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/**
* Copyright (C) 2018-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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/query/find_common.h"
#include "mongo/bson/bsonobj.h"
#include "mongo/db/curop.h"
#include "mongo/db/curop_failpoint_helpers.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/query/query_request_helper.h"
#include "mongo/logv2/log.h"
#include "mongo/util/assert_util.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kQuery
namespace mongo {
MONGO_FAIL_POINT_DEFINE(waitInFindBeforeMakingBatch);
MONGO_FAIL_POINT_DEFINE(disableAwaitDataForGetMoreCmd);
MONGO_FAIL_POINT_DEFINE(waitAfterPinningCursorBeforeGetMoreBatch);
MONGO_FAIL_POINT_DEFINE(waitWithPinnedCursorDuringGetMoreBatch);
MONGO_FAIL_POINT_DEFINE(waitBeforeUnpinningOrDeletingCursorAfterGetMoreBatch);
MONGO_FAIL_POINT_DEFINE(failGetMoreAfterCursorCheckout);
const OperationContext::Decoration<AwaitDataState> awaitDataState =
OperationContext::declareDecoration<AwaitDataState>();
const size_t FindCommon::kMaxBytesToReturnToClientAtOnce = BSONObjMaxUserSize;
const size_t FindCommon::kTailableGetMoreReplyBufferSize = BSONObjMaxUserSize / 2 - 1024;
const size_t FindCommon::kMinDocSizeForGetMorePreAllocation = 1024;
const size_t FindCommon::kInitReplyBufferSize = 32768;
bool FindCommon::enoughForFirstBatch(const FindCommandRequest& findCommand, long long numDocs) {
auto batchSize = findCommand.getBatchSize();
if (!batchSize) {
// We enforce a default batch size for the initial find if no batch size is specified.
return numDocs >= query_request_helper::kDefaultBatchSize;
}
return numDocs >= batchSize.value();
}
bool FindCommon::haveSpaceForNext(const BSONObj& nextDoc, long long numDocs, size_t bytesBuffered) {
invariant(numDocs >= 0);
if (!numDocs) {
// Allow the first output document to exceed the limit to ensure we can always make
// progress.
return true;
}
return (bytesBuffered + nextDoc.objsize()) <= kMaxBytesToReturnToClientAtOnce;
}
void FindCommon::waitInFindBeforeMakingBatch(OperationContext* opCtx, const CanonicalQuery& cq) {
auto whileWaitingFunc = [&, hasLogged = false]() mutable {
if (!std::exchange(hasLogged, true)) {
LOGV2(20908,
"Waiting in find before making batch for query",
"query"_attr = redact(cq.toStringShort()));
}
};
CurOpFailpointHelpers::waitWhileFailPointEnabled(&mongo::waitInFindBeforeMakingBatch,
opCtx,
"waitInFindBeforeMakingBatch",
std::move(whileWaitingFunc),
cq.nss());
}
std::size_t FindCommon::getBytesToReserveForGetMoreReply(bool isTailable,
size_t firstResultSize,
size_t batchSize) {
#ifdef _WIN32
// SERVER-22100: In Windows DEBUG builds, the CRT heap debugging overhead, in
// conjunction with the additional memory pressure introduced by reply buffer
// pre-allocation, causes the concurrency suite to run extremely slowly. As a workaround
// we do not pre-allocate in Windows DEBUG builds.
if (kDebugBuild)
return 0;
#endif
// A tailable cursor may often return 0 or very few results. Allocate a small initial
// buffer. This buffer should be big-enough to accomodate for at least one document.
if (isTailable) {
return std::max(firstResultSize, kTailableGetMoreReplyBufferSize);
}
// A getMore with batchSize is likely to return limited results. Allocate a medium
// initial buffer based on an estimate of document sizes and the given batch size.
if (batchSize > 0) {
size_t estmtObjSize = std::max(kMinDocSizeForGetMorePreAllocation, firstResultSize);
return std::min(estmtObjSize * batchSize, kMaxBytesToReturnToClientAtOnce);
}
// Otherwise, reserve enough buffer to fit a full batch of results. The allocator will
// assign a little more than the requested amount to avoid reallocation when we add
// command metadata to the reply.
return kMaxBytesToReturnToClientAtOnce;
}
} // namespace mongo
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