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
160
161
162
163
|
/**
* Copyright (C) 2013 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/>.
*
* 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 GNU Affero General 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.
*/
#pragma once
#include "mongo/db/jsobj.h"
#include "mongo/db/hasher.h"
#include "mongo/db/query/index_bounds_builder.h"
namespace mongo {
/**
* Functions that compute expression index mappings.
*
* TODO: I think we could structure this more generally with respect to planning.
*/
class ExpressionMapping {
public:
static BSONObj hash(const BSONElement& value) {
BSONObjBuilder bob;
bob.append("", BSONElementHasher::hash64(value, BSONElementHasher::DEFAULT_HASH_SEED));
return bob.obj();
}
// TODO: what should we really pass in for indexInfoObj?
static void cover2dsphere(const S2Region& region,
const BSONObj& indexInfoObj,
OrderedIntervalList* oilOut) {
int coarsestIndexedLevel;
BSONElement ce = indexInfoObj["coarsestIndexedLevel"];
if (ce.isNumber()) {
coarsestIndexedLevel = ce.numberInt();
}
else {
coarsestIndexedLevel =
S2::kAvgEdge.GetClosestLevel(100 * 1000.0 / kRadiusOfEarthInMeters);
}
// The min level of our covering is the level whose cells are the closest match to the
// *area* of the region (or the max indexed level, whichever is smaller) The max level
// is 4 sizes larger.
double edgeLen = sqrt(region.GetRectBound().Area());
S2RegionCoverer coverer;
coverer.set_min_level(min(coarsestIndexedLevel,
2 + S2::kAvgEdge.GetClosestLevel(edgeLen)));
coverer.set_max_level(4 + coverer.min_level());
std::vector<S2CellId> cover;
coverer.GetCovering(region, &cover);
// Look at the cells we cover and all cells that are within our covering and finer.
// Anything with our cover as a strict prefix is contained within the cover and should
// be intersection tested.
bool considerCoarser = false;
std::set<std::string> intervalSet;
for (size_t i = 0; i < cover.size(); ++i) {
intervalSet.insert(cover[i].toString());
// If any of our covers could be covered by something in the index, we have
// to look at things coarser.
if (cover[i].level() > coarsestIndexedLevel) {
considerCoarser = true;
}
}
std::set<std::string> exactSet;
if (considerCoarser) {
// Look at the cells that cover us. We want to look at every cell that contains the
// covering we would index on if we were to insert the query geometry. We generate
// the would-index-with-this-covering and find all the cells strictly containing the
// cells in that set, until we hit the coarsest indexed cell. We use equality, not
// a prefix match. Why not prefix? Because we've already looked at everything
// finer or as fine as our initial covering.
//
// Say we have a fine point with cell id 212121, we go up one, get 21212, we don't
// want to look at cells 21212[not-1] because we know they're not going to intersect
// with 212121, but entries inserted with cell value 21212 (no trailing digits) may.
// And we've already looked at points with the cell id 211111 from the regex search
// created above, so we only want things where the value of the last digit is not
// stored (and therefore could be 1).
for (size_t i = 0; i < cover.size(); ++i) {
for (S2CellId id = cover[i].parent(); id.level() >= coarsestIndexedLevel;
id = id.parent()) {
exactSet.insert(id.toString());
}
}
}
// We turned the cell IDs into strings which define point intervals or prefixes of
// strings we want to look for.
std::set<std::string>::iterator exactIt = exactSet.begin();
std::set<std::string>::iterator intervalIt = intervalSet.begin();
while (exactSet.end() != exactIt && intervalSet.end() != intervalIt) {
const std::string& exact = *exactIt;
const std::string& ival = *intervalIt;
if (exact < ival) {
// add exact
oilOut->intervals.push_back(IndexBoundsBuilder::makePointInterval(exact));
exactIt++;
}
else {
std::string end = ival;
end[end.size() - 1]++;
oilOut->intervals.push_back(
IndexBoundsBuilder::makeRangeInterval(ival, end, true, false));
intervalIt++;
}
}
if (exactSet.end() != exactIt) {
verify(intervalSet.end() == intervalIt);
do {
oilOut->intervals.push_back(IndexBoundsBuilder::makePointInterval(*exactIt));
exactIt++;
} while (exactSet.end() != exactIt);
}
else if (intervalSet.end() != intervalIt) {
verify(exactSet.end() == exactIt);
do {
const std::string& ival = *intervalIt;
std::string end = ival;
end[end.size() - 1]++;
oilOut->intervals.push_back(
IndexBoundsBuilder::makeRangeInterval(ival, end, true, false));
intervalIt++;
} while (intervalSet.end() != intervalIt);
}
// Make sure that our intervals don't overlap each other and are ordered correctly.
// This perhaps should only be done in debug mode.
if (!oilOut->isValidFor(1)) {
cout << "check your assumptions! OIL = " << oilOut->toString() << std::endl;
verify(0);
}
}
};
} // namespace mongo
|
