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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::kCommand
#include "mongo/platform/basic.h"
#include "mongo/db/commands/run_aggregate.h"
#include <boost/optional.hpp>
#include <vector>
#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/curop.h"
#include "mongo/db/cursor_manager.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/exec/change_stream_proxy.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/pipeline/accumulator.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/document_source_exchange.h"
#include "mongo/db/pipeline/document_source_geo_near.h"
#include "mongo/db/pipeline/expression.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/pipeline/lite_parsed_pipeline.h"
#include "mongo/db/pipeline/mongo_process_interface.h"
#include "mongo/db/pipeline/pipeline.h"
#include "mongo/db/pipeline/pipeline_d.h"
#include "mongo/db/query/collation/collator_factory_interface.h"
#include "mongo/db/query/cursor_response.h"
#include "mongo/db/query/find_common.h"
#include "mongo/db/query/get_executor.h"
#include "mongo/db/query/plan_summary_stats.h"
#include "mongo/db/query/query_planner_common.h"
#include "mongo/db/read_concern.h"
#include "mongo/db/repl/oplog.h"
#include "mongo/db/repl/read_concern_args.h"
#include "mongo/db/repl/speculative_majority_read_info.h"
#include "mongo/db/s/sharding_state.h"
#include "mongo/db/service_context.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/db/transaction_participant.h"
#include "mongo/db/views/view.h"
#include "mongo/db/views/view_catalog.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"
#include "mongo/util/scopeguard.h"
#include "mongo/util/string_map.h"
namespace mongo {
using boost::intrusive_ptr;
using std::endl;
using std::shared_ptr;
using std::string;
using std::stringstream;
using std::unique_ptr;
using stdx::make_unique;
namespace {
/**
* Returns true if this PlanExecutor is for a Pipeline.
*/
bool isPipelineExecutor(const PlanExecutor* exec) {
invariant(exec);
auto rootStage = exec->getRootStage();
return rootStage->stageType() == StageType::STAGE_PIPELINE_PROXY ||
rootStage->stageType() == StageType::STAGE_CHANGE_STREAM_PROXY;
}
/**
* If a pipeline is empty (assuming that a $cursor stage hasn't been created yet), it could mean
* that we were able to absorb all pipeline stages and pull them into a single PlanExecutor. So,
* instead of creating a whole pipeline to do nothing more than forward the results of its cursor
* document source, we can optimize away the entire pipeline and answer the request using the query
* engine only. This function checks if such optimization is possible.
*/
bool canOptimizeAwayPipeline(const Pipeline* pipeline,
const PlanExecutor* exec,
const AggregationRequest& request,
bool hasGeoNearStage,
bool hasChangeStreamStage) {
return pipeline && exec && !hasGeoNearStage && !hasChangeStreamStage &&
pipeline->getSources().empty() &&
// For exchange we will create a number of pipelines consisting of a single
// DocumentSourceExchange stage, so cannot not optimize it away.
!request.getExchangeSpec() &&
!QueryPlannerCommon::hasNode(exec->getCanonicalQuery()->root(), MatchExpression::TEXT);
}
/**
* Returns true if we need to keep a ClientCursor saved for this pipeline (for future getMore
* requests). Otherwise, returns false. The passed 'nsForCursor' is only used to determine the
* namespace used in the returned cursor, which will be registered with the global cursor manager,
* and thus will be different from that in 'request'.
*/
bool handleCursorCommand(OperationContext* opCtx,
const NamespaceString& nsForCursor,
std::vector<ClientCursor*> cursors,
const AggregationRequest& request,
rpc::ReplyBuilderInterface* result) {
invariant(!cursors.empty());
long long batchSize = request.getBatchSize();
if (cursors.size() > 1) {
uassert(
ErrorCodes::BadValue, "the exchange initial batch size must be zero", batchSize == 0);
BSONArrayBuilder cursorsBuilder;
for (size_t idx = 0; idx < cursors.size(); ++idx) {
invariant(cursors[idx]);
BSONObjBuilder cursorResult;
appendCursorResponseObject(
cursors[idx]->cursorid(), nsForCursor.ns(), BSONArray(), &cursorResult);
cursorResult.appendBool("ok", 1);
cursorsBuilder.append(cursorResult.obj());
// If a time limit was set on the pipeline, remaining time is "rolled over" to the
// cursor (for use by future getmore ops).
cursors[idx]->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
// Cursor needs to be in a saved state while we yield locks for getmore. State
// will be restored in getMore().
cursors[idx]->getExecutor()->saveState();
cursors[idx]->getExecutor()->detachFromOperationContext();
}
auto bodyBuilder = result->getBodyBuilder();
bodyBuilder.appendArray("cursors", cursorsBuilder.obj());
return true;
}
CursorResponseBuilder::Options options;
options.isInitialResponse = true;
CursorResponseBuilder responseBuilder(result, options);
auto curOp = CurOp::get(opCtx);
auto cursor = cursors[0];
invariant(cursor);
auto exec = cursor->getExecutor();
invariant(exec);
BSONObj next;
bool stashedResult = false;
for (int objCount = 0; objCount < batchSize; objCount++) {
// The initial getNext() on a PipelineProxyStage may be very expensive so we don't
// do it when batchSize is 0 since that indicates a desire for a fast return.
PlanExecutor::ExecState state;
try {
state = exec->getNext(&next, nullptr);
} catch (const ExceptionFor<ErrorCodes::CloseChangeStream>&) {
// This exception is thrown when a $changeStream stage encounters an event
// that invalidates the cursor. We should close the cursor and return without
// error.
cursor = nullptr;
exec = nullptr;
break;
}
if (state == PlanExecutor::IS_EOF) {
if (!cursor->isTailable()) {
// make it an obvious error to use cursor or executor after this point
cursor = nullptr;
exec = nullptr;
}
break;
}
if (PlanExecutor::ADVANCED != state) {
uassertStatusOK(WorkingSetCommon::getMemberObjectStatus(next).withContext(
"PlanExecutor error during aggregation"));
}
// If adding this object will cause us to exceed the message size limit, then we stash it
// for later.
if (!FindCommon::haveSpaceForNext(next, objCount, responseBuilder.bytesUsed())) {
exec->enqueue(next);
stashedResult = true;
break;
}
// TODO SERVER-38539: We need to set both the latestOplogTimestamp and the PBRT until the
// former is removed in a future release.
responseBuilder.setLatestOplogTimestamp(exec->getLatestOplogTimestamp());
responseBuilder.setPostBatchResumeToken(exec->getPostBatchResumeToken());
responseBuilder.append(next);
}
if (cursor) {
invariant(cursor->getExecutor() == exec);
// For empty batches, or in the case where the final result was added to the batch rather
// than being stashed, we update the PBRT to ensure that it is the most recent available.
if (!stashedResult) {
// TODO SERVER-38539: We need to set both the latestOplogTimestamp and the PBRT until
// the former is removed in a future release.
responseBuilder.setLatestOplogTimestamp(exec->getLatestOplogTimestamp());
responseBuilder.setPostBatchResumeToken(exec->getPostBatchResumeToken());
}
// If a time limit was set on the pipeline, remaining time is "rolled over" to the
// cursor (for use by future getmore ops).
cursor->setLeftoverMaxTimeMicros(opCtx->getRemainingMaxTimeMicros());
curOp->debug().cursorid = cursor->cursorid();
// Cursor needs to be in a saved state while we yield locks for getmore. State
// will be restored in getMore().
exec->saveState();
exec->detachFromOperationContext();
} else {
curOp->debug().cursorExhausted = true;
}
const CursorId cursorId = cursor ? cursor->cursorid() : 0LL;
responseBuilder.done(cursorId, nsForCursor.ns());
return static_cast<bool>(cursor);
}
StatusWith<StringMap<ExpressionContext::ResolvedNamespace>> resolveInvolvedNamespaces(
OperationContext* opCtx, const AggregationRequest& request) {
const LiteParsedPipeline liteParsedPipeline(request);
const auto& pipelineInvolvedNamespaces = liteParsedPipeline.getInvolvedNamespaces();
// If there are no involved namespaces, return before attempting to take any locks. This is
// important for collectionless aggregations, which may be expected to run without locking.
if (pipelineInvolvedNamespaces.empty()) {
return {StringMap<ExpressionContext::ResolvedNamespace>()};
}
// We intentionally do not drop and reacquire our DB lock after resolving the view definition in
// order to prevent the definition for any view namespaces we've already resolved from changing.
// This is necessary to prevent a cycle from being formed among the view definitions cached in
// 'resolvedNamespaces' because we won't re-resolve a view namespace we've already encountered.
AutoGetDb autoDb(opCtx, request.getNamespaceString().db(), MODE_IS);
Database* const db = autoDb.getDb();
ViewCatalog* viewCatalog = db ? ViewCatalog::get(db) : nullptr;
std::deque<NamespaceString> involvedNamespacesQueue(pipelineInvolvedNamespaces.begin(),
pipelineInvolvedNamespaces.end());
StringMap<ExpressionContext::ResolvedNamespace> resolvedNamespaces;
while (!involvedNamespacesQueue.empty()) {
auto involvedNs = std::move(involvedNamespacesQueue.front());
involvedNamespacesQueue.pop_front();
if (resolvedNamespaces.find(involvedNs.coll()) != resolvedNamespaces.end()) {
continue;
}
if (involvedNs.db() != request.getNamespaceString().db()) {
// If the involved namespace is not in the same database as the aggregation, it must be
// from a $out to a collection in a different database. Since we cannot write to views,
// simply assume that the namespace is a collection.
resolvedNamespaces[involvedNs.coll()] = {involvedNs, std::vector<BSONObj>{}};
} else if (!db || db->getCollection(opCtx, involvedNs)) {
// If the aggregation database exists and 'involvedNs' refers to a collection namespace,
// then we resolve it as an empty pipeline in order to read directly from the underlying
// collection. If the database doesn't exist, then we still resolve it as an empty
// pipeline because 'involvedNs' doesn't refer to a view namespace in our consistent
// snapshot of the view catalog.
resolvedNamespaces[involvedNs.coll()] = {involvedNs, std::vector<BSONObj>{}};
} else if (viewCatalog->lookup(opCtx, involvedNs.ns())) {
// If 'involvedNs' refers to a view namespace, then we resolve its definition.
auto resolvedView = viewCatalog->resolveView(opCtx, involvedNs);
if (!resolvedView.isOK()) {
return {ErrorCodes::FailedToParse,
str::stream() << "Failed to resolve view '" << involvedNs.ns() << "': "
<< resolvedView.getStatus().toString()};
}
resolvedNamespaces[involvedNs.coll()] = {resolvedView.getValue().getNamespace(),
resolvedView.getValue().getPipeline()};
// We parse the pipeline corresponding to the resolved view in case we must resolve
// other view namespaces that are also involved.
LiteParsedPipeline resolvedViewLitePipeline(
{resolvedView.getValue().getNamespace(), resolvedView.getValue().getPipeline()});
const auto& resolvedViewInvolvedNamespaces =
resolvedViewLitePipeline.getInvolvedNamespaces();
involvedNamespacesQueue.insert(involvedNamespacesQueue.end(),
resolvedViewInvolvedNamespaces.begin(),
resolvedViewInvolvedNamespaces.end());
} else {
// 'involvedNs' is neither a view nor a collection, so resolve it as an empty pipeline
// to treat it as reading from a non-existent collection.
resolvedNamespaces[involvedNs.coll()] = {involvedNs, std::vector<BSONObj>{}};
}
}
return resolvedNamespaces;
}
/**
* Returns Status::OK if each view namespace in 'pipeline' has a default collator equivalent to
* 'collator'. Otherwise, returns ErrorCodes::OptionNotSupportedOnView.
*/
Status collatorCompatibleWithPipeline(OperationContext* opCtx,
Database* db,
const CollatorInterface* collator,
const LiteParsedPipeline& liteParsedPipeline) {
if (!db) {
return Status::OK();
}
for (auto&& potentialViewNs : liteParsedPipeline.getInvolvedNamespaces()) {
if (db->getCollection(opCtx, potentialViewNs)) {
continue;
}
auto view = ViewCatalog::get(db)->lookup(opCtx, potentialViewNs.ns());
if (!view) {
continue;
}
if (!CollatorInterface::collatorsMatch(view->defaultCollator(), collator)) {
return {ErrorCodes::OptionNotSupportedOnView,
str::stream() << "Cannot override default collation of view "
<< potentialViewNs.ns()};
}
}
return Status::OK();
}
/**
* Resolves the collator to either the user-specified collation or, if none was specified, to the
* collection-default collation.
*/
std::unique_ptr<CollatorInterface> resolveCollator(OperationContext* opCtx,
const AggregationRequest& request,
const Collection* collection) {
if (!request.getCollation().isEmpty()) {
return uassertStatusOK(CollatorFactoryInterface::get(opCtx->getServiceContext())
->makeFromBSON(request.getCollation()));
}
return (collection && collection->getDefaultCollator()
? collection->getDefaultCollator()->clone()
: nullptr);
}
boost::intrusive_ptr<ExpressionContext> makeExpressionContext(
OperationContext* opCtx,
const AggregationRequest& request,
std::unique_ptr<CollatorInterface> collator,
boost::optional<UUID> uuid) {
boost::intrusive_ptr<ExpressionContext> expCtx =
new ExpressionContext(opCtx,
request,
std::move(collator),
MongoProcessInterface::create(opCtx),
uassertStatusOK(resolveInvolvedNamespaces(opCtx, request)),
uuid);
expCtx->tempDir = storageGlobalParams.dbpath + "/_tmp";
auto txnParticipant = TransactionParticipant::get(opCtx);
expCtx->inMultiDocumentTransaction =
txnParticipant && txnParticipant.inMultiDocumentTransaction();
return expCtx;
}
/**
* Upconverts the read concern for a change stream aggregation, if necesssary.
*
* If there is no given read concern level on the given object, upgrades the level to 'majority' and
* waits for read concern. If a read concern level is already specified on the given read concern
* object, this method does nothing.
*/
void _adjustChangeStreamReadConcern(OperationContext* opCtx) {
repl::ReadConcernArgs& readConcernArgs = repl::ReadConcernArgs::get(opCtx);
// There is already a read concern level set. Do nothing.
if (readConcernArgs.hasLevel()) {
return;
}
// We upconvert an empty read concern to 'majority'.
{
// We must obtain the client lock to set the ReadConcernArgs on the operation
// context as it may be concurrently read by CurrentOp.
stdx::lock_guard<Client> lk(*opCtx->getClient());
readConcernArgs = repl::ReadConcernArgs(repl::ReadConcernLevel::kMajorityReadConcern);
// Change streams are allowed to use the speculative majority read mechanism, if
// the storage engine doesn't support majority reads directly.
if (!serverGlobalParams.enableMajorityReadConcern) {
readConcernArgs.setMajorityReadMechanism(
repl::ReadConcernArgs::MajorityReadMechanism::kSpeculative);
}
}
// Wait for read concern again since we changed the original read concern.
uassertStatusOK(
waitForReadConcern(opCtx, readConcernArgs, true, PrepareConflictBehavior::kIgnore));
}
/**
* If the aggregation 'request' contains an exchange specification, create a new pipeline for each
* consumer and put it into the resulting vector. Otherwise, return the original 'pipeline' as a
* single vector element.
*/
std::vector<std::unique_ptr<Pipeline, PipelineDeleter>> createExchangePipelinesIfNeeded(
OperationContext* opCtx,
boost::intrusive_ptr<ExpressionContext> expCtx,
const AggregationRequest& request,
std::unique_ptr<Pipeline, PipelineDeleter> pipeline,
boost::optional<UUID> uuid) {
std::vector<std::unique_ptr<Pipeline, PipelineDeleter>> pipelines;
if (request.getExchangeSpec() && !expCtx->explain) {
boost::intrusive_ptr<Exchange> exchange =
new Exchange(request.getExchangeSpec().get(), std::move(pipeline));
for (size_t idx = 0; idx < exchange->getConsumers(); ++idx) {
// For every new pipeline we have create a new ExpressionContext as the context
// cannot be shared between threads. There is no synchronization for pieces of
// the execution machinery above the Exchange, so nothing above the Exchange can be
// shared between different exchange-producer cursors.
expCtx = makeExpressionContext(opCtx,
request,
expCtx->getCollator() ? expCtx->getCollator()->clone()
: nullptr,
uuid);
// Create a new pipeline for the consumer consisting of a single
// DocumentSourceExchange.
boost::intrusive_ptr<DocumentSource> consumer = new DocumentSourceExchange(
expCtx, exchange, idx, expCtx->mongoProcessInterface->getResourceYielder());
pipelines.emplace_back(uassertStatusOK(Pipeline::create({consumer}, expCtx)));
}
} else {
pipelines.emplace_back(std::move(pipeline));
}
return pipelines;
}
/**
* Create a PlanExecutor to execute the given 'pipeline'.
*/
std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> createOuterPipelineProxyExecutor(
OperationContext* opCtx,
const NamespaceString& nss,
std::unique_ptr<Pipeline, PipelineDeleter> pipeline,
bool hasChangeStream) {
// Transfer ownership of the Pipeline to the PipelineProxyStage.
auto ws = make_unique<WorkingSet>();
auto proxy = hasChangeStream
? make_unique<ChangeStreamProxyStage>(opCtx, std::move(pipeline), ws.get())
: make_unique<PipelineProxyStage>(opCtx, std::move(pipeline), ws.get());
// This PlanExecutor will simply forward requests to the Pipeline, so does not need
// to yield or to be registered with any collection's CursorManager to receive
// invalidations. The Pipeline may contain PlanExecutors which *are* yielding
// PlanExecutors and which *are* registered with their respective collection's
// CursorManager
return uassertStatusOK(
PlanExecutor::make(opCtx, std::move(ws), std::move(proxy), nss, PlanExecutor::NO_YIELD));
}
} // namespace
Status runAggregate(OperationContext* opCtx,
const NamespaceString& origNss,
const AggregationRequest& request,
const BSONObj& cmdObj,
const PrivilegeVector& privileges,
rpc::ReplyBuilderInterface* result) {
// For operations on views, this will be the underlying namespace.
NamespaceString nss = request.getNamespaceString();
// The collation to use for this aggregation. boost::optional to distinguish between the case
// where the collation has not yet been resolved, and where it has been resolved to nullptr.
boost::optional<std::unique_ptr<CollatorInterface>> collatorToUse;
// The UUID of the collection for the execution namespace of this aggregation.
boost::optional<UUID> uuid;
// If emplaced, AutoGetCollectionForReadCommand will throw if the sharding version for this
// connection is out of date. If the namespace is a view, the lock will be released before
// re-running the expanded aggregation.
boost::optional<AutoGetCollectionForReadCommand> ctx;
std::vector<unique_ptr<PlanExecutor, PlanExecutor::Deleter>> execs;
boost::intrusive_ptr<ExpressionContext> expCtx;
auto curOp = CurOp::get(opCtx);
{
const LiteParsedPipeline liteParsedPipeline(request);
try {
// Check whether the parsed pipeline supports the given read concern.
liteParsedPipeline.assertSupportsReadConcern(
opCtx, request.getExplain(), serverGlobalParams.enableMajorityReadConcern);
} catch (const DBException& ex) {
auto txnParticipant = TransactionParticipant::get(opCtx);
// If we are in a multi-document transaction, we intercept the 'readConcern'
// assertion in order to provide a more descriptive error message and code.
if (txnParticipant && txnParticipant.inMultiDocumentTransaction()) {
return {ErrorCodes::OperationNotSupportedInTransaction,
ex.toStatus("Operation not permitted in transaction").reason()};
}
return ex.toStatus();
}
const auto& pipelineInvolvedNamespaces = liteParsedPipeline.getInvolvedNamespaces();
// If this is a collectionless aggregation, we won't create 'ctx' but will still need an
// AutoStatsTracker to record CurOp and Top entries.
boost::optional<AutoStatsTracker> statsTracker;
// If this is a change stream, perform special checks and change the execution namespace.
if (liteParsedPipeline.hasChangeStream()) {
// Replace the execution namespace with that of the oplog.
nss = NamespaceString::kRsOplogNamespace;
// Upgrade and wait for read concern if necessary.
_adjustChangeStreamReadConcern(opCtx);
// AutoGetCollectionForReadCommand will raise an error if 'origNss' is a view. We do not
// need to check this if we are opening a stream on an entire db or across the cluster.
if (!origNss.isCollectionlessAggregateNS()) {
AutoGetCollectionForReadCommand origNssCtx(opCtx, origNss);
}
// If the user specified an explicit collation, adopt it; otherwise, use the simple
// collation. We do not inherit the collection's default collation or UUID, since
// the stream may be resuming from a point before the current UUID existed.
collatorToUse.emplace(resolveCollator(opCtx, request, nullptr));
// Obtain collection locks on the execution namespace; that is, the oplog.
ctx.emplace(opCtx, nss, AutoGetCollection::ViewMode::kViewsForbidden);
} else if (nss.isCollectionlessAggregateNS() && pipelineInvolvedNamespaces.empty()) {
// If this is a collectionless agg with no foreign namespaces, don't acquire any locks.
statsTracker.emplace(opCtx,
nss,
Top::LockType::NotLocked,
AutoStatsTracker::LogMode::kUpdateTopAndCurop,
0);
collatorToUse.emplace(resolveCollator(opCtx, request, nullptr));
} else {
// This is a regular aggregation. Lock the collection or view.
ctx.emplace(opCtx, nss, AutoGetCollection::ViewMode::kViewsPermitted);
collatorToUse.emplace(resolveCollator(opCtx, request, ctx->getCollection()));
uuid = ctx->getCollection() ? ctx->getCollection()->uuid() : boost::none;
}
Collection* collection = ctx ? ctx->getCollection() : nullptr;
// If this is a view, resolve it by finding the underlying collection and stitching view
// pipelines and this request's pipeline together. We then release our locks before
// recursively calling runAggregate(), which will re-acquire locks on the underlying
// collection. (The lock must be released because recursively acquiring locks on the
// database will prohibit yielding.)
if (ctx && ctx->getView() && !liteParsedPipeline.startsWithCollStats()) {
invariant(nss != NamespaceString::kRsOplogNamespace);
invariant(!nss.isCollectionlessAggregateNS());
// Check that the default collation of 'view' is compatible with the operation's
// collation. The check is skipped if the request did not specify a collation.
if (!request.getCollation().isEmpty()) {
invariant(collatorToUse); // Should already be resolved at this point.
if (!CollatorInterface::collatorsMatch(ctx->getView()->defaultCollator(),
collatorToUse->get())) {
return {ErrorCodes::OptionNotSupportedOnView,
"Cannot override a view's default collation"};
}
}
auto resolvedView =
uassertStatusOK(ViewCatalog::get(ctx->getDb())->resolveView(opCtx, nss));
uassert(std::move(resolvedView),
"On sharded systems, resolved views must be executed by mongos",
!ShardingState::get(opCtx)->enabled());
// With the view & collation resolved, we can relinquish locks.
ctx.reset();
// Parse the resolved view into a new aggregation request.
auto newRequest = resolvedView.asExpandedViewAggregation(request);
auto newCmd = newRequest.serializeToCommandObj().toBson();
auto status = runAggregate(opCtx, origNss, newRequest, newCmd, privileges, result);
{
// Set the namespace of the curop back to the view namespace so ctx records
// stats on this view namespace on destruction.
stdx::lock_guard<Client> lk(*opCtx->getClient());
curOp->setNS_inlock(nss.ns());
}
return status;
}
invariant(collatorToUse);
expCtx = makeExpressionContext(opCtx, request, std::move(*collatorToUse), uuid);
auto pipeline = uassertStatusOK(Pipeline::parse(request.getPipeline(), expCtx));
// Check that the view's collation matches the collation of any views involved in the
// pipeline.
if (!pipelineInvolvedNamespaces.empty()) {
invariant(ctx);
auto pipelineCollationStatus = collatorCompatibleWithPipeline(
opCtx, ctx->getDb(), expCtx->getCollator(), liteParsedPipeline);
if (!pipelineCollationStatus.isOK()) {
return pipelineCollationStatus;
}
}
pipeline->optimizePipeline();
// Check if the pipeline has a $geoNear stage, as it will be ripped away during the build
// query executor phase below (to be replaced with a $geoNearCursorStage later during the
// executor attach phase).
auto hasGeoNearStage = !pipeline->getSources().empty() &&
dynamic_cast<DocumentSourceGeoNear*>(pipeline->peekFront());
// Prepare a PlanExecutor to provide input into the pipeline, if needed.
std::pair<PipelineD::AttachExecutorCallback,
std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>>
attachExecutorCallback;
if (liteParsedPipeline.hasChangeStream()) {
// If we are using a change stream, the cursor stage should have a simple collation,
// regardless of what the user's collation was.
std::unique_ptr<CollatorInterface> collatorForCursor = nullptr;
auto collatorStash = expCtx->temporarilyChangeCollator(std::move(collatorForCursor));
attachExecutorCallback =
PipelineD::buildInnerQueryExecutor(collection, nss, &request, pipeline.get());
} else {
attachExecutorCallback =
PipelineD::buildInnerQueryExecutor(collection, nss, &request, pipeline.get());
}
if (canOptimizeAwayPipeline(pipeline.get(),
attachExecutorCallback.second.get(),
request,
hasGeoNearStage,
liteParsedPipeline.hasChangeStream())) {
// This pipeline is currently empty, but once completed it will have only one source,
// which is a DocumentSourceCursor. Instead of creating a whole pipeline to do nothing
// more than forward the results of its cursor document source, we can use the
// PlanExecutor by itself. The resulting cursor will look like what the client would
// have gotten from find command.
execs.emplace_back(std::move(attachExecutorCallback.second));
} else {
// Complete creation of the initial $cursor stage, if needed.
PipelineD::attachInnerQueryExecutorToPipeline(collection,
attachExecutorCallback.first,
std::move(attachExecutorCallback.second),
pipeline.get());
// Optimize again, since there may be additional optimizations that can be done after
// adding the initial cursor stage.
pipeline->optimizePipeline();
auto pipelines =
createExchangePipelinesIfNeeded(opCtx, expCtx, request, std::move(pipeline), uuid);
for (auto&& pipelineIt : pipelines) {
execs.emplace_back(createOuterPipelineProxyExecutor(
opCtx, nss, std::move(pipelineIt), liteParsedPipeline.hasChangeStream()));
}
// With the pipelines created, we can relinquish locks as they will manage the locks
// internally further on. We still need to keep the lock for an optimized away pipeline
// though, as we will be changing its lock policy to 'kLockExternally' (see details
// below), and in order to execute the initial getNext() call in 'handleCursorCommand',
// we need to hold the collection lock.
ctx.reset();
}
{
auto planSummary = Explain::getPlanSummary(execs[0].get());
stdx::lock_guard<Client> lk(*opCtx->getClient());
curOp->setPlanSummary_inlock(std::move(planSummary));
}
}
// Having released the collection lock, we can now create a cursor that returns results from the
// pipeline. This cursor owns no collection state, and thus we register it with the global
// cursor manager. The global cursor manager does not deliver invalidations or kill
// notifications; the underlying PlanExecutor(s) used by the pipeline will be receiving
// invalidations and kill notifications themselves, not the cursor we create here.
std::vector<ClientCursorPin> pins;
std::vector<ClientCursor*> cursors;
auto cursorFreer = makeGuard([&] {
for (auto& p : pins) {
p.deleteUnderlying();
}
});
for (auto&& exec : execs) {
// PlanExecutors for pipelines always have a 'kLocksInternally' policy. If this executor is
// not for a pipeline, though, that means the pipeline was optimized away and the
// PlanExecutor will answer the query using the query engine only. Without the
// DocumentSourceCursor to do its locking, an executor needs a 'kLockExternally' policy.
auto lockPolicy = isPipelineExecutor(exec.get())
? ClientCursorParams::LockPolicy::kLocksInternally
: ClientCursorParams::LockPolicy::kLockExternally;
ClientCursorParams cursorParams(
std::move(exec),
origNss,
AuthorizationSession::get(opCtx->getClient())->getAuthenticatedUserNames(),
repl::ReadConcernArgs::get(opCtx),
cmdObj,
lockPolicy,
privileges);
if (expCtx->tailableMode == TailableModeEnum::kTailable) {
cursorParams.setTailable(true);
} else if (expCtx->tailableMode == TailableModeEnum::kTailableAndAwaitData) {
cursorParams.setTailable(true);
cursorParams.setAwaitData(true);
}
auto pin = CursorManager::get(opCtx)->registerCursor(opCtx, std::move(cursorParams));
invariant(!exec);
cursors.emplace_back(pin.getCursor());
pins.emplace_back(std::move(pin));
}
// If both explain and cursor are specified, explain wins.
if (expCtx->explain) {
auto explainExecutor = pins[0].getCursor()->getExecutor();
auto bodyBuilder = result->getBodyBuilder();
if (isPipelineExecutor(explainExecutor)) {
Explain::explainPipelineExecutor(explainExecutor, *(expCtx->explain), &bodyBuilder);
} else {
invariant(pins[0].getCursor()->lockPolicy() ==
ClientCursorParams::LockPolicy::kLockExternally);
invariant(!explainExecutor->isDetached());
invariant(explainExecutor->getOpCtx() == opCtx);
// The explainStages() function for a non-pipeline executor expects to be called with
// the appropriate collection lock already held. Make sure it has not been released yet.
invariant(ctx);
Explain::explainStages(explainExecutor,
ctx->getCollection(),
*(expCtx->explain),
BSON("optimizedPipeline" << true),
&bodyBuilder);
}
} else {
// Cursor must be specified, if explain is not.
const bool keepCursor =
handleCursorCommand(opCtx, origNss, std::move(cursors), request, result);
if (keepCursor) {
cursorFreer.dismiss();
}
PlanSummaryStats stats;
Explain::getSummaryStats(*(pins[0].getCursor()->getExecutor()), &stats);
curOp->debug().setPlanSummaryMetrics(stats);
curOp->debug().nreturned = stats.nReturned;
// For an optimized away pipeline, signal the cache that a query operation has completed.
// For normal pipelines this is done in DocumentSourceCursor.
if (ctx && ctx->getCollection()) {
ctx->getCollection()->infoCache()->notifyOfQuery(opCtx, stats.indexesUsed);
}
}
// Any code that needs the cursor pinned must be inside the try block, above.
return Status::OK();
}
} // namespace mongo
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