ClickHouse/dbms/include/DB/Storages/MergeTree/MergeTreeBlockInputStream.h
Andrey Mironov 9716ef7b34 Merge
2015-09-16 18:27:30 +03:00

411 lines
15 KiB
C++
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

#pragma once
#include <DB/DataStreams/IProfilingBlockInputStream.h>
#include <DB/Storages/MergeTree/MergeTreeData.h>
#include <DB/Storages/MergeTree/PKCondition.h>
#include <DB/Storages/MergeTree/MergeTreeReader.h>
namespace DB
{
/// Для чтения из одного куска. Для чтения сразу из многих, Storage использует сразу много таких объектов.
class MergeTreeBlockInputStream : public IProfilingBlockInputStream
{
public:
MergeTreeBlockInputStream(const String & path_, /// Путь к куску
size_t block_size_, Names column_names,
MergeTreeData & storage_, const MergeTreeData::DataPartPtr & owned_data_part_,
const MarkRanges & mark_ranges_, bool use_uncompressed_cache_,
ExpressionActionsPtr prewhere_actions_, String prewhere_column_, bool check_columns,
size_t min_bytes_to_use_direct_io_, size_t max_read_buffer_size_)
:
path(path_), block_size(block_size_),
storage(storage_), owned_data_part(owned_data_part_),
part_columns_lock(new Poco::ScopedReadRWLock(owned_data_part->columns_lock)),
all_mark_ranges(mark_ranges_), remaining_mark_ranges(mark_ranges_),
use_uncompressed_cache(use_uncompressed_cache_),
prewhere_actions(prewhere_actions_), prewhere_column(prewhere_column_),
log(&Logger::get("MergeTreeBlockInputStream")),
ordered_names{column_names},
min_bytes_to_use_direct_io(min_bytes_to_use_direct_io_), max_read_buffer_size(max_read_buffer_size_)
{
/** @note можно было бы просто поменять местами reverse в if и else ветках MergeTreeDataSelectExecutor,
* а этот reverse убрать. */
std::reverse(remaining_mark_ranges.begin(), remaining_mark_ranges.end());
/// inject columns required for defaults evaluation
const auto injected_columns = injectRequiredColumns(column_names);
should_reorder = !injected_columns.empty();
Names pre_column_names;
if (prewhere_actions)
{
pre_column_names = prewhere_actions->getRequiredColumns();
if (pre_column_names.empty())
pre_column_names.push_back(column_names[0]);
const auto injected_pre_columns = injectRequiredColumns(pre_column_names);
if (!injected_pre_columns.empty())
should_reorder = true;
const NameSet pre_name_set(pre_column_names.begin(), pre_column_names.end());
/// Если выражение в PREWHERE - не столбец таблицы, не нужно отдавать наружу столбец с ним
/// (от storage ожидают получить только столбцы таблицы).
remove_prewhere_column = !pre_name_set.count(prewhere_column);
Names post_column_names;
for (const auto & name : column_names)
if (!pre_name_set.count(name))
post_column_names.push_back(name);
column_names = post_column_names;
}
/// will be used to distinguish between PREWHERE and WHERE columns when applying filter
column_name_set = NameSet{column_names.begin(), column_names.end()};
if (check_columns)
{
/// Под owned_data_part->columns_lock проверим, что все запрошенные столбцы в куске того же типа, что в таблице.
/// Это может быть не так во время ALTER MODIFY.
if (!pre_column_names.empty())
storage.check(owned_data_part->columns, pre_column_names);
if (!column_names.empty())
storage.check(owned_data_part->columns, column_names);
pre_columns = storage.getColumnsList().addTypes(pre_column_names);
columns = storage.getColumnsList().addTypes(column_names);
}
else
{
pre_columns = owned_data_part->columns.addTypes(pre_column_names);
columns = owned_data_part->columns.addTypes(column_names);
}
/// Оценим общее количество строк - для прогресс-бара.
size_t total_rows = 0;
for (const auto & range : all_mark_ranges)
total_rows += range.end - range.begin;
total_rows *= storage.index_granularity;
LOG_TRACE(log, "Reading " << all_mark_ranges.size() << " ranges from part " << owned_data_part->name
<< ", approx. " << total_rows
<< (all_mark_ranges.size() > 1
? ", up to " + toString((all_mark_ranges.back().end - all_mark_ranges.front().begin) * storage.index_granularity)
: "")
<< " rows starting from " << all_mark_ranges.front().begin * storage.index_granularity);
setTotalRowsApprox(total_rows);
}
String getName() const override { return "MergeTree"; }
String getID() const override
{
std::stringstream res;
res << "MergeTree(" << path << ", columns";
for (const NameAndTypePair & column : columns)
res << ", " << column.name;
if (prewhere_actions)
res << ", prewhere, " << prewhere_actions->getID();
res << ", marks";
for (size_t i = 0; i < all_mark_ranges.size(); ++i)
res << ", " << all_mark_ranges[i].begin << ", " << all_mark_ranges[i].end;
res << ")";
return res.str();
}
protected:
/// Будем вызывать progressImpl самостоятельно.
void progress(const Progress & value) override {}
/** Если некоторых запрошенных столбцов нет в куске,
* то выясняем, какие столбцы может быть необходимо дополнительно прочитать,
* чтобы можно было вычислить DEFAULT выражение для этих столбцов.
* Добавляет их в columns.
*/
NameSet injectRequiredColumns(Names & columns) const
{
NameSet required_columns{std::begin(columns), std::end(columns)};
NameSet injected_columns;
auto all_column_files_missing = true;
for (size_t i = 0; i < columns.size(); ++i)
{
const auto & column_name = columns[i];
/// column has files and hence does not require evaluation
if (owned_data_part->hasColumnFiles(column_name))
{
all_column_files_missing = false;
continue;
}
const auto default_it = storage.column_defaults.find(column_name);
/// columns has no explicit default expression
if (default_it == std::end(storage.column_defaults))
continue;
/// collect identifiers required for evaluation
IdentifierNameSet identifiers;
default_it->second.expression->collectIdentifierNames(identifiers);
for (const auto & identifier : identifiers)
{
if (storage.hasColumn(identifier))
{
/// ensure each column is added only once
if (required_columns.count(identifier) == 0)
{
columns.emplace_back(identifier);
required_columns.emplace(identifier);
injected_columns.emplace(identifier);
}
}
}
}
/// If all files are missing read at least one column to determine correct column sizes
if (all_column_files_missing)
{
const auto minimum_size_column_name = owned_data_part->getMinimumSizeColumnName();
columns.push_back(minimum_size_column_name);
injected_columns.insert(minimum_size_column_name);
}
return injected_columns;
}
Block readImpl() override
{
Block res;
if (remaining_mark_ranges.empty())
return res;
if (!reader)
{
if (use_uncompressed_cache)
owned_uncompressed_cache = storage.context.getUncompressedCache();
owned_mark_cache = storage.context.getMarkCache();
reader.reset(new MergeTreeReader(
path, owned_data_part, columns, owned_uncompressed_cache.get(), owned_mark_cache.get(), storage,
all_mark_ranges, min_bytes_to_use_direct_io, max_read_buffer_size));
if (prewhere_actions)
pre_reader.reset(new MergeTreeReader(
path, owned_data_part, pre_columns, owned_uncompressed_cache.get(), owned_mark_cache.get(), storage,
all_mark_ranges, min_bytes_to_use_direct_io, max_read_buffer_size));
}
if (prewhere_actions)
{
do
{
/// Прочитаем полный блок столбцов, нужных для вычисления выражения в PREWHERE.
size_t space_left = std::max(1LU, block_size / storage.index_granularity);
MarkRanges ranges_to_read;
while (!remaining_mark_ranges.empty() && space_left)
{
MarkRange & range = remaining_mark_ranges.back();
size_t marks_to_read = std::min(range.end - range.begin, space_left);
pre_reader->readRange(range.begin, range.begin + marks_to_read, res);
ranges_to_read.push_back(MarkRange(range.begin, range.begin + marks_to_read));
space_left -= marks_to_read;
range.begin += marks_to_read;
if (range.begin == range.end)
remaining_mark_ranges.pop_back();
}
progressImpl(Progress(res.rowsInFirstColumn(), res.bytes()));
pre_reader->fillMissingColumns(res, ordered_names, should_reorder);
/// Вычислим выражение в PREWHERE.
prewhere_actions->execute(res);
ColumnPtr column = res.getByName(prewhere_column).column;
if (remove_prewhere_column)
res.erase(prewhere_column);
size_t pre_bytes = res.bytes();
/** Если фильтр - константа (например, написано PREWHERE 1),
* то либо вернём пустой блок, либо вернём блок без изменений.
*/
if (ColumnConstUInt8 * column_const = typeid_cast<ColumnConstUInt8 *>(&*column))
{
if (!column_const->getData())
{
res.clear();
return res;
}
for (size_t i = 0; i < ranges_to_read.size(); ++i)
{
const MarkRange & range = ranges_to_read[i];
reader->readRange(range.begin, range.end, res);
}
progressImpl(Progress(0, res.bytes() - pre_bytes));
}
else if (ColumnUInt8 * column_vec = typeid_cast<ColumnUInt8 *>(&*column))
{
size_t index_granularity = storage.index_granularity;
const IColumn::Filter & pre_filter = column_vec->getData();
IColumn::Filter post_filter(pre_filter.size());
/// Прочитаем в нужных отрезках остальные столбцы и составим для них свой фильтр.
size_t pre_filter_pos = 0;
size_t post_filter_pos = 0;
for (size_t i = 0; i < ranges_to_read.size(); ++i)
{
const MarkRange & range = ranges_to_read[i];
size_t begin = range.begin;
size_t pre_filter_begin_pos = pre_filter_pos;
for (size_t mark = range.begin; mark <= range.end; ++mark)
{
UInt8 nonzero = 0;
if (mark != range.end)
{
size_t limit = std::min(pre_filter.size(), pre_filter_pos + index_granularity);
for (size_t row = pre_filter_pos; row < limit; ++row)
nonzero |= pre_filter[row];
}
if (!nonzero)
{
if (mark > begin)
{
memcpy(
&post_filter[post_filter_pos],
&pre_filter[pre_filter_begin_pos],
pre_filter_pos - pre_filter_begin_pos);
post_filter_pos += pre_filter_pos - pre_filter_begin_pos;
reader->readRange(begin, mark, res);
}
begin = mark + 1;
pre_filter_begin_pos = std::min(pre_filter_pos + index_granularity, pre_filter.size());
}
if (mark < range.end)
pre_filter_pos = std::min(pre_filter_pos + index_granularity, pre_filter.size());
}
}
if (!post_filter_pos)
{
res.clear();
continue;
}
progressImpl(Progress(0, res.bytes() - pre_bytes));
post_filter.resize(post_filter_pos);
/// Отфильтруем столбцы, относящиеся к PREWHERE, используя pre_filter,
/// остальные столбцы - используя post_filter.
size_t rows = 0;
for (size_t i = 0; i < res.columns(); ++i)
{
ColumnWithTypeAndName & column = res.getByPosition(i);
if (column.name == prewhere_column && res.columns() > 1)
continue;
column.column = column.column->filter(column_name_set.count(column.name) ? post_filter : pre_filter);
rows = column.column->size();
}
/// Заменим столбец со значением условия из PREWHERE на константу.
if (!remove_prewhere_column)
res.getByName(prewhere_column).column = new ColumnConstUInt8(rows, 1);
}
else
throw Exception("Illegal type " + column->getName() + " of column for filter. Must be ColumnUInt8 or ColumnConstUInt8.", ErrorCodes::ILLEGAL_TYPE_OF_COLUMN_FOR_FILTER);
reader->fillMissingColumnsAndReorder(res, ordered_names);
}
while (!remaining_mark_ranges.empty() && !res && !isCancelled());
}
else
{
size_t space_left = std::max(1LU, block_size / storage.index_granularity);
while (!remaining_mark_ranges.empty() && space_left)
{
MarkRange & range = remaining_mark_ranges.back();
size_t marks_to_read = std::min(range.end - range.begin, space_left);
reader->readRange(range.begin, range.begin + marks_to_read, res);
space_left -= marks_to_read;
range.begin += marks_to_read;
if (range.begin == range.end)
remaining_mark_ranges.pop_back();
}
progressImpl(Progress(res.rowsInFirstColumn(), res.bytes()));
reader->fillMissingColumns(res, ordered_names);
}
if (remaining_mark_ranges.empty())
{
/** Закрываем файлы (ещё до уничтожения объекта).
* Чтобы при создании многих источников, но одновременном чтении только из нескольких,
* буферы не висели в памяти.
*/
reader.reset();
pre_reader.reset();
part_columns_lock.reset();
owned_data_part.reset();
}
return res;
}
private:
const String path;
size_t block_size;
NamesAndTypesList columns;
NameSet column_name_set;
NamesAndTypesList pre_columns;
MergeTreeData & storage;
MergeTreeData::DataPartPtr owned_data_part; /// Кусок не будет удалён, пока им владеет этот объект.
std::unique_ptr<Poco::ScopedReadRWLock> part_columns_lock; /// Не дадим изменить список столбцов куска, пока мы из него читаем.
MarkRanges all_mark_ranges; /// В каких диапазонах засечек читать. В порядке возрастания номеров.
MarkRanges remaining_mark_ranges; /// В каких диапазонах засечек еще не прочли.
/// В порядке убывания номеров, чтобы можно было выбрасывать из конца.
bool use_uncompressed_cache;
std::unique_ptr<MergeTreeReader> reader;
std::unique_ptr<MergeTreeReader> pre_reader;
ExpressionActionsPtr prewhere_actions;
String prewhere_column;
bool remove_prewhere_column;
Logger * log;
/// column names in specific order as expected by other stages
Names ordered_names;
bool should_reorder{false};
size_t min_bytes_to_use_direct_io;
size_t max_read_buffer_size;
UncompressedCachePtr owned_uncompressed_cache;
MarkCachePtr owned_mark_cache;
};
}