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263 lines
9.7 KiB
C++
263 lines
9.7 KiB
C++
#pragma once
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#include <DB/Core/NamesAndTypes.h>
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#include <DB/Storages/MergeTree/RangesInDataPart.h>
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#include <statdaemons/ext/range.hpp>
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#include <mutex>
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namespace DB
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{
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struct MergeTreeReadTask
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{
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MergeTreeData::DataPartPtr data_part;
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MarkRanges mark_ranges;
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std::size_t part_index_in_query;
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const Names & ordered_names;
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const NameSet & column_name_set;
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const NamesAndTypesList & columns;
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const NamesAndTypesList & pre_columns;
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const bool remove_prewhere_column;
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const MarkRanges & all_ranges;
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MergeTreeReadTask(const MergeTreeData::DataPartPtr & data_part, const MarkRanges & ranges,
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const std::size_t part_index_in_query, const Names & ordered_names,
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const NameSet & column_name_set, const NamesAndTypesList & columns,
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const NamesAndTypesList & pre_columns, const bool remove_prewhere_column,
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const MarkRanges & all_ranges)
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: data_part{data_part}, mark_ranges{ranges}, part_index_in_query{part_index_in_query},
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ordered_names{ordered_names}, column_name_set{column_name_set}, columns{columns}, pre_columns{pre_columns},
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remove_prewhere_column{remove_prewhere_column}, all_ranges{all_ranges}
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{}
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};
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using MergeTreeReadTaskPtr = std::unique_ptr<MergeTreeReadTask>;
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class MergeTreeReadPool
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{
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public:
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MergeTreeReadPool(const RangesInDataParts & parts, const std::vector<std::size_t> & per_part_sum_marks,
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const std::size_t sum_marks, MergeTreeData & data, const ExpressionActionsPtr & prewhere_actions,
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const String & prewhere_column_name, const bool check_columns, const Names & column_names)
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: parts{parts}, per_part_sum_marks{per_part_sum_marks}, sum_marks{sum_marks}, data{data}
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{
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fillPerPartInfo(column_names, prewhere_actions, prewhere_column_name, check_columns);
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}
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MergeTreeReadPool(const MergeTreeReadPool &) = delete;
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MergeTreeReadPool & operator=(const MergeTreeReadPool &) = delete;
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MergeTreeReadTaskPtr getTask(const std::size_t min_marks_to_read)
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{
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const std::lock_guard<std::mutex> lock{mutex};
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if (0 == sum_marks)
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return nullptr;
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/// @todo use map to speedup lookup
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/// find a part which has marks remaining
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std::size_t part_id = 0;
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for (; part_id < parts.size(); ++part_id)
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if (0 != per_part_sum_marks[part_id])
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break;
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auto & part = parts[part_id];
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const auto & ordered_names = per_part_ordered_names[part_id];
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const auto & column_name_set = per_part_column_name_set[part_id];
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const auto & columns = per_part_columns[part_id];
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const auto & pre_columns = per_part_pre_columns[part_id];
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const auto remove_prewhere_column = per_part_remove_prewhere_column[part_id];
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auto & marks_in_part = per_part_sum_marks[part_id];
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/// Берём весь кусок, если он достаточно мал
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auto need_marks = std::min(marks_in_part, min_marks_to_read);
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/// Не будем оставлять в куске слишком мало строк.
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if (marks_in_part > need_marks &&
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marks_in_part - need_marks < min_marks_to_read)
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need_marks = marks_in_part;
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MarkRanges ranges_to_get_from_part;
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/// Возьмем весь кусок, если он достаточно мал.
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if (marks_in_part <= need_marks)
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{
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const auto marks_to_get_from_range = marks_in_part;
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/// Восстановим порядок отрезков.
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std::reverse(part.ranges.begin(), part.ranges.end());
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ranges_to_get_from_part = part.ranges;
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marks_in_part -= marks_to_get_from_range;
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sum_marks -= marks_to_get_from_range;
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}
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else
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{
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/// Цикл по отрезкам куска.
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while (need_marks > 0 && !part.ranges.empty())
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{
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auto & range = part.ranges.back();
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const std::size_t marks_in_range = range.end - range.begin;
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const std::size_t marks_to_get_from_range = std::min(marks_in_range, need_marks);
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ranges_to_get_from_part.emplace_back(range.begin, range.begin + marks_to_get_from_range);
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range.begin += marks_to_get_from_range;
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if (range.begin == range.end)
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part.ranges.pop_back();
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marks_in_part -= marks_to_get_from_range;
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need_marks -= marks_to_get_from_range;
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sum_marks -= marks_to_get_from_range;
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}
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}
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return std::make_unique<MergeTreeReadTask>(
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part.data_part, ranges_to_get_from_part, part.part_index_in_query, ordered_names, column_name_set, columns,
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pre_columns, remove_prewhere_column, per_part_all_ranges[part_id]);
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}
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public:
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void fillPerPartInfo(const Names & column_names, const ExpressionActionsPtr & prewhere_actions,
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const String & prewhere_column_name, const bool check_columns)
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{
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for (const auto & part : parts)
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{
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per_part_all_ranges.push_back(part.ranges);
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per_part_columns_lock.push_back(std::make_unique<Poco::ScopedReadRWLock>(
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part.data_part->columns_lock));
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/// inject column names required for DEFAULT evaluation in current part
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auto required_column_names = column_names;
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const auto injected_columns = injectRequiredColumns(part.data_part, required_column_names);
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/// insert injected columns into ordered columns list to avoid exception about different block structures
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auto ordered_names = column_names;
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ordered_names.insert(std::end(ordered_names), std::begin(injected_columns), std::end(injected_columns));
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per_part_ordered_names.emplace_back(ordered_names);
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Names required_pre_column_names;
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if (prewhere_actions)
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{
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/// collect columns required for PREWHERE evaluation
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/// @todo minimum size column may be added here due to const condition, thus invalidating ordered_names
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required_pre_column_names = prewhere_actions->getRequiredColumns();
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/// there must be at least one column required for PREWHERE
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if (required_pre_column_names.empty())
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required_pre_column_names.push_back(required_column_names[0]);
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/// PREWHERE columns may require some additional columns for DEFAULT evaluation
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(void) injectRequiredColumns(part.data_part, required_pre_column_names);
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/// will be used to distinguish between PREWHERE and WHERE columns when applying filter
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const NameSet pre_name_set{
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std::begin(required_pre_column_names), std::end(required_pre_column_names)
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};
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/** Если выражение в PREWHERE - не столбец таблицы, не нужно отдавать наружу столбец с ним
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* (от storage ожидают получить только столбцы таблицы). */
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per_part_remove_prewhere_column.push_back(0 == pre_name_set.count(prewhere_column_name));
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Names post_column_names;
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for (const auto & name : required_column_names)
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if (!pre_name_set.count(name))
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post_column_names.push_back(name);
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required_column_names = post_column_names;
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}
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else
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per_part_remove_prewhere_column.push_back(false);
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per_part_column_name_set.emplace_back(std::begin(required_column_names), std::end(required_column_names));
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if (check_columns)
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{
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/** Под part->columns_lock проверим, что все запрошенные столбцы в куске того же типа, что в таблице.
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* Это может быть не так во время ALTER MODIFY. */
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if (!required_pre_column_names.empty())
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data.check(part.data_part->columns, required_pre_column_names);
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if (!required_column_names.empty())
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data.check(part.data_part->columns, required_column_names);
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per_part_pre_columns.push_back(data.getColumnsList().addTypes(required_pre_column_names));
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per_part_columns.push_back(data.getColumnsList().addTypes(required_column_names));
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}
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else
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{
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per_part_pre_columns.push_back(part.data_part->columns.addTypes(required_pre_column_names));
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per_part_columns.push_back(part.data_part->columns.addTypes(required_column_names));
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}
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}
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}
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/** Если некоторых запрошенных столбцов нет в куске,
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* то выясняем, какие столбцы может быть необходимо дополнительно прочитать,
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* чтобы можно было вычислить DEFAULT выражение для этих столбцов.
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* Добавляет их в columns. */
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NameSet injectRequiredColumns(const MergeTreeData::DataPartPtr & part, Names & columns) const
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{
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NameSet required_columns{std::begin(columns), std::end(columns)};
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NameSet injected_columns;
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for (size_t i = 0; i < columns.size(); ++i)
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{
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const auto & column_name = columns[i];
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/// column has files and hence does not require evaluation
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if (part->hasColumnFiles(column_name))
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continue;
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const auto default_it = data.column_defaults.find(column_name);
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/// columns has no explicit default expression
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if (default_it == std::end(data.column_defaults))
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continue;
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/// collect identifiers required for evaluation
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IdentifierNameSet identifiers;
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default_it->second.expression->collectIdentifierNames(identifiers);
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for (const auto & identifier : identifiers)
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{
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if (data.hasColumn(identifier))
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{
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/// ensure each column is added only once
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if (required_columns.count(identifier) == 0)
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{
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columns.emplace_back(identifier);
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required_columns.emplace(identifier);
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injected_columns.emplace(identifier);
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}
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}
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}
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}
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return injected_columns;
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}
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std::vector<std::unique_ptr<Poco::ScopedReadRWLock>> per_part_columns_lock;
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RangesInDataParts parts;
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std::vector<MarkRanges> per_part_all_ranges;
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std::vector<std::size_t> per_part_sum_marks;
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std::size_t sum_marks;
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MergeTreeData & data;
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std::vector<Names> per_part_ordered_names;
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std::vector<NameSet> per_part_column_name_set;
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std::vector<NamesAndTypesList> per_part_columns;
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std::vector<NamesAndTypesList> per_part_pre_columns;
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/// @todo actually all of these values are either true or false for the whole query, thus no vector required
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std::vector<bool> per_part_remove_prewhere_column;
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mutable std::mutex mutex;
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};
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using MergeTreeReadPoolPtr = std::shared_ptr<MergeTreeReadPool>;
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}
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