/**
* Copyright (C) 2013-2014 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.
*/
#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kQuery
#include "mongo/db/exec/collection_scan.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/exec/collection_scan_common.h"
#include "mongo/db/exec/filter.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/storage/record_fetcher.h"
#include "mongo/util/fail_point_service.h"
#include "mongo/util/log.h"
#include "mongo/db/client.h" // XXX-ERH
namespace mongo {
// static
const char* CollectionScan::kStageType = "COLLSCAN";
CollectionScan::CollectionScan(OperationContext* txn,
const CollectionScanParams& params,
WorkingSet* workingSet,
const MatchExpression* filter)
: _txn(txn),
_workingSet(workingSet),
_filter(filter),
_params(params),
_isDead(false),
_wsidForFetch(_workingSet->allocate()),
_commonStats(kStageType) {
// Explain reports the direction of the collection scan.
_specificStats.direction = params.direction;
// We pre-allocate a WSM and use it to pass up fetch requests. This should never be used
// for anything other than passing up NEED_FETCH. We use the loc and owned obj state, but
// the loc isn't really pointing at any obj. The obj field of the WSM should never be used.
WorkingSetMember* member = _workingSet->get(_wsidForFetch);
member->state = WorkingSetMember::LOC_AND_OWNED_OBJ;
}
PlanStage::StageState CollectionScan::work(WorkingSetID* out) {
++_commonStats.works;
// Adds the amount of time taken by work() to executionTimeMillis.
ScopedTimer timer(&_commonStats.executionTimeMillis);
if (_isDead) { return PlanStage::DEAD; }
// Do some init if we haven't already.
if (NULL == _iter) {
if ( _params.collection == NULL ) {
_isDead = true;
return PlanStage::DEAD;
}
if (_lastSeenLoc.isNull()) {
_iter.reset( _params.collection->getIterator( _txn,
_params.start,
_params.direction ) );
}
else {
invariant(_params.tailable);
_iter.reset( _params.collection->getIterator( _txn,
_lastSeenLoc,
_params.direction ) );
// Advance _iter past where we were last time. If it returns something else, mark us
// as dead since we want to signal an error rather than silently dropping data from
// the stream. This is related to the _lastSeenLock handling in invalidate.
if (_iter->getNext() != _lastSeenLoc) {
_isDead = true;
return PlanStage::DEAD;
}
}
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
// Should we try getNext() on the underlying _iter?
if (isEOF())
return PlanStage::IS_EOF;
const RecordId curr = _iter->curr();
if (curr.isNull()) {
// We just hit EOF
if (_params.tailable)
_iter.reset(); // pick up where we left off on the next call to work()
return PlanStage::IS_EOF;
}
_lastSeenLoc = curr;
// See if the record we're about to access is in memory. If not, pass a fetch request up.
// Note that curr() does not touch the record (on MMAPv1 which is the only place we use
// NEED_FETCH) so we are able to yield before touching the record, as long as we do so
// before calling getNext().
{
std::auto_ptr fetcher(
_params.collection->documentNeedsFetch(_txn, curr));
if (NULL != fetcher.get()) {
WorkingSetMember* member = _workingSet->get(_wsidForFetch);
member->loc = curr;
// Pass the RecordFetcher off to the WSM.
member->setFetcher(fetcher.release());
*out = _wsidForFetch;
_commonStats.needFetch++;
return NEED_FETCH;
}
}
WorkingSetID id = _workingSet->allocate();
WorkingSetMember* member = _workingSet->get(id);
member->loc = curr;
member->obj = _iter->dataFor(member->loc).releaseToBson();
member->state = WorkingSetMember::LOC_AND_UNOWNED_OBJ;
// Advance the iterator.
invariant(_iter->getNext() == curr);
return returnIfMatches(member, id, out);
}
PlanStage::StageState CollectionScan::returnIfMatches(WorkingSetMember* member,
WorkingSetID memberID,
WorkingSetID* out) {
++_specificStats.docsTested;
if (Filter::passes(member, _filter)) {
*out = memberID;
++_commonStats.advanced;
return PlanStage::ADVANCED;
}
else {
_workingSet->free(memberID);
++_commonStats.needTime;
return PlanStage::NEED_TIME;
}
}
bool CollectionScan::isEOF() {
if ((0 != _params.maxScan) && (_specificStats.docsTested >= _params.maxScan)) {
return true;
}
if (_isDead) { return true; }
if (NULL == _iter) { return false; }
if (_params.tailable) { return false; } // tailable cursors can return data later.
return _iter->isEOF();
}
void CollectionScan::invalidate(OperationContext* txn,
const RecordId& dl,
InvalidationType type) {
++_commonStats.invalidates;
// We don't care about mutations since we apply any filters to the result when we (possibly)
// return it.
if (INVALIDATION_DELETION != type) {
return;
}
// If we're here, 'dl' is being deleted.
// Deletions can harm the underlying RecordIterator so we must pass them down.
if (NULL != _iter) {
_iter->invalidate(dl);
}
if (_params.tailable && dl == _lastSeenLoc) {
// This means that deletes have caught up to the reader. We want to error in this case
// so readers don't miss potentially important data.
_isDead = true;
}
}
void CollectionScan::saveState() {
_txn = NULL;
++_commonStats.yields;
if (NULL != _iter) {
_iter->saveState();
}
}
void CollectionScan::restoreState(OperationContext* opCtx) {
invariant(_txn == NULL);
_txn = opCtx;
++_commonStats.unyields;
if (NULL != _iter) {
if (!_iter->restoreState(opCtx)) {
warning() << "Collection dropped or state deleted during yield of CollectionScan: "
<< opCtx->getNS();
_isDead = true;
}
}
}
vector CollectionScan::getChildren() const {
vector empty;
return empty;
}
PlanStageStats* CollectionScan::getStats() {
_commonStats.isEOF = isEOF();
// Add a BSON representation of the filter to the stats tree, if there is one.
if (NULL != _filter) {
BSONObjBuilder bob;
_filter->toBSON(&bob);
_commonStats.filter = bob.obj();
}
auto_ptr ret(new PlanStageStats(_commonStats, STAGE_COLLSCAN));
ret->specific.reset(new CollectionScanStats(_specificStats));
return ret.release();
}
const CommonStats* CollectionScan::getCommonStats() {
return &_commonStats;
}
const SpecificStats* CollectionScan::getSpecificStats() {
return &_specificStats;
}
} // namespace mongo