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64 lines
1.8 KiB
C++
64 lines
1.8 KiB
C++
#include <Interpreters/InterpreterSelectWithUnionQuery.h>
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#include <Parsers/ASTCreateQuery.h>
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#include <Storages/StorageView.h>
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#include <Storages/StorageFactory.h>
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#include <DataStreams/MaterializingBlockInputStream.h>
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namespace DB
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{
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namespace ErrorCodes
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{
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extern const int INCORRECT_QUERY;
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}
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StorageView::StorageView(
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const String & table_name_,
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const ASTCreateQuery & query,
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const ColumnsDescription & columns_)
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: IStorage{columns_}, table_name(table_name_)
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{
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if (!query.select)
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throw Exception("SELECT query is not specified for " + getName(), ErrorCodes::INCORRECT_QUERY);
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inner_query = query.select->ptr();
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}
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BlockInputStreams StorageView::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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const size_t /*max_block_size*/,
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const unsigned /*num_streams*/)
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{
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processed_stage = QueryProcessingStage::FetchColumns;
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BlockInputStreams res = InterpreterSelectWithUnionQuery(inner_query, context, column_names).executeWithMultipleStreams();
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/// It's expected that the columns read from storage are not constant.
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/// Because method 'getSampleBlockForColumns' is used to obtain a structure of result in InterpreterSelectQuery.
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for (auto & stream : res)
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stream = std::make_shared<MaterializingBlockInputStream>(stream);
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return res;
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}
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void registerStorageView(StorageFactory & factory)
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{
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factory.registerStorage("View", [](const StorageFactory::Arguments & args)
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{
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if (args.query.storage)
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throw Exception("Specifying ENGINE is not allowed for a View", ErrorCodes::INCORRECT_QUERY);
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return StorageView::create(args.table_name, args.query, args.columns);
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});
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}
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}
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