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/**
* Copyright (C) 2018-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* 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
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* 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 Server Side 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::kWrite
#include "mongo/platform/basic.h"
#include "mongo/db/exec/delete.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/concurrency/write_conflict_exception.h"
#include "mongo/db/curop.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/exec/write_stage_common.h"
#include "mongo/db/op_observer.h"
#include "mongo/db/query/canonical_query.h"
#include "mongo/db/repl/replication_coordinator.h"
#include "mongo/db/service_context.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"
#include "mongo/util/scopeguard.h"
namespace mongo {
using std::unique_ptr;
using std::vector;
using stdx::make_unique;
namespace {
/**
* Returns true if we should throw a WriteConflictException in order to retry the operation in
* the case of a conflict. Returns false if we should skip the document and keep going.
*/
bool shouldRestartDeleteIfNoLongerMatches(const DeleteStageParams& params) {
// When we're doing a findAndModify with a sort, the sort will have a limit of 1, so it will not
// produce any more results even if there is another matching document. Throw a WCE here so that
// these operations get another chance to find a matching document. The findAndModify command
// should automatically retry if it gets a WCE.
return params.returnDeleted && !params.sort.isEmpty();
};
} // namespace
// static
const char* DeleteStage::kStageType = "DELETE";
DeleteStage::DeleteStage(OperationContext* opCtx,
const DeleteStageParams& params,
WorkingSet* ws,
Collection* collection,
PlanStage* child)
: PlanStage(kStageType, opCtx),
_params(params),
_ws(ws),
_collection(collection),
_idRetrying(WorkingSet::INVALID_ID),
_idReturning(WorkingSet::INVALID_ID) {
_children.emplace_back(child);
}
bool DeleteStage::isEOF() {
if (!_collection) {
return true;
}
if (!_params.isMulti && _specificStats.docsDeleted > 0) {
return true;
}
return _idRetrying == WorkingSet::INVALID_ID && _idReturning == WorkingSet::INVALID_ID &&
child()->isEOF();
}
PlanStage::StageState DeleteStage::doWork(WorkingSetID* out) {
if (isEOF()) {
return PlanStage::IS_EOF;
}
invariant(_collection); // If isEOF() returns false, we must have a collection.
// It is possible that after a delete was executed, a WriteConflictException occurred
// and prevented us from returning ADVANCED with the old version of the document.
if (_idReturning != WorkingSet::INVALID_ID) {
// We should only get here if we were trying to return something before.
invariant(_params.returnDeleted);
WorkingSetMember* member = _ws->get(_idReturning);
invariant(member->getState() == WorkingSetMember::OWNED_OBJ);
*out = _idReturning;
_idReturning = WorkingSet::INVALID_ID;
return PlanStage::ADVANCED;
}
// Either retry the last WSM we worked on or get a new one from our child.
WorkingSetID id;
if (_idRetrying != WorkingSet::INVALID_ID) {
id = _idRetrying;
_idRetrying = WorkingSet::INVALID_ID;
} else {
auto status = child()->work(&id);
switch (status) {
case PlanStage::ADVANCED:
break;
case PlanStage::FAILURE:
case PlanStage::DEAD:
// The stage which produces a failure is responsible for allocating a working set
// member with error details.
invariant(WorkingSet::INVALID_ID != id);
*out = id;
return status;
case PlanStage::NEED_TIME:
return status;
case PlanStage::NEED_YIELD:
*out = id;
return status;
case PlanStage::IS_EOF:
return status;
default:
MONGO_UNREACHABLE;
}
}
// We advanced, or are retrying, and id is set to the WSM to work on.
WorkingSetMember* member = _ws->get(id);
// We want to free this member when we return, unless we need to retry deleting or returning it.
ScopeGuard memberFreer = MakeGuard(&WorkingSet::free, _ws, id);
invariant(member->hasRecordId());
RecordId recordId = member->recordId;
// Deletes can't have projections. This means that covering analysis will always add
// a fetch. We should always get fetched data, and never just key data.
invariant(member->hasObj());
// Ensure the document still exists and matches the predicate.
bool docStillMatches;
try {
docStillMatches = write_stage_common::ensureStillMatches(
_collection, getOpCtx(), _ws, id, _params.canonicalQuery);
} catch (const WriteConflictException&) {
// There was a problem trying to detect if the document still exists, so retry.
memberFreer.Dismiss();
return prepareToRetryWSM(id, out);
}
if (!docStillMatches) {
// Either the document has already been deleted, or it has been updated such that it no
// longer matches the predicate.
if (shouldRestartDeleteIfNoLongerMatches(_params)) {
throw WriteConflictException();
}
return PlanStage::NEED_TIME;
}
// Ensure that the BSONObj underlying the WorkingSetMember is owned because saveState() is
// allowed to free the memory.
if (_params.returnDeleted) {
// Save a copy of the document that is about to get deleted, but keep it in the RID_AND_OBJ
// state in case we need to retry deleting it.
BSONObj deletedDoc = member->obj.value();
member->obj.setValue(deletedDoc.getOwned());
}
// TODO: Do we want to buffer docs and delete them in a group rather than saving/restoring state
// repeatedly?
WorkingSetCommon::prepareForSnapshotChange(_ws);
try {
child()->saveState();
} catch (const WriteConflictException&) {
std::terminate();
}
// Do the write, unless this is an explain.
if (!_params.isExplain) {
try {
WriteUnitOfWork wunit(getOpCtx());
_collection->deleteDocument(getOpCtx(),
_params.stmtId,
recordId,
_params.opDebug,
_params.fromMigrate,
false,
_params.returnDeleted ? Collection::StoreDeletedDoc::On
: Collection::StoreDeletedDoc::Off);
wunit.commit();
} catch (const WriteConflictException&) {
memberFreer.Dismiss(); // Keep this member around so we can retry deleting it.
return prepareToRetryWSM(id, out);
}
}
++_specificStats.docsDeleted;
if (_params.returnDeleted) {
// After deleting the document, the RecordId associated with this member is invalid.
// Remove the 'recordId' from the WorkingSetMember before returning it.
member->recordId = RecordId();
member->transitionToOwnedObj();
}
// As restoreState may restore (recreate) cursors, cursors are tied to the transaction in which
// they are created, and a WriteUnitOfWork is a transaction, make sure to restore the state
// outside of the WriteUnitOfWork.
try {
child()->restoreState();
} catch (const WriteConflictException&) {
// Note we don't need to retry anything in this case since the delete already was committed.
// However, we still need to return the deleted document (if it was requested).
if (_params.returnDeleted) {
// member->obj should refer to the deleted document.
invariant(member->getState() == WorkingSetMember::OWNED_OBJ);
_idReturning = id;
// Keep this member around so that we can return it on the next work() call.
memberFreer.Dismiss();
}
*out = WorkingSet::INVALID_ID;
return NEED_YIELD;
}
if (_params.returnDeleted) {
// member->obj should refer to the deleted document.
invariant(member->getState() == WorkingSetMember::OWNED_OBJ);
memberFreer.Dismiss(); // Keep this member around so we can return it.
*out = id;
return PlanStage::ADVANCED;
}
return PlanStage::NEED_TIME;
}
void DeleteStage::doRestoreState() {
invariant(_collection);
const NamespaceString& ns(_collection->ns());
uassert(ErrorCodes::PrimarySteppedDown,
str::stream() << "Demoted from primary while removing from " << ns.ns(),
!getOpCtx()->writesAreReplicated() ||
repl::ReplicationCoordinator::get(getOpCtx())->canAcceptWritesFor(getOpCtx(), ns));
}
unique_ptr<PlanStageStats> DeleteStage::getStats() {
_commonStats.isEOF = isEOF();
unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_DELETE);
ret->specific = make_unique<DeleteStats>(_specificStats);
ret->children.emplace_back(child()->getStats());
return ret;
}
const SpecificStats* DeleteStage::getSpecificStats() const {
return &_specificStats;
}
// static
long long DeleteStage::getNumDeleted(const PlanExecutor& exec) {
invariant(exec.getRootStage()->isEOF());
invariant(exec.getRootStage()->stageType() == STAGE_DELETE);
DeleteStage* deleteStage = static_cast<DeleteStage*>(exec.getRootStage());
const DeleteStats* deleteStats =
static_cast<const DeleteStats*>(deleteStage->getSpecificStats());
return deleteStats->docsDeleted;
}
PlanStage::StageState DeleteStage::prepareToRetryWSM(WorkingSetID idToRetry, WorkingSetID* out) {
_idRetrying = idToRetry;
*out = WorkingSet::INVALID_ID;
return NEED_YIELD;
}
} // namespace mongo
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