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// count.cpp
/**
* Copyright (C) 2013 MongoDB 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/ops/count.h"
#include "mongo/db/client.h"
#include "mongo/db/clientcursor.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/query/get_runner.h"
namespace mongo {
static long long applySkipLimit(long long num, const BSONObj& cmd) {
BSONElement s = cmd["skip"];
BSONElement l = cmd["limit"];
if (s.isNumber()) {
num = num - s.numberLong();
if (num < 0) {
num = 0;
}
}
if (l.isNumber()) {
long long limit = l.numberLong();
if (limit < 0) {
limit = -limit;
}
// 0 means no limit.
if (limit < num && limit != 0) {
num = limit;
}
}
return num;
}
long long runCount( const string& ns, const BSONObj &cmd, string &err, int &errCode ) {
// Lock 'ns'.
Client::Context cx(ns);
Collection* collection = cx.db()->getCollection(ns);
if (NULL == collection) {
err = "ns missing";
return -1;
}
BSONObj query = cmd.getObjectField("query");
const std::string hint = cmd.getStringField("hint");
const BSONObj hintObj = hint.empty() ? BSONObj() : BSON("$hint" << hint);
// count of all objects
if (query.isEmpty()) {
return applySkipLimit(collection->numRecords(), cmd);
}
Runner* rawRunner;
long long skip = cmd["skip"].numberLong();
long long limit = cmd["limit"].numberLong();
if (limit < 0) {
limit = -limit;
}
uassertStatusOK(getRunnerCount(collection, query, hintObj, &rawRunner));
auto_ptr<Runner> runner(rawRunner);
try {
const ScopedRunnerRegistration safety(runner.get());
long long count = 0;
Runner::RunnerState state;
while (Runner::RUNNER_ADVANCED == (state = runner->getNext(NULL, NULL))) {
if (skip > 0) {
--skip;
}
else {
++count;
// Fast-path. There's no point in iterating all over the runner if limit
// is set.
if (count >= limit && limit != 0) {
break;
}
}
}
// Emulate old behavior and return the count even if the runner was killed. This
// happens when the underlying collection is dropped.
return count;
}
catch (const DBException &e) {
err = e.toString();
errCode = e.getCode();
}
catch (const std::exception &e) {
err = e.what();
errCode = 0;
}
// Historically we have returned zero in many count assertion cases - see SERVER-2291.
log() << "Count with ns: " << ns << " and query: " << query
<< " failed with exception: " << err << " code: " << errCode
<< endl;
return -2;
}
} // namespace mongo
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