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123 lines
4.3 KiB
C++
123 lines
4.3 KiB
C++
#pragma once
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#include <map>
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#include <shared_mutex>
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#include <ext/shared_ptr_helper.h>
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#include <Disks/IDisk.h>
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#include <Storages/IStorage.h>
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#include <Common/FileChecker.h>
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#include <Common/escapeForFileName.h>
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#include <Core/NamesAndTypes.h>
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namespace DB
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{
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/** Implements simple table engine without support of indices.
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* The data is stored in a compressed form.
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*/
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class StorageLog final : public ext::shared_ptr_helper<StorageLog>, public IStorage
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{
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friend class LogSource;
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friend class LogBlockOutputStream;
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friend struct ext::shared_ptr_helper<StorageLog>;
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public:
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String getName() const override { return "Log"; }
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Pipe read(
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const Names & column_names,
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const StorageMetadataPtr & metadata_snapshot,
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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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BlockOutputStreamPtr write(const ASTPtr & query, const StorageMetadataPtr & /*metadata_snapshot*/, const Context & context) override;
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void rename(const String & new_path_to_table_data, const StorageID & new_table_id) override;
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CheckResults checkData(const ASTPtr & /* query */, const Context & /* context */) override;
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void truncate(const ASTPtr &, const StorageMetadataPtr & metadata_snapshot, const Context &, TableExclusiveLockHolder &) override;
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bool storesDataOnDisk() const override { return true; }
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Strings getDataPaths() const override { return {DB::fullPath(disk, table_path)}; }
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bool supportsSubcolumns() const override { return true; }
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protected:
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/** Attach the table with the appropriate name, along the appropriate path (with / at the end),
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* (the correctness of names and paths is not verified)
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* consisting of the specified columns; Create files if they do not exist.
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*/
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StorageLog(
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DiskPtr disk_,
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const std::string & relative_path_,
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const StorageID & table_id_,
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const ColumnsDescription & columns_,
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const ConstraintsDescription & constraints_,
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bool attach,
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size_t max_compress_block_size_);
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private:
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/** Offsets to some row number in a file for column in table.
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* They are needed so that you can read the data in several threads.
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*/
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struct Mark
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{
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size_t rows; /// How many rows are before this offset including the block at this offset.
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size_t offset; /// The offset in compressed file.
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};
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using Marks = std::vector<Mark>;
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/// Column data
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struct ColumnData
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{
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/// Specifies the column number in the marks file.
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/// Does not necessarily match the column number among the columns of the table: columns with lengths of arrays are also numbered here.
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size_t column_index;
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String data_file_path;
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Marks marks;
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};
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using Files = std::map<String, ColumnData>; /// file name -> column data
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DiskPtr disk;
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String table_path;
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mutable std::shared_timed_mutex rwlock;
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Files files;
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Names column_names_by_idx; /// column_index -> name
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String marks_file_path;
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/// The order of adding files should not change: it corresponds to the order of the columns in the marks file.
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void addFiles(const NameAndTypePair & column);
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bool loaded_marks = false;
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size_t max_compress_block_size;
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size_t file_count = 0;
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FileChecker file_checker;
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/// Read marks files if they are not already read.
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/// It is done lazily, so that with a large number of tables, the server starts quickly.
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/// You can not call with a write locked `rwlock`.
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void loadMarks(std::chrono::seconds lock_timeout);
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/** For normal columns, the number of rows in the block is specified in the marks.
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* For array columns and nested structures, there are more than one group of marks that correspond to different files
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* - for elements (file name.bin) - the total number of array elements in the block is specified,
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* - for array sizes (file name.size0.bin) - the number of rows (the whole arrays themselves) in the block is specified.
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*
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* Return the first group of marks that contain the number of rows, but not the internals of the arrays.
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*/
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const Marks & getMarksWithRealRowCount(const StorageMetadataPtr & metadata_snapshot) const;
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};
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}
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