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/**
* Copyright 2011 (c) 10gen 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.
*/
#include "mongo/platform/basic.h"
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/catalog/database_holder.h"
#include "mongo/db/db_raii.h"
#include "mongo/db/exec/working_set_common.h"
#include "mongo/db/instance.h"
#include "mongo/db/pipeline/document.h"
#include "mongo/db/query/explain.h"
#include "mongo/db/query/find_common.h"
#include "mongo/db/storage/storage_options.h"
#include "mongo/s/d_state.h"
namespace mongo {
using boost::intrusive_ptr;
using std::shared_ptr;
using std::string;
DocumentSourceCursor::~DocumentSourceCursor() {
dispose();
}
const char* DocumentSourceCursor::getSourceName() const {
return "$cursor";
}
boost::optional<Document> DocumentSourceCursor::getNext() {
pExpCtx->checkForInterrupt();
if (_currentBatch.empty()) {
loadBatch();
if (_currentBatch.empty()) // exhausted the cursor
return boost::none;
}
Document out = _currentBatch.front();
_currentBatch.pop_front();
return out;
}
void DocumentSourceCursor::dispose() {
// Can't call in to PlanExecutor or ClientCursor registries from this function since it
// will be called when an agg cursor is killed which would cause a deadlock.
_exec.reset();
_currentBatch.clear();
}
void DocumentSourceCursor::loadBatch() {
if (!_exec) {
dispose();
return;
}
// We have already validated the sharding version when we constructed the PlanExecutor
// so we shouldn't check it again.
const NamespaceString nss(_ns);
AutoGetCollectionForRead autoColl(pExpCtx->opCtx, nss);
_exec->restoreState();
int memUsageBytes = 0;
BSONObj obj;
PlanExecutor::ExecState state;
while ((state = _exec->getNext(&obj, NULL)) == PlanExecutor::ADVANCED) {
if (_dependencies) {
_currentBatch.push_back(_dependencies->extractFields(obj));
} else {
_currentBatch.push_back(Document::fromBsonWithMetaData(obj));
}
if (_limit) {
if (++_docsAddedToBatches == _limit->getLimit()) {
break;
}
verify(_docsAddedToBatches < _limit->getLimit());
}
memUsageBytes += _currentBatch.back().getApproximateSize();
if (memUsageBytes > FindCommon::kMaxBytesToReturnToClientAtOnce) {
// End this batch and prepare PlanExecutor for yielding.
_exec->saveState();
return;
}
}
// If we got here, there won't be any more documents, so destroy the executor. Can't use
// dispose since we want to keep the _currentBatch.
_exec.reset();
uassert(16028,
str::stream() << "collection or index disappeared when cursor yielded: "
<< WorkingSetCommon::toStatusString(obj),
state != PlanExecutor::DEAD);
uassert(
17285,
str::stream() << "cursor encountered an error: " << WorkingSetCommon::toStatusString(obj),
state != PlanExecutor::FAILURE);
massert(17286,
str::stream() << "Unexpected return from PlanExecutor::getNext: " << state,
state == PlanExecutor::IS_EOF || state == PlanExecutor::ADVANCED);
}
long long DocumentSourceCursor::getLimit() const {
return _limit ? _limit->getLimit() : -1;
}
bool DocumentSourceCursor::coalesce(const intrusive_ptr<DocumentSource>& nextSource) {
// Note: Currently we assume the $limit is logically after any $sort or
// $match. If we ever pull in $match or $sort using this method, we
// will need to keep track of the order of the sub-stages.
if (!_limit) {
_limit = dynamic_cast<DocumentSourceLimit*>(nextSource.get());
return _limit.get(); // false if next is not a $limit
} else {
return _limit->coalesce(nextSource);
}
return false;
}
Value DocumentSourceCursor::serialize(bool explain) const {
// we never parse a documentSourceCursor, so we only serialize for explain
if (!explain)
return Value();
// Get planner-level explain info from the underlying PlanExecutor.
BSONObjBuilder explainBuilder;
{
const NamespaceString nss(_ns);
AutoGetCollectionForRead autoColl(pExpCtx->opCtx, nss);
massert(17392, "No _exec. Were we disposed before explained?", _exec);
_exec->restoreState();
Explain::explainStages(_exec.get(), ExplainCommon::QUERY_PLANNER, &explainBuilder);
_exec->saveState();
}
MutableDocument out;
out["query"] = Value(_query);
if (!_sort.isEmpty())
out["sort"] = Value(_sort);
if (_limit)
out["limit"] = Value(_limit->getLimit());
if (!_projection.isEmpty())
out["fields"] = Value(_projection);
// Add explain results from the query system into the agg explain output.
BSONObj explainObj = explainBuilder.obj();
invariant(explainObj.hasField("queryPlanner"));
out["queryPlanner"] = Value(explainObj["queryPlanner"]);
return Value(DOC(getSourceName() << out.freezeToValue()));
}
DocumentSourceCursor::DocumentSourceCursor(const string& ns,
const std::shared_ptr<PlanExecutor>& exec,
const intrusive_ptr<ExpressionContext>& pCtx)
: DocumentSource(pCtx), _docsAddedToBatches(0), _ns(ns), _exec(exec) {}
intrusive_ptr<DocumentSourceCursor> DocumentSourceCursor::create(
const string& ns,
const std::shared_ptr<PlanExecutor>& exec,
const intrusive_ptr<ExpressionContext>& pExpCtx) {
return new DocumentSourceCursor(ns, exec, pExpCtx);
}
void DocumentSourceCursor::setProjection(const BSONObj& projection,
const boost::optional<ParsedDeps>& deps) {
_projection = projection;
_dependencies = deps;
}
}
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