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90 lines
3.6 KiB
C++
90 lines
3.6 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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friend struct ext::shared_ptr_helper<StorageMerge>;
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public:
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std::string getName() const override { return "Merge"; }
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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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/// Consider columns coming from the underlying tables
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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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QueryProcessingStage::Enum getQueryProcessingStage(const Context &) 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 checkAlterIsPossible(const AlterCommands & commands, const Settings & /* settings */) override;
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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 Context & context, TableStructureWriteLockHolder & table_lock_holder) override;
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bool mayBenefitFromIndexForIn(const ASTPtr & left_in_operand, const Context & query_context) const override;
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private:
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String source_database;
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OptimizedRegularExpression table_name_regexp;
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Context global_context;
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using StorageWithLockAndName = std::tuple<StoragePtr, TableStructureReadLockHolder, String>;
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using StorageListWithLocks = std::list<StorageWithLockAndName>;
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StorageListWithLocks getSelectedTables(const String & query_id) const;
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StorageMerge::StorageListWithLocks getSelectedTables(const ASTPtr & query, bool has_virtual_column, const String & query_id) const;
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template <typename F>
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StoragePtr getFirstTable(F && predicate) const;
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DatabaseTablesIteratorPtr getDatabaseIterator(const Context & context) const;
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protected:
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StorageMerge(
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const StorageID & table_id_,
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const ColumnsDescription & columns_,
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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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Block getQueryHeader(const Names & column_names, const SelectQueryInfo & query_info,
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const Context & context, QueryProcessingStage::Enum processed_stage);
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BlockInputStreams createSourceStreams(const SelectQueryInfo & query_info, const QueryProcessingStage::Enum & processed_stage,
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const UInt64 max_block_size, const Block & header, const StorageWithLockAndName & storage_with_lock,
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Names & real_column_names,
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Context & modified_context, size_t streams_num, bool has_table_virtual_column,
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bool concat_streams = false);
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void convertingSourceStream(const Block & header, const Context & context, ASTPtr & query,
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BlockInputStreamPtr & source_stream, QueryProcessingStage::Enum processed_stage);
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};
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}
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