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/**
* 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.
*/
#include "mongo/db/query/expression_index.h"
#include <iostream>
#include "third_party/s2/s2regioncoverer.h"
#include "mongo/db/geo/geoconstants.h"
#include "mongo/db/geo/hash.h"
#include "mongo/db/geo/r2_region_coverer.h"
#include "mongo/db/hasher.h"
namespace mongo {
using std::set;
BSONObj ExpressionMapping::hash(const BSONElement& value) {
BSONObjBuilder bob;
bob.append("", BSONElementHasher::hash64(value, BSONElementHasher::DEFAULT_HASH_SEED));
return bob.obj();
}
// For debugging only
static std::string toCoveringString(const GeoHashConverter& hashConverter,
const set<GeoHash>& covering) {
string result = "[";
for (set<GeoHash>::const_iterator it = covering.begin(); it != covering.end();
++it) {
if (it != covering.begin()) result += ", ";
const GeoHash& geoHash = *it;
result += hashConverter.unhashToBoxCovering(geoHash).toString();
result += " (" + geoHash.toStringHex1() + ")";
}
return result + "]";
}
void ExpressionMapping::cover2d(const R2Region& region,
const BSONObj& indexInfoObj,
int maxCoveringCells,
OrderedIntervalList* oil) {
GeoHashConverter::Parameters hashParams;
Status paramStatus = GeoHashConverter::parseParameters(indexInfoObj, &hashParams);
verify(paramStatus.isOK()); // We validated the parameters when creating the index
GeoHashConverter hashConverter(hashParams);
R2RegionCoverer coverer(&hashConverter);
coverer.setMaxLevel(hashConverter.getBits());
coverer.setMaxCells(maxCoveringCells);
// TODO: Maybe slightly optimize by returning results in order
vector<GeoHash> unorderedCovering;
coverer.getCovering(region, &unorderedCovering);
set<GeoHash> covering(unorderedCovering.begin(), unorderedCovering.end());
for (set<GeoHash>::const_iterator it = covering.begin(); it != covering.end();
++it) {
const GeoHash& geoHash = *it;
BSONObjBuilder builder;
geoHash.appendHashMin(&builder, "");
geoHash.appendHashMax(&builder, "");
oil->intervals.push_back(IndexBoundsBuilder::makeRangeInterval(builder.obj(),
true,
true));
}
}
// TODO: what should we really pass in for indexInfoObj?
void ExpressionMapping::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.
std::set<string> intervalSet;
std::set<string> exactSet;
for (size_t i = 0; i < cover.size(); ++i) {
S2CellId coveredCell = cover[i];
intervalSet.insert(coveredCell.toString());
// 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).
while (coveredCell.level() > coarsestIndexedLevel) {
// Add the parent cell of the currently covered cell since we aren't at the
// coarsest level yet
// NOTE: Be careful not to generate cells strictly less than the
// coarsestIndexedLevel - this can result in S2 failures when level < 0.
coveredCell = coveredCell.parent();
exactSet.insert(coveredCell.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
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