// parallel_collection_scan.cpp
/**
* Copyright (C) 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 .
*
* 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/platform/basic.h"
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/commands.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/exec/multi_iterator.h"
#include "mongo/db/query/cursor_responses.h"
#include "mongo/util/touch_pages.h"
namespace mongo {
using std::unique_ptr;
using std::string;
class ParallelCollectionScanCmd : public Command {
public:
struct ExtentInfo {
ExtentInfo( RecordId dl, size_t s )
: diskLoc(dl), size(s) {
}
RecordId diskLoc;
size_t size;
};
// ------------------------------------------------
ParallelCollectionScanCmd() : Command( "parallelCollectionScan" ){}
virtual bool isWriteCommandForConfigServer() const { return false; }
virtual bool slaveOk() const { return true; }
virtual Status checkAuthForCommand(ClientBasic* client,
const std::string& dbname,
const BSONObj& cmdObj) {
ActionSet actions;
actions.addAction(ActionType::find);
Privilege p(parseResourcePattern(dbname, cmdObj), actions);
if ( AuthorizationSession::get(client)->isAuthorizedForPrivilege(p) )
return Status::OK();
return Status(ErrorCodes::Unauthorized, "Unauthorized");
}
virtual bool run(OperationContext* txn,
const string& dbname,
BSONObj& cmdObj,
int options,
string& errmsg,
BSONObjBuilder& result) {
NamespaceString ns( dbname, cmdObj[name].String() );
AutoGetCollectionForRead ctx(txn, ns.ns());
Collection* collection = ctx.getCollection();
if ( !collection )
return appendCommandStatus( result,
Status( ErrorCodes::NamespaceNotFound,
str::stream() <<
"ns does not exist: " << ns.ns() ) );
size_t numCursors = static_cast( cmdObj["numCursors"].numberInt() );
if ( numCursors == 0 || numCursors > 10000 )
return appendCommandStatus( result,
Status( ErrorCodes::BadValue,
str::stream() <<
"numCursors has to be between 1 and 10000" <<
" was: " << numCursors ) );
auto iterators = collection->getManyCursors(txn);
if (iterators.size() < numCursors) {
numCursors = iterators.size();
}
OwnedPointerVector execs;
for ( size_t i = 0; i < numCursors; i++ ) {
WorkingSet* ws = new WorkingSet();
MultiIteratorStage* mis = new MultiIteratorStage(txn, ws, collection);
PlanExecutor* rawExec;
// Takes ownership of 'ws' and 'mis'.
Status execStatus = PlanExecutor::make(txn, ws, mis, collection,
PlanExecutor::YIELD_AUTO, &rawExec);
invariant(execStatus.isOK());
unique_ptr curExec(rawExec);
// The PlanExecutor was registered on construction due to the YIELD_AUTO policy.
// We have to deregister it, as it will be registered with ClientCursor.
curExec->deregisterExec();
// Need to save state while yielding locks between now and getMore().
curExec->saveState();
execs.push_back(curExec.release());
}
// transfer iterators to executors using a round-robin distribution.
// TODO consider using a common work queue once invalidation issues go away.
for (size_t i = 0; i < iterators.size(); i++) {
PlanExecutor* theExec = execs[i % execs.size()];
MultiIteratorStage* mis = static_cast(theExec->getRootStage());
// This wasn't called above as they weren't assigned yet
iterators[i]->savePositioned();
mis->addIterator(std::move(iterators[i]));
}
{
BSONArrayBuilder bucketsBuilder;
for (size_t i = 0; i < execs.size(); i++) {
// transfer ownership of an executor to the ClientCursor (which manages its own
// lifetime).
ClientCursor* cc = new ClientCursor( collection->getCursorManager(),
execs.releaseAt(i),
ns.ns() );
BSONObjBuilder threadResult;
appendCursorResponseObject( cc->cursorid(),
ns.ns(),
BSONArray(),
&threadResult );
threadResult.appendBool( "ok", 1 );
bucketsBuilder.append( threadResult.obj() );
}
result.appendArray( "cursors", bucketsBuilder.obj() );
}
return true;
}
} parallelCollectionScanCmd;
}