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73 lines
2.5 KiB
C++
73 lines
2.5 KiB
C++
#pragma once
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#include <ext/shared_ptr_helper.h>
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#include <Common/OptimizedRegularExpression.h>
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#include <Storages/IStorage.h>
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namespace DB
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{
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/** A table that represents the union of an arbitrary number of other tables.
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* All tables must have the same structure.
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*/
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class StorageMerge : public ext::shared_ptr_helper<StorageMerge>, public IStorage
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{
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public:
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std::string getName() const override { return "Merge"; }
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std::string getTableName() const override { return name; }
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bool isRemote() const override;
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/// The check is delayed to the read method. It checks the support of the tables used.
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bool supportsSampling() const override { return true; }
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bool supportsPrewhere() const override { return true; }
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bool supportsFinal() const override { return true; }
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bool supportsIndexForIn() const override { return true; }
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const NamesAndTypesList & getColumnsListImpl() const override { return columns; }
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NameAndTypePair getColumn(const String & column_name) const override;
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bool hasColumn(const String & column_name) const override;
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BlockInputStreams read(
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const Names & column_names,
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const SelectQueryInfo & query_info,
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const Context & context,
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QueryProcessingStage::Enum & processed_stage,
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size_t max_block_size,
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unsigned num_streams) override;
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void drop() override {}
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void rename(const String & /*new_path_to_db*/, const String & /*new_database_name*/, const String & new_table_name) override { name = new_table_name; }
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/// you need to add and remove columns in the sub-tables manually
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/// the structure of sub-tables is not checked
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void alter(const AlterCommands & params, const String & database_name, const String & table_name, const Context & context) override;
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private:
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String name;
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String source_database;
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OptimizedRegularExpression table_name_regexp;
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const Context & context;
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using StorageListWithLocks = std::list<std::pair<StoragePtr, TableStructureReadLockPtr>>;
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StorageListWithLocks getSelectedTables() const;
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Block getBlockWithVirtualColumns(const StorageListWithLocks & selected_tables) const;
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protected:
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StorageMerge(
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const std::string & name_,
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const NamesAndTypesList & columns_,
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const NamesAndTypesList & materialized_columns_,
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const NamesAndTypesList & alias_columns_,
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const ColumnDefaults & column_defaults_,
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const String & source_database_,
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const String & table_name_regexp_,
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const Context & context_);
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};
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}
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