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Diffstat (limited to 'src/mongo/db/query/query_stats/find_key.h')
| -rw-r--r-- | src/mongo/db/query/query_stats/find_key.h | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/src/mongo/db/query/query_stats/find_key.h b/src/mongo/db/query/query_stats/find_key.h new file mode 100644 index 00000000000..8578a77e573 --- /dev/null +++ b/src/mongo/db/query/query_stats/find_key.h @@ -0,0 +1,152 @@ +/** + * Copyright (C) 2023-present MongoDB, Inc. + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the Server Side Public License, version 1, + * as published by MongoDB, Inc. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * Server Side Public License for more details. + * + * You should have received a copy of the Server Side Public License + * along with this program. If not, see + * <http://www.mongodb.com/licensing/server-side-public-license>. + * + * As a special exception, the copyright holders give permission to link the + * code of portions of this program with the OpenSSL library under certain + * conditions as described in each individual source file and distribute + * linked combinations including the program with the OpenSSL library. You + * must comply with the Server Side Public License in all respects for + * all of the code used other than as permitted herein. If you modify file(s) + * with this exception, you may extend this exception to your version of the + * file(s), but you are not obligated to do so. If you do not wish to do so, + * delete this exception statement from your version. If you delete this + * exception statement from all source files in the program, then also delete + * it in the license file. + */ + +#pragma once + +#include <memory> + +#include "mongo/db/namespace_string.h" +#include "mongo/db/operation_context.h" +#include "mongo/db/query/query_shape/find_cmd_shape.h" +#include "mongo/db/query/query_stats/key.h" + +namespace mongo::query_stats { + +struct FindCmdComponents : public SpecificKeyComponents { + FindCmdComponents(const FindCommandRequest* findCmd) + : _allowPartialResults(findCmd->getAllowPartialResults().value_or(false)), + _noCursorTimeout(findCmd->getNoCursorTimeout().value_or(false)), + _hasField() { + _hasField.batchSize = findCmd->getBatchSize().has_value(); + _hasField.allowPartialResults = findCmd->getAllowPartialResults().has_value(); + _hasField.noCursorTimeout = findCmd->getNoCursorTimeout().has_value(); + } + + std::size_t size() const { + return sizeof(FindCmdComponents); + } + + void HashValue(absl::HashState state) const final { + absl::HashState::combine( + std::move(state), _hasField, _allowPartialResults, _noCursorTimeout); + } + + void appendTo(BSONObjBuilder& bob, const SerializationOptions& opts) const; + + // Avoid using boost::optional here because it creates extra padding at the beginning of the + // struct. Since each QueryStatsEntry can have its own FindKey, it's better to + // minimize the struct's size as much as possible. + + // Preserved literal. + bool _allowPartialResults; + bool _noCursorTimeout; + + // This anonymous struct represents the presence of the member variables as C++ bit fields. + // In doing so, each of these boolean values takes up 1 bit instead of 1 byte. + struct HasField { + HasField() : batchSize(false), allowPartialResults(false), noCursorTimeout(false) {} + bool batchSize : 1; + bool allowPartialResults : 1; + bool noCursorTimeout : 1; + bool operator==(const HasField& other) const { + return batchSize == other.batchSize && + allowPartialResults == other.allowPartialResults && + noCursorTimeout == other.noCursorTimeout; + } + + } _hasField; + + template <typename H> + friend H AbslHashValue(H h, const HasField& hasField) { + return H::combine(std::move(h), + hasField.batchSize, + hasField.noCursorTimeout, + hasField.allowPartialResults); + } +}; + +// This static assert checks to ensure that the struct's size is changed thoughtfully. If adding +// or otherwise changing the members, this assert may be updated with care. +static_assert( + // Expecting two bytes for allowPartialResults and noCursorTimeout, and another + // byte for _hasField. For alignment reasons (alignment is 8 bytes here), this means the trailer + // will bring up the total bytecount to a multiple of 8. + sizeof(FindCmdComponents) <= sizeof(SpecificKeyComponents) + 8, + "Size of FindCmdComponents is too large! " + "Make sure that the struct has been align- and padding-optimized. " + "If the struct's members have changed, this assert may need to be updated with a new " + "value."); + +class FindKey final : public Key { +public: + FindKey(const boost::intrusive_ptr<ExpressionContext>& expCtx, + const ParsedFindCommand& request, + query_shape::CollectionType collectionType = query_shape::CollectionType::kUnknown) + : Key(expCtx->opCtx, + std::make_unique<query_shape::FindCmdShape>(request, expCtx), + request.findCommandRequest->getHint(), + request.findCommandRequest->getReadConcern(), + request.findCommandRequest->getMaxTimeMS().has_value(), + collectionType), + _components(request.findCommandRequest.get()) {} + + // The default implementation of hashing for smart pointers is not a good one for our purposes. + // Here we overload them to actually take the hash of the object, rather than hashing the + // pointer itself. + template <typename H> + friend H AbslHashValue(H h, const std::unique_ptr<const FindKey>& key) { + return H::combine(std::move(h), *key); + } + template <typename H> + friend H AbslHashValue(H h, const std::shared_ptr<const FindKey>& key) { + return H::combine(std::move(h), *key); + } + + const SpecificKeyComponents& specificComponents() const { + return _components; + } + +private: + void appendCommandSpecificComponents(BSONObjBuilder& bob, + const SerializationOptions& opts) const final { + _components.appendTo(bob, opts); + } + + std::unique_ptr<FindCommandRequest> reparse(OperationContext* opCtx) const; + + FindCmdComponents _components; +}; + +// This static assert checks to ensure that the struct's size is changed thoughtfully. If adding +// or otherwise changing the members, this assert may be updated with care. +static_assert(sizeof(FindKey) == sizeof(Key) + sizeof(FindCmdComponents), + "If the class' members have changed, this assert may need to be updated with a new " + "value and the size calcuation will need to be changed."); + +} // namespace mongo::query_stats |
