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
|
/**
* Copyright (C) 2011 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "mongo/pch.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/value.h"
namespace mongo {
const char DocumentSourceLimit::limitName[] = "$limit";
DocumentSourceLimit::DocumentSourceLimit(const intrusive_ptr<ExpressionContext> &pExpCtx,
long long limit)
: SplittableDocumentSource(pExpCtx)
, limit(limit)
, count(0)
{}
const char *DocumentSourceLimit::getSourceName() const {
return limitName;
}
bool DocumentSourceLimit::coalesce(
const intrusive_ptr<DocumentSource> &pNextSource) {
DocumentSourceLimit *pLimit =
dynamic_cast<DocumentSourceLimit *>(pNextSource.get());
/* if it's not another $skip, we can't coalesce */
if (!pLimit)
return false;
/* we need to limit by the minimum of the two limits */
if (pLimit->limit < limit)
limit = pLimit->limit;
return true;
}
boost::optional<Document> DocumentSourceLimit::getNext() {
pExpCtx->checkForInterrupt();
if (++count > limit) {
pSource->dispose();
return boost::none;
}
return pSource->getNext();
}
Value DocumentSourceLimit::serialize(bool explain) const {
return Value(DOC(getSourceName() << limit));
}
intrusive_ptr<DocumentSourceLimit> DocumentSourceLimit::create(
const intrusive_ptr<ExpressionContext> &pExpCtx,
long long limit) {
uassert(15958, "the limit must be positive",
limit > 0);
return new DocumentSourceLimit(pExpCtx, limit);
}
intrusive_ptr<DocumentSource> DocumentSourceLimit::createFromBson(
BSONElement *pBsonElement,
const intrusive_ptr<ExpressionContext> &pExpCtx) {
uassert(15957, "the limit must be specified as a number",
pBsonElement->isNumber());
long long limit = pBsonElement->numberLong();
return DocumentSourceLimit::create(pExpCtx, limit);
}
}
|
