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/**
* Copyright (C) 2017 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 <http://www.gnu.org/licenses/>.
*
* 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::kCommand
#include "mongo/platform/basic.h"
#include "mongo/db/commands/run_aggregate.h"
#include <boost/optional.hpp>
#include <vector>
#include "mongo/db/catalog/database.h"
#include "mongo/db/curop.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/exec/pipeline_proxy.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/pipeline/accumulator.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/pipeline/document_source.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/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/service_context.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/db/views/view.h"
#include "mongo/db/views/view_catalog.h"
#include "mongo/db/views/view_sharding_check.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.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 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. In the case of views, this can be different from that
* in 'request'.
*/
bool handleCursorCommand(OperationContext* opCtx,
const string& nsForCursor,
ClientCursor* cursor,
PlanExecutor* exec,
const AggregationRequest& request,
BSONObjBuilder& result) {
if (cursor) {
invariant(cursor->getExecutor() == exec);
invariant(cursor->isAggCursor());
}
long long batchSize = request.getBatchSize();
// can't use result BSONObjBuilder directly since it won't handle exceptions correctly.
BSONArrayBuilder resultsArray;
BSONObj next;
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;
if ((state = exec->getNext(&next, NULL)) == PlanExecutor::IS_EOF) {
// make it an obvious error to use cursor or executor after this point
cursor = NULL;
exec = NULL;
break;
}
uassert(34426,
"Plan executor error during aggregation: " + WorkingSetCommon::toStatusString(next),
PlanExecutor::ADVANCED == state);
// If adding this object will cause us to exceed the message size limit, then we stash it
// for later.
if (!FindCommon::haveSpaceForNext(next, objCount, resultsArray.len())) {
exec->enqueue(next);
break;
}
resultsArray.append(next);
}
// NOTE: exec->isEOF() can have side effects such as writing by $out. However, it should
// be relatively quick since if there was no cursor then the input is empty. Also, this
// violates the contract for batchSize==0. Sharding requires a cursor to be returned in that
// case. This is ok for now however, since you can't have a sharded collection that doesn't
// exist.
const bool canReturnMoreBatches = cursor;
if (!canReturnMoreBatches && exec && !exec->isEOF()) {
// msgasserting since this shouldn't be possible to trigger from today's aggregation
// language. The wording assumes that the only reason cursor would be null is if the
// collection doesn't exist.
msgasserted(
17391,
str::stream() << "Aggregation has more results than fit in initial batch, but can't "
<< "create cursor since collection "
<< nsForCursor
<< " doesn't exist");
}
if (cursor) {
// 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::get(opCtx)->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::get(opCtx)->debug().cursorExhausted = true;
}
const long long cursorId = cursor ? cursor->cursorid() : 0LL;
appendCursorResponseObject(cursorId, nsForCursor, resultsArray.arr(), &result);
return static_cast<bool>(cursor);
}
StatusWith<StringMap<ExpressionContext::ResolvedNamespace>> resolveInvolvedNamespaces(
OperationContext* opCtx, const AggregationRequest& request) {
// 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 ? db->getViewCatalog() : nullptr;
const LiteParsedPipeline liteParsedPipeline(request);
const auto& pipelineInvolvedNamespaces = liteParsedPipeline.getInvolvedNamespaces();
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 (!db || db->getCollection(involvedNs.ns())) {
// If the 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;
}
/**
* Round trips the pipeline through serialization by calling serialize(), then Pipeline::parse().
* fasserts if it fails to parse after being serialized.
*/
boost::intrusive_ptr<Pipeline> reparsePipeline(
const boost::intrusive_ptr<Pipeline>& pipeline,
const AggregationRequest& request,
const boost::intrusive_ptr<ExpressionContext>& expCtx) {
auto serialized = pipeline->serialize();
// Convert vector<Value> to vector<BSONObj>.
std::vector<BSONObj> parseableSerialization;
parseableSerialization.reserve(serialized.size());
for (auto&& serializedStage : serialized) {
invariant(serializedStage.getType() == BSONType::Object);
parseableSerialization.push_back(serializedStage.getDocument().toBson());
}
auto reparsedPipeline = Pipeline::parse(parseableSerialization, expCtx);
if (!reparsedPipeline.isOK()) {
error() << "Aggregation command did not round trip through parsing and serialization "
"correctly. Input pipeline: "
<< Value(request.getPipeline()) << ", serialized pipeline: " << Value(serialized);
fassertFailedWithStatusNoTrace(40175, reparsedPipeline.getStatus());
}
reparsedPipeline.getValue()->optimizePipeline();
return reparsedPipeline.getValue();
}
/**
* 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 intrusive_ptr<Pipeline> pipeline) {
if (!db || !pipeline) {
return Status::OK();
}
for (auto&& potentialViewNs : pipeline->getInvolvedCollections()) {
if (db->getCollection(potentialViewNs.ns())) {
continue;
}
auto view = db->getViewCatalog()->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();
}
} // namespace
Status runAggregate(OperationContext* opCtx,
const NamespaceString& origNss,
const AggregationRequest& request,
const BSONObj& cmdObj,
BSONObjBuilder& result) {
// For operations on views, this will be the underlying namespace.
const NamespaceString& nss = request.getNamespaceString();
// Parse the user-specified collation, if any.
std::unique_ptr<CollatorInterface> userSpecifiedCollator = request.getCollation().isEmpty()
? nullptr
: uassertStatusOK(CollatorFactoryInterface::get(opCtx->getServiceContext())
->makeFromBSON(request.getCollation()));
boost::optional<ClientCursorPin> pin; // either this OR the exec will be non-null
unique_ptr<PlanExecutor> exec;
boost::intrusive_ptr<ExpressionContext> expCtx;
boost::intrusive_ptr<Pipeline> pipeline;
auto curOp = CurOp::get(opCtx);
{
// This 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 aggregation.
// Otherwise, the lock must be held continuously from now until we have we created both
// the output ClientCursor and the input executor. This ensures that both are using the
// same sharding version that we synchronize on here. This is also why we always need to
// create a ClientCursor even when we aren't outputting to a cursor. See the comment on
// ShardFilterStage for more details.
AutoGetCollectionOrViewForReadCommand ctx(opCtx, nss);
Collection* collection = ctx.getCollection();
// 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.)
const LiteParsedPipeline liteParsedPipeline(request);
if (ctx.getView() && !liteParsedPipeline.startsWithCollStats()) {
// Check that the default collation of 'view' is compatible with the operation's
// collation. The check is skipped if the 'request' has the empty collation, which
// means that no collation was specified.
if (!request.getCollation().isEmpty()) {
if (!CollatorInterface::collatorsMatch(ctx.getView()->defaultCollator(),
userSpecifiedCollator.get())) {
return {ErrorCodes::OptionNotSupportedOnView,
"Cannot override a view's default collation"};
}
}
auto viewDefinition =
ViewShardingCheck::getResolvedViewIfSharded(opCtx, ctx.getDb(), ctx.getView());
if (!viewDefinition.isOK()) {
return viewDefinition.getStatus();
}
if (!viewDefinition.getValue().isEmpty()) {
return ViewShardingCheck::appendShardedViewResponse(viewDefinition.getValue(),
&result);
}
auto resolvedView = ctx.getDb()->getViewCatalog()->resolveView(opCtx, nss);
if (!resolvedView.isOK()) {
return resolvedView.getStatus();
}
auto collationSpec = ctx.getView()->defaultCollator()
? ctx.getView()->defaultCollator()->getSpec().toBSON().getOwned()
: CollationSpec::kSimpleSpec;
// With the view & collation resolved, we can relinquish locks.
ctx.releaseLocksForView();
// Parse the resolved view into a new aggregation request.
auto newRequest = resolvedView.getValue().asExpandedViewAggregation(request);
newRequest.setCollation(collationSpec);
auto newCmd = newRequest.serializeToCommandObj().toBson();
auto status = runAggregate(opCtx, origNss, newRequest, newCmd, 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;
}
// Determine the appropriate collation to make the ExpressionContext.
// If the pipeline does not have a user-specified collation, set it from the collection
// default. Be careful to consult the original request BSON to check if a collation was
// specified, since a specification of {locale: "simple"} will result in a null
// collator.
auto collatorToUse = std::move(userSpecifiedCollator);
if (request.getCollation().isEmpty() && collection && collection->getDefaultCollator()) {
invariant(!collatorToUse);
collatorToUse = collection->getDefaultCollator()->clone();
}
expCtx.reset(
new ExpressionContext(opCtx,
request,
std::move(collatorToUse),
uassertStatusOK(resolveInvolvedNamespaces(opCtx, request))));
expCtx->tempDir = storageGlobalParams.dbpath + "/_tmp";
// Parse the pipeline.
auto statusWithPipeline = Pipeline::parse(request.getPipeline(), expCtx);
if (!statusWithPipeline.isOK()) {
return statusWithPipeline.getStatus();
}
pipeline = std::move(statusWithPipeline.getValue());
// Check that the view's collation matches the collation of any views involved
// in the pipeline.
auto pipelineCollationStatus =
collatorCompatibleWithPipeline(opCtx, ctx.getDb(), expCtx->getCollator(), pipeline);
if (!pipelineCollationStatus.isOK()) {
return pipelineCollationStatus;
}
pipeline->optimizePipeline();
if (kDebugBuild && !expCtx->explain && !expCtx->inShard) {
// Make sure all operations round-trip through Pipeline::serialize() correctly by
// re-parsing every command in debug builds. This is important because sharded
// aggregations rely on this ability. Skipping when inShard because this has
// already been through the transformation (and this un-sets expCtx->inShard).
pipeline = reparsePipeline(pipeline, request, expCtx);
}
// This does mongod-specific stuff like creating the input PlanExecutor and adding
// it to the front of the pipeline if needed.
PipelineD::prepareCursorSource(collection, &request, pipeline);
// Create the PlanExecutor which returns results from the pipeline. The WorkingSet
// ('ws') and the PipelineProxyStage ('proxy') will be owned by the created
// PlanExecutor.
auto ws = make_unique<WorkingSet>();
auto proxy = make_unique<PipelineProxyStage>(opCtx, pipeline, ws.get());
auto statusWithPlanExecutor = (NULL == collection)
? PlanExecutor::make(
opCtx, std::move(ws), std::move(proxy), nss.ns(), PlanExecutor::YIELD_MANUAL)
: PlanExecutor::make(
opCtx, std::move(ws), std::move(proxy), collection, PlanExecutor::YIELD_MANUAL);
invariant(statusWithPlanExecutor.isOK());
exec = std::move(statusWithPlanExecutor.getValue());
{
auto planSummary = Explain::getPlanSummary(exec.get());
stdx::lock_guard<Client> lk(*opCtx->getClient());
curOp->setPlanSummary_inlock(std::move(planSummary));
}
if (collection) {
const bool isAggCursor = true; // enable special locking behavior
pin.emplace(collection->getCursorManager()->registerCursor(
{exec.release(),
nss.ns(),
opCtx->recoveryUnit()->isReadingFromMajorityCommittedSnapshot(),
0,
cmdObj.getOwned(),
isAggCursor}));
// Don't add any code between here and the start of the try block.
}
// At this point, it is safe to release the collection lock.
// - In the case where we have a collection: we will need to reacquire the
// collection lock later when cleaning up our ClientCursorPin.
// - In the case where we don't have a collection: our PlanExecutor won't be
// registered, so it will be safe to clean it up outside the lock.
invariant(!exec || !collection);
}
try {
// Unless set to true, the ClientCursor created above will be deleted on block exit.
bool keepCursor = false;
// If both explain and cursor are specified, explain wins.
if (expCtx->explain) {
result << "stages" << Value(pipeline->writeExplainOps(*expCtx->explain));
} else {
// Cursor must be specified, if explain is not.
keepCursor = handleCursorCommand(opCtx,
origNss.ns(),
pin ? pin->getCursor() : nullptr,
pin ? pin->getCursor()->getExecutor() : exec.get(),
request,
result);
}
if (!expCtx->explain) {
PlanSummaryStats stats;
Explain::getSummaryStats(pin ? *pin->getCursor()->getExecutor() : *exec.get(), &stats);
curOp->debug().setPlanSummaryMetrics(stats);
curOp->debug().nreturned = stats.nReturned;
}
// Clean up our ClientCursorPin, if needed. We must reacquire the collection lock
// in order to do so.
if (pin) {
// We acquire locks here with DBLock and CollectionLock instead of using
// AutoGetCollectionForRead. AutoGetCollectionForRead will throw if the
// sharding version is out of date, and we don't care if the sharding version
// has changed.
Lock::DBLock dbLock(opCtx, nss.db(), MODE_IS);
Lock::CollectionLock collLock(opCtx->lockState(), nss.ns(), MODE_IS);
if (keepCursor) {
pin->release();
} else {
pin->deleteUnderlying();
}
}
} catch (...) {
// On our way out of scope, we clean up our ClientCursorPin if needed.
if (pin) {
Lock::DBLock dbLock(opCtx, nss.db(), MODE_IS);
Lock::CollectionLock collLock(opCtx->lockState(), nss.ns(), MODE_IS);
pin->deleteUnderlying();
}
throw;
}
// Any code that needs the cursor pinned must be inside the try block, above.
return Status::OK();
}
} // namespace mongo
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