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74 lines
2.4 KiB
C++
74 lines
2.4 KiB
C++
#pragma once
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#include <Storages/MergeTree/MergeTreeBaseSelectProcessor.h>
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#include <Storages/MergeTree/MergeTreeData.h>
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#include <Storages/MergeTree/MarkRange.h>
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#include <Storages/MergeTree/MergeTreeBlockReadUtils.h>
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#include <Storages/SelectQueryInfo.h>
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namespace DB
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{
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/// Used to read data from single part with select query
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/// Cares about PREWHERE, virtual columns, indexes etc.
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/// To read data from multiple parts, Storage (MergeTree) creates multiple such objects.
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class MergeTreeSelectProcessor : public MergeTreeBaseSelectProcessor
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{
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public:
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MergeTreeSelectProcessor(
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const MergeTreeData & storage,
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const StorageMetadataPtr & metadata_snapshot,
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const MergeTreeData::DataPartPtr & owned_data_part,
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UInt64 max_block_size_rows,
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size_t preferred_block_size_bytes,
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size_t preferred_max_column_in_block_size_bytes,
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Names required_columns_,
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MarkRanges mark_ranges,
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bool use_uncompressed_cache,
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const PrewhereInfoPtr & prewhere_info,
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ExpressionActionsSettings actions_settings,
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bool check_columns_,
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const MergeTreeReaderSettings & reader_settings,
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const Names & virt_column_names = {},
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size_t part_index_in_query_ = 0,
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bool has_limit_below_one_block_ = false);
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~MergeTreeSelectProcessor() override;
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/// Closes readers and unlock part locks
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void finish();
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protected:
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/// Defer initialization from constructor, because it may be heavy
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/// and it's better to do it lazily in `getNewTask`, which is executing in parallel.
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void initializeReaders();
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/// Used by Task
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Names required_columns;
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/// Names from header. Used in order to order columns in read blocks.
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Names ordered_names;
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NameSet column_name_set;
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MergeTreeReadTaskColumns task_columns;
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/// Data part will not be removed if the pointer owns it
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MergeTreeData::DataPartPtr data_part;
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/// Cache getSampleBlock call, which might be heavy.
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Block sample_block;
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/// Mark ranges we should read (in ascending order)
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MarkRanges all_mark_ranges;
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/// Value of _part_index virtual column (used only in SelectExecutor)
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size_t part_index_in_query = 0;
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/// If true, every task will be created only with one range.
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/// It reduces amount of read data for queries with small LIMIT.
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bool has_limit_below_one_block = false;
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bool check_columns;
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size_t total_rows = 0;
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};
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}
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