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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/bson/bsonobj.h"
#include "mongo/db/operation_context.h"
#include "mongo/util/fail_point_service.h"
namespace mongo {
/**
* The state associated with tailable cursors.
*/
struct AwaitDataState {
/**
* The deadline for how long we wait on the tail of capped collection before returning IS_EOF.
*/
Date_t waitForInsertsDeadline;
/**
* If true, when no results are available from a plan, then instead of returning immediately,
* the system should wait up to the length of the operation deadline for data to be inserted
* which causes results to become available.
*/
bool shouldWaitForInserts;
};
extern const OperationContext::Decoration<AwaitDataState> awaitDataState;
class BSONObj;
class QueryRequest;
// Enabling this fail point will cause the getMore command to busy wait after pinning the cursor,
// until the fail point is disabled.
MONGO_FP_FORWARD_DECLARE(keepCursorPinnedDuringGetMore);
// Failpoint for making getMore not wait for an awaitdata cursor. Allows us to avoid waiting during
// tests.
MONGO_FP_FORWARD_DECLARE(disableAwaitDataForGetMoreCmd);
/**
* Suite of find/getMore related functions used in both the mongod and mongos query paths.
*/
class FindCommon {
public:
// The maximum amount of user data to return to a client in a single batch.
//
// This max may be exceeded by epsilon for output documents that approach the maximum user
// document size. That is, if we must return a BSONObjMaxUserSize document, then the total
// response size will be BSONObjMaxUserSize plus the amount of size required for the message
// header and the cursor response "envelope". (The envolope contains namespace and cursor id
// info.)
static const int kMaxBytesToReturnToClientAtOnce = BSONObjMaxUserSize;
// The initial size of the query response buffer.
static const int kInitReplyBufferSize = 32768;
/**
* Returns true if the batchSize for the initial find has been satisfied.
*
* If 'qr' does not have a batchSize, the default batchSize is respected.
*/
static bool enoughForFirstBatch(const QueryRequest& qr, long long numDocs);
/**
* Returns true if the batchSize for the getMore has been satisfied.
*
* An 'effectiveBatchSize' value of zero is interpreted as the absence of a batchSize, in which
* case this method returns false.
*/
static bool enoughForGetMore(long long effectiveBatchSize, long long numDocs) {
return effectiveBatchSize && numDocs >= effectiveBatchSize;
}
/**
* Given the number of docs ('numDocs') and bytes ('bytesBuffered') currently buffered as a
* response to a cursor-generating command, returns true if there are enough remaining bytes in
* our budget to fit 'nextDoc'.
*/
static bool haveSpaceForNext(const BSONObj& nextDoc, long long numDocs, int bytesBuffered);
/**
* Transforms the raw sort spec into one suitable for use as the ordering specification in
* BSONObj::woCompare().
*
* In particular, eliminates text score meta-sort from 'sortSpec'.
*
* The input must be validated (each BSON element must be either a number or text score
* meta-sort specification).
*/
static BSONObj transformSortSpec(const BSONObj& sortSpec);
};
} // namespace mongo
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