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97 lines
3.1 KiB
C++
97 lines
3.1 KiB
C++
#include <Interpreters/InterpreterSelectQuery.h>
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#include <Interpreters/InterpreterSelectWithUnionQuery.h>
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#include <Parsers/ASTCreateQuery.h>
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#include <Parsers/ASTSubquery.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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#include <Common/typeid_cast.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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extern const int LOGICAL_ERROR;
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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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checkQueryProcessingStage(processed_stage, context);
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BlockInputStreams res;
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if (context.getSettings().enable_optimize_predicate_expression)
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{
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replaceTableNameWithSubquery(typeid_cast<ASTSelectQuery *>(query_info.query.get()), inner_query);
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auto res_io = InterpreterSelectQuery(query_info.query, context, column_names, processed_stage).execute();
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res.emplace_back(res_io.in);
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return res;
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}
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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 StorageView::replaceTableNameWithSubquery(ASTSelectQuery * select_query, ASTPtr & subquery)
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{
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ASTTablesInSelectQueryElement * select_element = static_cast<ASTTablesInSelectQueryElement *>(select_query->tables->children[0].get());
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if (!select_element->table_expression)
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throw Exception("Logical error: incorrect table expression", ErrorCodes::LOGICAL_ERROR);
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ASTTableExpression * table_expression = static_cast<ASTTableExpression *>(select_element->table_expression.get());
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if (!table_expression->database_and_table_name)
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throw Exception("Logical error: incorrect table expression", ErrorCodes::LOGICAL_ERROR);
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table_expression->database_and_table_name = {};
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table_expression->subquery = std::make_shared<ASTSubquery>();
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table_expression->subquery->children.push_back(subquery->clone());
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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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