1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
|
/**
* 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;
// Failpoint for making find hang.
MONGO_FAIL_POINT_DECLARE(waitInFindBeforeMakingBatch);
// Failpoint for making getMore not wait for an awaitdata cursor. Allows us to avoid waiting during
// tests.
MONGO_FAIL_POINT_DECLARE(disableAwaitDataForGetMoreCmd);
// Enabling this fail point will cause getMores to busy wait after pinning the cursor
// but before we have started building the batch, until the fail point is disabled.
MONGO_FAIL_POINT_DECLARE(waitAfterPinningCursorBeforeGetMoreBatch);
// Enabling this fail point will cause getMores to busy wait after setting up the plan executor and
// before beginning the batch.
MONGO_FAIL_POINT_DECLARE(waitWithPinnedCursorDuringGetMoreBatch);
// Enabling this failpoint will cause getMores to wait just before it unpins its cursor after it
// has completed building the current batch.
MONGO_FAIL_POINT_DECLARE(waitBeforeUnpinningOrDeletingCursorAfterGetMoreBatch);
/**
* 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
|
