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// distinct.cpp
/**
* Copyright (C) 2012-2014 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 <string>
#include <vector>
#include "mongo/db/auth/action_set.h"
#include "mongo/db/auth/action_type.h"
#include "mongo/db/auth/privilege.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/clientcursor.h"
#include "mongo/db/commands.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/instance.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/query/explain.h"
#include "mongo/db/query/get_executor.h"
#include "mongo/db/query/query_planner_common.h"
#include "mongo/util/timer.h"
namespace mongo {
using std::auto_ptr;
using std::string;
using std::stringstream;
class DistinctCommand : public Command {
public:
DistinctCommand() : Command("distinct") {}
virtual bool slaveOk() const { return false; }
virtual bool slaveOverrideOk() const { return true; }
virtual bool isWriteCommandForConfigServer() const { return false; }
virtual void addRequiredPrivileges(const std::string& dbname,
const BSONObj& cmdObj,
std::vector<Privilege>* out) {
ActionSet actions;
actions.addAction(ActionType::find);
out->push_back(Privilege(parseResourcePattern(dbname, cmdObj), actions));
}
virtual void help( stringstream &help ) const {
help << "{ distinct : 'collection name' , key : 'a.b' , query : {} }";
}
bool run(OperationContext* txn,
const string& dbname,
BSONObj& cmdObj,
int,
string& errmsg,
BSONObjBuilder& result) {
Timer t;
// ensure that the key is a string
uassert(18510,
mongoutils::str::stream() << "The first argument to the distinct command " <<
"must be a string but was a " << typeName(cmdObj["key"].type()),
cmdObj["key"].type() == mongo::String);
// ensure that the where clause is a document
if( cmdObj["query"].isNull() == false && cmdObj["query"].eoo() == false ){
uassert(18511,
mongoutils::str::stream() << "The query for the distinct command must be a " <<
"document but was a " << typeName(cmdObj["query"].type()),
cmdObj["query"].type() == mongo::Object);
}
string key = cmdObj["key"].valuestrsafe();
BSONObj keyPattern = BSON( key << 1 );
BSONObj query = getQuery( cmdObj );
int bufSize = BSONObjMaxUserSize - 4096;
BufBuilder bb( bufSize );
char * start = bb.buf();
BSONArrayBuilder arr( bb );
BSONElementSet values;
const string ns = parseNs(dbname, cmdObj);
AutoGetCollectionForRead ctx(txn, ns);
Collection* collection = ctx.getCollection();
if (!collection) {
result.appendArray( "values" , BSONObj() );
result.append("stats", BSON("n" << 0 <<
"nscanned" << 0 <<
"nscannedObjects" << 0));
return true;
}
PlanExecutor* rawExec;
Status status = getExecutorDistinct(txn,
collection,
query,
key,
PlanExecutor::YIELD_AUTO,
&rawExec);
if (!status.isOK()) {
uasserted(17216, mongoutils::str::stream() << "Can't get executor for query "
<< query << ": " << status.toString());
return 0;
}
auto_ptr<PlanExecutor> exec(rawExec);
BSONObj obj;
PlanExecutor::ExecState state;
while (PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
// Distinct expands arrays.
//
// If our query is covered, each value of the key should be in the index key and
// available to us without this. If a collection scan is providing the data, we may
// have to expand an array.
BSONElementSet elts;
obj.getFieldsDotted(key, elts);
for (BSONElementSet::iterator it = elts.begin(); it != elts.end(); ++it) {
BSONElement elt = *it;
if (values.count(elt)) { continue; }
int currentBufPos = bb.len();
uassert(17217, "distinct too big, 16mb cap",
(currentBufPos + elt.size() + 1024) < bufSize);
arr.append(elt);
BSONElement x(start + currentBufPos);
values.insert(x);
}
}
// Get summary information about the plan.
PlanSummaryStats stats;
Explain::getSummaryStats(exec.get(), &stats);
verify( start == bb.buf() );
result.appendArray( "values" , arr.done() );
{
BSONObjBuilder b;
b.appendNumber( "n" , stats.nReturned );
b.appendNumber( "nscanned" , stats.totalKeysExamined );
b.appendNumber( "nscannedObjects" , stats.totalDocsExamined );
b.appendNumber( "timems" , t.millis() );
b.append( "planSummary" , Explain::getPlanSummary(exec.get()) );
result.append( "stats" , b.obj() );
}
return true;
}
} distinctCmd;
} // namespace mongo
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