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https://github.com/ClickHouse/ClickHouse.git
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330212e0f4
The original motivation for this commit was that shared_ptr_helper used std::shared_ptr<>() which does two heap allocations instead of make_shared<>() which does a single allocation. Turned out that 1. the affected code (--> Storages/) is not on a hot path (rendering the performance argument moot ...) 2. yet copying Storage objects is potentially dangerous and was previously allowed. Hence, this change - removes shared_ptr_helper and as a result all inherited create() methods, - instead, Storage objects are now created using make_shared<>() by the caller (for that to work, many constructors had to be made public), and - all Storage classes were marked as noncopyable using boost::noncopyable. In sum, we are (likely) not making things faster but the code becomes cleaner and harder to misuse.
62 lines
2.1 KiB
C++
62 lines
2.1 KiB
C++
#include <TableFunctions/ITableFunction.h>
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#include <TableFunctions/TableFunctionZeros.h>
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#include <TableFunctions/TableFunctionFactory.h>
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#include <Parsers/ASTFunction.h>
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#include <Parsers/ASTLiteral.h>
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#include <Storages/System/StorageSystemZeros.h>
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#include <DataTypes/DataTypesNumber.h>
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#include <Interpreters/evaluateConstantExpression.h>
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#include <Interpreters/Context.h>
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#include "registerTableFunctions.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 NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
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}
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template <bool multithreaded>
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ColumnsDescription TableFunctionZeros<multithreaded>::getActualTableStructure(ContextPtr /*context*/) const
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{
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/// NOTE: https://bugs.llvm.org/show_bug.cgi?id=47418
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return ColumnsDescription{{{"zero", std::make_shared<DataTypeUInt8>()}}};
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}
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template <bool multithreaded>
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StoragePtr TableFunctionZeros<multithreaded>::executeImpl(const ASTPtr & ast_function, ContextPtr context, const std::string & table_name, ColumnsDescription /*cached_columns*/) const
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{
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if (const auto * function = ast_function->as<ASTFunction>())
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{
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auto arguments = function->arguments->children;
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if (arguments.size() != 1)
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throw Exception("Table function '" + getName() + "' requires 'length'.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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UInt64 length = evaluateArgument(context, arguments[0]);
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auto res = std::make_shared<StorageSystemZeros>(StorageID(getDatabaseName(), table_name), multithreaded, length);
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res->startup();
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return res;
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}
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throw Exception("Table function '" + getName() + "' requires 'limit'.", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
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}
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void registerTableFunctionZeros(TableFunctionFactory & factory)
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{
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factory.registerFunction<TableFunctionZeros<true>>();
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factory.registerFunction<TableFunctionZeros<false>>();
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}
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template <bool multithreaded>
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UInt64 TableFunctionZeros<multithreaded>::evaluateArgument(ContextPtr context, ASTPtr & argument) const
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{
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return evaluateConstantExpressionOrIdentifierAsLiteral(argument, context)->as<ASTLiteral &>().value.safeGet<UInt64>();
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}
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}
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