back(std::move(read_result.columns[pos_in_sample_block]));
}
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return Chunk(std::move(ordered_columns), read_result.num_rows);
}
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Chunk MergeTreeBaseSelectProcessor::readFromPart()
{
if (!task->range_reader.isInitialized())
initializeRangeReaders(*task);
return readFromPartImpl();
}
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namespace
{
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/// Simple interfaces to insert virtual columns.
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struct VirtualColumnsInserter
{
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virtual ~VirtualColumnsInserter() = default;
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virtual void insertStringColumn(const ColumnPtr & column, const String & name) = 0;
virtual void insertUInt64Column(const ColumnPtr & column, const String & name) = 0;
};
}
static void injectVirtualColumnsImpl(size_t rows, VirtualColumnsInserter & inserter,
MergeTreeReadTask * task, const Names & virtual_columns)
{
/// add virtual columns
/// Except _sample_factor, which is added from the outside.
if (!virtual_columns.empty())
{
if (unlikely(rows && !task))
throw Exception("Cannot insert virtual columns to non-empty chunk without specified task.",
ErrorCodes::LOGICAL_ERROR);
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for (const auto & virtual_column_name : virtual_columns)
{
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if (virtual_column_name == "_part")
{
ColumnPtr column;
if (rows)
column = DataTypeString().createColumnConst(rows, task->data_part->name)->convertToFullColumnIfConst();
else
column = DataTypeString().createColumn();
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inserter.insertStringColumn(column, virtual_column_name);
}
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else if (virtual_column_name == "_part_index")
{
ColumnPtr column;
if (rows)
column = DataTypeUInt64().createColumnConst(rows, task->part_index_in_query)->convertToFullColumnIfConst();
else
column = DataTypeUInt64().createColumn();
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inserter.insertUInt64Column(column, virtual_column_name);
}
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else if (virtual_column_name == "_partition_id")
{
ColumnPtr column;
if (rows)
column = DataTypeString().createColumnConst(rows, task->data_part->info.partition_id)->convertToFullColumnIfConst();
else
column = DataTypeString().createColumn();
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inserter.insertStringColumn(column, virtual_column_name);
}
}
}
}
namespace
{
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struct VirtualColumnsInserterIntoBlock : public VirtualColumnsInserter
{
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explicit VirtualColumnsInserterIntoBlock(Block & block_) : block(block_) {}
void insertStringColumn(const ColumnPtr & column, const String & name) final
{
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block.insert({column, std::make_shared<DataTypeString>(), name});
}
void insertUInt64Column(const ColumnPtr & column, const String & name) final
{
block.insert({column, std::make_shared<DataTypeUInt64>(), name});
}
Block & block;
};
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struct VirtualColumnsInserterIntoColumns : public VirtualColumnsInserter
{
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explicit VirtualColumnsInserterIntoColumns(Columns & columns_) : columns(columns_) {}
void insertStringColumn(const ColumnPtr & column, const String &) final
{
columns.push_back(column);
}
void insertUInt64Column(const ColumnPtr & column, const String &) final
{
columns.push_back(column);
}
Columns & columns;
};
}
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void MergeTreeBaseSelectProcessor::injectVirtualColumns(Block & block, MergeTreeReadTask * task, const Names & virtual_columns)
{
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VirtualColumnsInserterIntoBlock inserter { block };
injectVirtualColumnsImpl(block.rows(), inserter, task, virtual_columns);
}
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void MergeTreeBaseSelectProcessor::injectVirtualColumns(Chunk & chunk, MergeTreeReadTask * task, const Names & virtual_columns)
{
UInt64 num_rows = chunk.getNumRows();
auto columns = chunk.detachColumns();
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VirtualColumnsInserterIntoColumns inserter { columns };
injectVirtualColumnsImpl(num_rows, inserter, task, virtual_columns);
chunk.setColumns(columns, num_rows);
}
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void MergeTreeBaseSelectProcessor::executePrewhereActions(Block & block, const PrewhereInfoPtr & prewhere_info)
{
if (prewhere_info)
{
if (prewhere_info->alias_actions)
prewhere_info->alias_actions->execute(block);
prewhere_info->prewhere_actions->execute(block);
if (prewhere_info->remove_prewhere_column)
block.erase(prewhere_info->prewhere_column_name);
else
{
auto & ctn = block.getByName(prewhere_info->prewhere_column_name);
ctn.type = std::make_shared<DataTypeUInt8>();
ctn.column = ctn.type->createColumnConst(block.rows(), 1u)->convertToFullColumnIfConst();
}
if (!block)
block.insert({nullptr, std::make_shared<DataTypeNothing>(), "_nothing"});
}
}
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Block MergeTreeBaseSelectProcessor::getHeader(
Block block, const PrewhereInfoPtr & prewhere_info, const Names & virtual_columns)
{
executePrewhereActions(block, prewhere_info);
injectVirtualColumns(block, nullptr, virtual_columns);
return block;
}
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MergeTreeBaseSelectProcessor::~MergeTreeBaseSelectProcessor() = default;
}