summaryrefslogtreecommitdiff
path: root/src/mongo/db/field_ref_set.cpp
blob: cbfcee236d3528d074dfe31c6f6080b1da11b7ee (plain)
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
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
/**
 *    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/field_ref_set.h"

#include "mongo/util/assert_util.h"
#include "mongo/util/str.h"

namespace mongo {

using std::vector;
using std::string;

namespace {

// For legacy purposes, we must handle empty fieldnames, which FieldRef clearly
// prohibits. It is preferrable to have FieldRef keep that constraint and relax it here
// -- stricly in update code. The rationale is that, if we want to ban data with no
// field names, we must allow that data to be updated.
StringData safeFirstPart(const FieldRef* fieldRef) {
    if (fieldRef->numParts() == 0) {
        return StringData();
    } else {
        return fieldRef->getPart(0);
    }
}
}

bool FieldRefSet::FieldRefPtrLessThan::operator()(const FieldRef* l, const FieldRef* r) const {
    return *l < *r;
}

FieldRefSet::FieldRefSet() {}

FieldRefSet::FieldRefSet(const vector<FieldRef*>& paths) {
    fillFrom(paths);
}

bool FieldRefSet::findConflicts(const FieldRef* toCheck, FieldRefSet* conflicts) const {
    bool foundConflict = false;

    // If the set is empty, there is no work to do.
    if (_fieldSet.empty())
        return foundConflict;

    StringData prefixStr = safeFirstPart(toCheck);
    FieldRef prefixField(prefixStr);

    FieldSet::iterator it = _fieldSet.lower_bound(&prefixField);
    // Now, iterate over all the present fields in the set that have the same prefix.

    while (it != _fieldSet.end() && safeFirstPart(*it) == prefixStr) {
        size_t common = (*it)->commonPrefixSize(*toCheck);
        if ((*it)->numParts() == common || toCheck->numParts() == common) {
            if (!conflicts)
                return true;

            conflicts->_fieldSet.insert(*it);
            foundConflict = true;
        }
        ++it;
    }

    return foundConflict;
}

void FieldRefSet::keepShortest(const FieldRef* toInsert) {
    const FieldRef* conflict;
    if (!insert(toInsert, &conflict) && (toInsert->numParts() < (conflict->numParts()))) {
        _fieldSet.erase(conflict);
        keepShortest(toInsert);
    }
}

void FieldRefSet::fillFrom(const std::vector<FieldRef*>& fields) {
    dassert(_fieldSet.empty());
    _fieldSet.insert(fields.begin(), fields.end());
}

bool FieldRefSet::insert(const FieldRef* toInsert, const FieldRef** conflict) {
    // We can determine if two fields conflict by checking their common prefix.
    //
    // If each field is exactly of the size of the common prefix, this means the fields are
    // the same. If one of the fields is greater than the common prefix and the other
    // isn't, the latter is a prefix of the former. And vice-versa.
    //
    // Example:
    //
    // inserted >      |    a          a.c
    // exiting  v      |   (0)        (+1)
    // ----------------|------------------------
    //      a (0)      |  equal      prefix <
    //      a.b (+1)   | prefix ^      *
    //
    // * Disjoint sub-trees

    // At each insertion, we only need to bother checking the fields in the set that have
    // at least some common prefix with the 'toInsert' field.
    StringData prefixStr = safeFirstPart(toInsert);
    FieldRef prefixField(prefixStr);
    FieldSet::iterator it = _fieldSet.lower_bound(&prefixField);

    // Now, iterate over all the present fields in the set that have the same prefix.
    while (it != _fieldSet.end() && safeFirstPart(*it) == prefixStr) {
        size_t common = (*it)->commonPrefixSize(*toInsert);
        if ((*it)->numParts() == common || toInsert->numParts() == common) {
            *conflict = *it;
            return false;
        }
        ++it;
    }

    _fieldSet.insert(it, toInsert);
    *conflict = NULL;
    return true;
}

const std::string FieldRefSet::toString() const {
    str::stream ss;
    ss << "{";
    const auto last = _fieldSet.rbegin();
    for (auto path : _fieldSet) {
        ss << path->dottedField();
        if (path != *last)
            ss << ", ";
    }
    ss << "}";
    return ss;
}

}  // namespace mongo