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58 lines
1.7 KiB
C++
58 lines
1.7 KiB
C++
#pragma once
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#include <DataTypes/DataTypeString.h>
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#include <Storages/ColumnsDescription.h>
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#include <Storages/IStorage.h>
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#include <ext/shared_ptr_helper.h>
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#include <Processors/Sources/SourceFromSingleChunk.h>
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#include <Processors/Pipe.h>
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namespace DB
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{
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class Context;
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/** Base class for system tables whose all columns have String type.
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*/
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template <typename Self>
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class IStorageSystemOneBlock : public IStorage
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{
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protected:
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virtual void fillData(MutableColumns & res_columns, const Context & context, const SelectQueryInfo & query_info) const = 0;
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public:
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#if defined(ARCADIA_BUILD)
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IStorageSystemOneBlock(const String & name_) : IStorageSystemOneBlock(StorageID{"system", name_}) {}
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#endif
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IStorageSystemOneBlock(const StorageID & table_id_) : IStorage(table_id_)
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{
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StorageInMemoryMetadata metadata_;
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metadata_.setColumns(ColumnsDescription(Self::getNamesAndTypes()));
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setInMemoryMetadata(metadata_);
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}
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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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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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{
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metadata_snapshot->check(column_names, getVirtuals(), getStorageID());
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Block sample_block = metadata_snapshot->getSampleBlock();
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MutableColumns res_columns = sample_block.cloneEmptyColumns();
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fillData(res_columns, context, query_info);
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UInt64 num_rows = res_columns.at(0)->size();
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Chunk chunk(std::move(res_columns), num_rows);
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return Pipe(std::make_shared<SourceFromSingleChunk>(sample_block, std::move(chunk)));
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}
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};
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}
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