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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
1.8 KiB
C++
62 lines
1.8 KiB
C++
#include <Interpreters/InterpreterSelectWithUnionQuery.h>
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#include <Parsers/ASTFunction.h>
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#include <Parsers/ASTSelectWithUnionQuery.h>
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#include <Storages/StorageView.h>
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#include <TableFunctions/ITableFunction.h>
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#include <TableFunctions/TableFunctionFactory.h>
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#include <TableFunctions/TableFunctionView.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 BAD_ARGUMENTS;
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}
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const ASTSelectWithUnionQuery & TableFunctionView::getSelectQuery() const
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{
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return *create.select;
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}
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void TableFunctionView::parseArguments(const ASTPtr & ast_function, ContextPtr /*context*/)
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{
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const auto * function = ast_function->as<ASTFunction>();
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if (function)
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{
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if (auto * select = function->tryGetQueryArgument())
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{
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create.set(create.select, select->clone());
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return;
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}
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}
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throw Exception("Table function '" + getName() + "' requires a query argument.", ErrorCodes::BAD_ARGUMENTS);
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}
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ColumnsDescription TableFunctionView::getActualTableStructure(ContextPtr context) const
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{
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assert(create.select);
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assert(create.children.size() == 1);
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assert(create.children[0]->as<ASTSelectWithUnionQuery>());
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auto sample = InterpreterSelectWithUnionQuery::getSampleBlock(create.children[0], context);
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return ColumnsDescription(sample.getNamesAndTypesList());
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}
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StoragePtr TableFunctionView::executeImpl(
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const ASTPtr & /*ast_function*/, ContextPtr context, const std::string & table_name, ColumnsDescription /*cached_columns*/) const
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{
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auto columns = getActualTableStructure(context);
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auto res = std::make_shared<StorageView>(StorageID(getDatabaseName(), table_name), create, columns, "");
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res->startup();
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return res;
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}
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void registerTableFunctionView(TableFunctionFactory & factory)
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{
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factory.registerFunction<TableFunctionView>();
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}
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}
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