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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.
*/
#pragma once
#include <boost/intrusive_ptr.hpp>
#include <memory>
#include "mongo/bson/bsonobj.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/pipeline/aggregation_request.h"
#include "mongo/db/pipeline/dependencies.h"
#include "mongo/db/pipeline/document_source_cursor.h"
#include "mongo/db/pipeline/document_source_group.h"
#include "mongo/db/query/collation/collator_factory_interface.h"
#include "mongo/db/query/plan_executor.h"
namespace mongo {
class Collection;
class DocumentSourceCursor;
class DocumentSourceMatch;
class DocumentSourceSort;
class ExpressionContext;
class OperationContext;
class Pipeline;
struct PlanSummaryStats;
/**
* PipelineD is an extension of the Pipeline class, but with additional material that references
* symbols that are not available in mongos, where the remainder of the Pipeline class also
* functions. PipelineD is a friend of Pipeline so that it can have equal access to Pipeline's
* members.
*
* See the friend declaration in Pipeline.
*/
class PipelineD {
public:
/**
* This callback function is called to attach a query PlanExecutor to the given Pipeline by
* creating a specific DocumentSourceCursor stage using the provided PlanExecutor, and adding
* the new stage to the pipeline.
*/
using AttachExecutorCallback = std::function<void(
Collection*, std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>, Pipeline*)>;
/**
* This method looks for early pipeline stages that can be folded into the underlying
* PlanExecutor, and removes those stages from the pipeline when they can be absorbed by the
* PlanExecutor. For example, an early $match can be removed and replaced with a
* DocumentSourceCursor containing a PlanExecutor that will do an index scan.
*
* Callers must take care to ensure that 'nss' is locked in at least IS-mode.
*
* When not null, 'aggRequest' provides access to pipeline command options such as hint.
*
* The 'collection' parameter is optional and can be passed as 'nullptr'.
*
* This method will not add a $cursor stage to the pipeline, but will create a PlanExecutor and
* a callback function. The executor and the callback can later be used to create the $cursor
* stage and add it to the pipeline by calling 'attachInnerQueryExecutorToPipeline()' method.
* If the pipeline doesn't require a $cursor stage, the plan executor will be returned as
* 'nullptr'.
*/
static std::pair<AttachExecutorCallback, std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>>
buildInnerQueryExecutor(Collection* collection,
const NamespaceString& nss,
const AggregationRequest* aggRequest,
Pipeline* pipeline);
/**
* Completes creation of the $cursor stage using the given callback pair obtained by calling
* 'buildInnerQueryExecutor()' method. If the callback doesn't hold a valid PlanExecutor, the
* method does nothing. Otherwise, a new $cursor stage is created using the given PlanExecutor,
* and added to the pipeline. The 'collection' parameter is optional and can be passed as
* 'nullptr'.
*/
static void attachInnerQueryExecutorToPipeline(
Collection* collection,
AttachExecutorCallback attachExecutorCallback,
std::unique_ptr<PlanExecutor, PlanExecutor::Deleter> exec,
Pipeline* pipeline);
/**
* This method combines 'buildInnerQueryExecutor()' and 'attachInnerQueryExecutorToPipeline()'
* into a single call to support auto completion of the cursor stage creation process. Can be
* used when the executor attachment phase doesn't need to be deferred and the $cursor stage
* can be created right after buiding the executor.
*/
static void buildAndAttachInnerQueryExecutorToPipeline(Collection* collection,
const NamespaceString& nss,
const AggregationRequest* aggRequest,
Pipeline* pipeline);
static std::string getPlanSummaryStr(const Pipeline* pipeline);
static void getPlanSummaryStats(const Pipeline* pipeline, PlanSummaryStats* statsOut);
static Timestamp getLatestOplogTimestamp(const Pipeline* pipeline);
/**
* Resolves the collator to either the user-specified collation or, if none was specified, to
* the collection-default collation.
*/
static std::unique_ptr<CollatorInterface> resolveCollator(OperationContext* opCtx,
BSONObj userCollation,
const Collection* collection) {
if (!userCollation.isEmpty()) {
return uassertStatusOK(CollatorFactoryInterface::get(opCtx->getServiceContext())
->makeFromBSON(userCollation));
}
return (collection && collection->getDefaultCollator()
? collection->getDefaultCollator()->clone()
: nullptr);
}
private:
PipelineD(); // does not exist: prevent instantiation
/**
* Build a PlanExecutor and prepare callback to create a generic DocumentSourceCursor for
* the 'pipeline'.
*/
static std::pair<AttachExecutorCallback, std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>>
buildInnerQueryExecutorGeneric(Collection* collection,
const NamespaceString& nss,
const AggregationRequest* aggRequest,
Pipeline* pipeline);
/**
* Build a PlanExecutor and prepare a callback to create a special DocumentSourceGeoNearCursor
* for the 'pipeline'. Unlike 'buildInnerQueryExecutorGeneric()', throws if 'collection' does
* not exist, as the $geoNearCursor requires a 2d or 2dsphere index.
*/
static std::pair<AttachExecutorCallback, std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>>
buildInnerQueryExecutorGeoNear(Collection* collection,
const NamespaceString& nss,
const AggregationRequest* aggRequest,
Pipeline* pipeline);
/**
* Creates a PlanExecutor to be used in the initial cursor source. This function will try to
* push down the $sort, $project, $match and $limit stages into the PlanStage layer whenever
* possible. In this case, these stages will be incorporated into the PlanExecutor.
*
* Set 'rewrittenGroupStage' when the pipeline uses $match+$sort+$group stages that are
* compatible with a DISTINCT_SCAN plan that visits the first document in each group
* (SERVER-9507).
*
* Sets the 'hasNoRequirements' out-parameter based on whether the dependency set is both finite
* and empty. In this case, the query has count semantics.
*/
static StatusWith<std::unique_ptr<PlanExecutor, PlanExecutor::Deleter>> prepareExecutor(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
Collection* collection,
const NamespaceString& nss,
Pipeline* pipeline,
const boost::intrusive_ptr<DocumentSourceSort>& sortStage,
std::unique_ptr<GroupFromFirstDocumentTransformation> rewrittenGroupStage,
QueryMetadataBitSet metadataAvailable,
const BSONObj& queryObj,
boost::optional<long long> limit,
const AggregationRequest* aggRequest,
const MatchExpressionParser::AllowedFeatureSet& matcherFeatures,
bool* hasNoRequirements);
/**
* Adds 'cursor' to the front of 'pipeline'. If 'shouldProduceEmptyDocs' is true, then we inform
* 'cursor' that this is a count scenario -- the dependency set is fully known and is empty. In
* this case, 'cursor' can return a sequence of empty documents for the caller to count.
*/
static void addCursorSource(Pipeline* pipeline,
boost::intrusive_ptr<DocumentSourceCursor> cursor,
bool shouldProduceEmptyDocs);
};
} // namespace mongo
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