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* Copyright (C) 2012 10gen Inc.
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License, version 3,
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* as published by the Free Software Foundation.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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#include "mongo/db/geo/s2common.h"
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const double S2IndexingParams::kRadiusOfEarthInMeters = (6378.1 * 1000);
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static string myitoa(int d) {
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void S2SearchUtil::setCoverLimitsBasedOnArea(double area, S2RegionCoverer *coverer,
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int coarsestIndexedLevel) {
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coverer->set_min_level(min(coarsestIndexedLevel, 2 + S2::kAvgEdge.GetClosestLevel(area)));
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coverer->set_max_level(4 + coverer->min_level());
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BSONObj S2SearchUtil::coverAsBSON(const vector<S2CellId> &cover, const string& field,
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const int coarsestIndexedLevel) {
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BSONObjBuilder queryBuilder;
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BSONObjBuilder inBuilder(queryBuilder.subobjStart(field));
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// To have an array where elements of that array are regexes, we have to do this.
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BSONObjBuilder inArrayBuilder(inBuilder.subarrayStart("$in"));
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// Sadly we must keep track of this ourselves. Oh, BSONObjBuilder, you rascal!
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bool considerCoarser = false;
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// Look at the cells we cover and all cells that are within our covering and
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// finer. Anything with our cover as a strict prefix is contained within the cover and
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// should be intersection tested.
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for (size_t i = 0; i < cover.size(); ++i) {
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// First argument is position in the array as a string.
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// Third argument is options to regex.
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inArrayBuilder.appendRegex(myitoa(arrayPos++), "^" + cover[i].toString(), "");
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// If any of our covers could be covered by something in the index, we have
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// to look at things coarser.
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considerCoarser = considerCoarser || (cover[i].level() > coarsestIndexedLevel);
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if (considerCoarser) {
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// Look at the cells that cover us. We want to look at every cell that
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// contains the covering we would index on if we were to insert the
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// query geometry. We generate the would-index-with-this-covering and
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// find all the cells strictly containing the cells in that set, until we hit the
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// coarsest indexed cell. We use $in, not a prefix match. Why not prefix? Because
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// we've already looked at everything finer or as fine as our initial covering.
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// Say we have a fine point with cell id 212121, we go up one, get 21212, we don't
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// want to look at cells 21212[not-1] because we know they're not going to intersect
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// with 212121, but entries inserted with cell value 21212 (no trailing digits) may.
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// And we've already looked at points with the cell id 211111 from the regex search
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// created above, so we only want things where the value of the last digit is not
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// stored (and therefore could be 1).
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unordered_set<S2CellId> parents;
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for (size_t i = 0; i < cover.size(); ++i) {
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for (S2CellId id = cover[i].parent(); id.level() >= coarsestIndexedLevel;
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for (unordered_set<S2CellId>::const_iterator it = parents.begin(); it != parents.end(); ++it) {
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inArrayBuilder.append(myitoa(arrayPos++), it->toString());
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inArrayBuilder.done();
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return queryBuilder.obj();