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