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// distinct.cpp
/**
*
* 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/>.
*/
#include "pch.h"
#include "../commands.h"
#include "../instance.h"
#include "../queryoptimizer.h"
#include "../clientcursor.h"
namespace mongo {
class DistinctCommand : public Command {
public:
DistinctCommand() : Command("distinct") {}
virtual bool slaveOk() const { return true; }
virtual LockType locktype() const { return READ; }
virtual void help( stringstream &help ) const {
help << "{ distinct : 'collection name' , key : 'a.b' , query : {} }";
}
bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
Timer t;
string ns = dbname + '.' + cmdObj.firstElement().valuestr();
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;
long long nscanned = 0; // locations looked at
long long nscannedObjects = 0; // full objects looked at
long long n = 0; // matches
MatchDetails md;
NamespaceDetails * d = nsdetails( ns.c_str() );
if ( ! d ) {
result.appendArray( "values" , BSONObj() );
result.append( "stats" , BSON( "n" << 0 << "nscanned" << 0 << "nscannedObjects" << 0 ) );
return true;
}
shared_ptr<Cursor> cursor;
if ( ! query.isEmpty() ) {
cursor = NamespaceDetailsTransient::getCursor(ns.c_str() , query , BSONObj() );
}
else {
// query is empty, so lets see if we can find an index
// with the key so we don't have to hit the raw data
NamespaceDetails::IndexIterator ii = d->ii();
while ( ii.more() ) {
IndexDetails& idx = ii.next();
if ( d->isMultikey( ii.pos() - 1 ) )
continue;
if ( idx.inKeyPattern( key ) ) {
cursor = bestGuessCursor( ns.c_str() , BSONObj() , idx.keyPattern() );
if( cursor.get() ) break;
}
}
if ( ! cursor.get() )
cursor = NamespaceDetailsTransient::getCursor(ns.c_str() , query , BSONObj() );
}
assert( cursor );
string cursorName = cursor->toString();
auto_ptr<ClientCursor> cc (new ClientCursor(QueryOption_NoCursorTimeout, cursor, ns));
while ( cursor->ok() ) {
nscanned++;
bool loadedObject = false;
if ( ( !cursor->matcher() || cursor->matcher()->matchesCurrent( cursor.get() , &md ) ) &&
!cursor->getsetdup( cursor->currLoc() ) ) {
n++;
BSONObj holder;
BSONElementSet temp;
loadedObject = ! cc->getFieldsDotted( key , temp, holder );
for ( BSONElementSet::iterator i=temp.begin(); i!=temp.end(); ++i ) {
BSONElement e = *i;
if ( values.count( e ) )
continue;
int now = bb.len();
uassert(10044, "distinct too big, 16mb cap", ( now + e.size() + 1024 ) < bufSize );
arr.append( e );
BSONElement x( start + now );
values.insert( x );
}
}
if ( loadedObject || md._loadedObject )
nscannedObjects++;
cursor->advance();
if (!cc->yieldSometimes( ClientCursor::MaybeCovered )) {
cc.release();
break;
}
RARELY killCurrentOp.checkForInterrupt();
}
assert( start == bb.buf() );
result.appendArray( "values" , arr.done() );
{
BSONObjBuilder b;
b.appendNumber( "n" , n );
b.appendNumber( "nscanned" , nscanned );
b.appendNumber( "nscannedObjects" , nscannedObjects );
b.appendNumber( "timems" , t.millis() );
b.append( "cursor" , cursorName );
result.append( "stats" , b.obj() );
}
return true;
}
} distinctCmd;
}
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