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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::kQuery
#include "mongo/db/exec/projection.h"
#include "mongo/db/exec/plan_stage.h"
#include "mongo/db/exec/scoped_timer.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/jsobj.h"
#include "mongo/db/matcher/expression.h"
#include "mongo/db/record_id.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"
#include "mongo/util/mongoutils/str.h"
namespace mongo {
using std::endl;
using std::unique_ptr;
using std::vector;
using stdx::make_unique;
static const char* kIdField = "_id";
// static
const char* ProjectionStage::kStageType = "PROJECTION";
ProjectionStage::ProjectionStage(OperationContext* opCtx,
const ProjectionStageParams& params,
WorkingSet* ws,
PlanStage* child)
: PlanStage(kStageType, opCtx), _ws(ws), _projImpl(params.projImpl) {
_children.emplace_back(child);
_projObj = params.projObj;
if (ProjectionStageParams::NO_FAST_PATH == _projImpl) {
_exec.reset(
new ProjectionExec(opCtx, params.projObj, params.fullExpression, params.collator));
} else {
// We shouldn't need the full expression if we're fast-pathing.
invariant(NULL == params.fullExpression);
// Sanity-check the input.
invariant(_projObj.isOwned());
invariant(!_projObj.isEmpty());
// Figure out what fields are in the projection.
getSimpleInclusionFields(_projObj, &_includedFields);
// If we're pulling data out of one index we can pre-compute the indices of the fields
// in the key that we pull data from and avoid looking up the field name each time.
if (ProjectionStageParams::COVERED_ONE_INDEX == params.projImpl) {
// Sanity-check.
_coveredKeyObj = params.coveredKeyObj;
invariant(_coveredKeyObj.isOwned());
BSONObjIterator kpIt(_coveredKeyObj);
while (kpIt.more()) {
BSONElement elt = kpIt.next();
auto fieldIt = _includedFields.find(elt.fieldNameStringData());
if (_includedFields.end() == fieldIt) {
// Push an unused value on the back to keep _includeKey and _keyFieldNames
// in sync.
_keyFieldNames.push_back(StringData());
_includeKey.push_back(false);
} else {
// If we are including this key field store its field name.
_keyFieldNames.push_back(fieldIt->first);
_includeKey.push_back(true);
}
}
} else {
invariant(ProjectionStageParams::SIMPLE_DOC == params.projImpl);
}
}
}
// static
void ProjectionStage::getSimpleInclusionFields(const BSONObj& projObj, FieldSet* includedFields) {
// The _id is included by default.
bool includeId = true;
// Figure out what fields are in the projection. TODO: we can get this from the
// ParsedProjection...modify that to have this type instead of a vector.
BSONObjIterator projObjIt(projObj);
while (projObjIt.more()) {
BSONElement elt = projObjIt.next();
// Must deal with the _id case separately as there is an implicit _id: 1 in the
// projection.
if (mongoutils::str::equals(elt.fieldName(), kIdField) && !elt.trueValue()) {
includeId = false;
continue;
}
(*includedFields)[elt.fieldNameStringData()] = true;
}
if (includeId) {
(*includedFields)[kIdField] = true;
}
}
// static
void ProjectionStage::transformSimpleInclusion(const BSONObj& in,
const FieldSet& includedFields,
BSONObjBuilder& bob) {
// Look at every field in the source document and see if we're including it.
BSONObjIterator inputIt(in);
while (inputIt.more()) {
BSONElement elt = inputIt.next();
auto fieldIt = includedFields.find(elt.fieldNameStringData());
if (includedFields.end() != fieldIt) {
// If so, add it to the builder.
bob.append(elt);
}
}
}
Status ProjectionStage::transform(WorkingSetMember* member) {
// The default no-fast-path case.
if (ProjectionStageParams::NO_FAST_PATH == _projImpl) {
return _exec->transform(member);
}
BSONObjBuilder bob;
// SIMPLE_DOC implies that we expect an object so it's kind of redundant.
if ((ProjectionStageParams::SIMPLE_DOC == _projImpl) || member->hasObj()) {
// If we got here because of SIMPLE_DOC the planner shouldn't have messed up.
invariant(member->hasObj());
// Apply the SIMPLE_DOC projection.
transformSimpleInclusion(member->obj.value(), _includedFields, bob);
} else {
invariant(ProjectionStageParams::COVERED_ONE_INDEX == _projImpl);
// We're pulling data out of the key.
invariant(1 == member->keyData.size());
size_t keyIndex = 0;
// Look at every key element...
BSONObjIterator keyIterator(member->keyData[0].keyData);
while (keyIterator.more()) {
BSONElement elt = keyIterator.next();
// If we're supposed to include it...
if (_includeKey[keyIndex]) {
// Do so.
bob.appendAs(elt, _keyFieldNames[keyIndex]);
}
++keyIndex;
}
}
member->keyData.clear();
member->recordId = RecordId();
member->obj = Snapshotted<BSONObj>(SnapshotId(), bob.obj());
member->transitionToOwnedObj();
return Status::OK();
}
bool ProjectionStage::isEOF() {
return child()->isEOF();
}
PlanStage::StageState ProjectionStage::doWork(WorkingSetID* out) {
WorkingSetID id = WorkingSet::INVALID_ID;
StageState status = child()->work(&id);
// Note that we don't do the normal if isEOF() return EOF thing here. Our child might be a
// tailable cursor and isEOF() would be true even if it had more data...
if (PlanStage::ADVANCED == status) {
WorkingSetMember* member = _ws->get(id);
// Punt to our specific projection impl.
Status projStatus = transform(member);
if (!projStatus.isOK()) {
warning() << "Couldn't execute projection, status = " << redact(projStatus);
*out = WorkingSetCommon::allocateStatusMember(_ws, projStatus);
return PlanStage::FAILURE;
}
*out = id;
} else if (PlanStage::FAILURE == status || PlanStage::DEAD == status) {
// The stage which produces a failure is responsible for allocating a working set member
// with error details.
invariant(WorkingSet::INVALID_ID != id);
*out = id;
} else if (PlanStage::NEED_YIELD == status) {
*out = id;
}
return status;
}
unique_ptr<PlanStageStats> ProjectionStage::getStats() {
_commonStats.isEOF = isEOF();
unique_ptr<PlanStageStats> ret = make_unique<PlanStageStats>(_commonStats, STAGE_PROJECTION);
unique_ptr<ProjectionStats> projStats = make_unique<ProjectionStats>(_specificStats);
projStats->projObj = _projObj;
ret->specific = std::move(projStats);
ret->children.emplace_back(child()->getStats());
return ret;
}
const SpecificStats* ProjectionStage::getSpecificStats() const {
return &_specificStats;
}
} // namespace mongo
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