#pragma once #include namespace DB { class IStorage; /// Snapshot of storage that fixes set columns that can be read in query. /// There are 3 sources of columns: regular columns from metadata, /// dynamic columns from object Types, virtual columns. struct StorageSnapshot { const IStorage & storage; const StorageMetadataPtr metadata; const ColumnsDescription object_columns; /// Additional data, on which set of columns may depend. /// E.g. data parts in MergeTree, list of blocks in Memory, etc. struct Data { virtual ~Data() = default; }; using DataPtr = std::unique_ptr; DataPtr data; /// Projection that is used in query. mutable const ProjectionDescription * projection = nullptr; StorageSnapshot( const IStorage & storage_, const StorageMetadataPtr & metadata_) : storage(storage_), metadata(metadata_) { init(); } StorageSnapshot( const IStorage & storage_, const StorageMetadataPtr & metadata_, const ColumnsDescription & object_columns_) : storage(storage_), metadata(metadata_), object_columns(object_columns_) { init(); } StorageSnapshot( const IStorage & storage_, const StorageMetadataPtr & metadata_, const ColumnsDescription & object_columns_, DataPtr data_) : storage(storage_), metadata(metadata_), object_columns(object_columns_), data(std::move(data_)) { init(); } /// Get all available columns with types according to options. NamesAndTypesList getColumns(const GetColumnsOptions & options) const; /// Get columns with types according to options only for requested names. NamesAndTypesList getColumnsByNames(const GetColumnsOptions & options, const Names & names) const; /// Get column with type according to options for requested name. std::optional tryGetColumn(const GetColumnsOptions & options, const String & column_name) const; NameAndTypePair getColumn(const GetColumnsOptions & options, const String & column_name) const; /// Block with ordinary + materialized + aliases + virtuals + subcolumns. Block getSampleBlockForColumns(const Names & column_names) const; ColumnsDescription getDescriptionForColumns(const Names & column_names) const; /// Verify that all the requested names are in the table and are set correctly: /// list of names is not empty and the names do not repeat. void check(const Names & column_names) const; DataTypePtr getConcreteType(const String & column_name) const; void addProjection(const ProjectionDescription * projection_) const { projection = projection_; } /// If we have a projection then we should use its metadata. StorageMetadataPtr getMetadataForQuery() const { return projection ? projection->metadata : metadata; } private: void init(); std::unordered_map virtual_columns; }; using StorageSnapshotPtr = std::shared_ptr; }