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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 <type_traits>
#include "mongo/db/pipeline/document_source.h"
#include "mongo/db/pipeline/document_source_change_stream_gen.h"
#include "mongo/db/pipeline/document_source_match.h"
#include "mongo/db/pipeline/document_source_single_document_transformation.h"
#include "mongo/db/pipeline/field_path.h"
#include "mongo/db/pipeline/resume_token.h"
#include "mongo/util/intrusive_counter.h"
namespace mongo {
/**
* The $changeStream stage is an alias for a cursor on oplog followed by a $match stage and a
* transform stage on mongod.
*/
class DocumentSourceChangeStream final {
public:
class LiteParsed final : public LiteParsedDocumentSource {
public:
static std::unique_ptr<LiteParsed> parse(const NamespaceString& nss,
const BSONElement& spec) {
return std::make_unique<LiteParsed>(spec.fieldName(), nss);
}
explicit LiteParsed(std::string parseTimeName, NamespaceString nss)
: LiteParsedDocumentSource(std::move(parseTimeName)), _nss(std::move(nss)) {}
bool isChangeStream() const final {
return true;
}
bool allowedToPassthroughFromMongos() const final {
return false;
}
stdx::unordered_set<NamespaceString> getInvolvedNamespaces() const final {
return stdx::unordered_set<NamespaceString>();
}
ActionSet actions{ActionType::changeStream, ActionType::find};
PrivilegeVector requiredPrivileges(bool isMongos,
bool bypassDocumentValidation) const final {
if (_nss.isAdminDB() && _nss.isCollectionlessAggregateNS()) {
// Watching a whole cluster.
return {Privilege(ResourcePattern::forAnyNormalResource(), actions)};
} else if (_nss.isCollectionlessAggregateNS()) {
// Watching a whole database.
return {Privilege(ResourcePattern::forDatabaseName(_nss.db()), actions)};
} else {
// Watching a single collection. Note if this is in the admin database it will fail
// at parse time.
return {Privilege(ResourcePattern::forExactNamespace(_nss), actions)};
}
}
ReadConcernSupportResult supportsReadConcern(repl::ReadConcernLevel level) const {
// Change streams require "majority" readConcern. If the client did not specify an
// explicit readConcern, change streams will internally upconvert the readConcern to
// majority (so clients can always send aggregations without readConcern). We therefore
// do not permit the cluster-wide default to be applied.
return onlySingleReadConcernSupported(
kStageName, repl::ReadConcernLevel::kMajorityReadConcern, level);
}
void assertSupportsMultiDocumentTransaction() const {
transactionNotSupported(kStageName);
}
private:
const NamespaceString _nss;
};
// The name of the field where the document key (_id and shard key, if present) will be found
// after the transformation.
static constexpr StringData kDocumentKeyField = "documentKey"_sd;
// The name of the field where the pre-image document will be found, if requested and available.
static constexpr StringData kFullDocumentBeforeChangeField = "fullDocumentBeforeChange"_sd;
// The name of the field where the full document will be found after the transformation. The
// full document is only present for certain types of operations, such as an insert.
static constexpr StringData kFullDocumentField = "fullDocument"_sd;
// The name of the field where the change identifier will be located after the transformation.
static constexpr StringData kIdField = "_id"_sd;
// The name of the field where the namespace of the change will be located after the
// transformation.
static constexpr StringData kNamespaceField = "ns"_sd;
// Name of the field which stores information about updates. Only applies when OperationType
// is "update".
static constexpr StringData kUpdateDescriptionField = "updateDescription"_sd;
// The name of the subfield of '_id' where the UUID of the namespace will be located after the
// transformation.
static constexpr StringData kUuidField = "uuid"_sd;
// The name of the field where the type of the operation will be located after the
// transformation.
static constexpr StringData kOperationTypeField = "operationType"_sd;
// The name of the field where the clusterTime of the change will be located after the
// transformation. The cluster time will be located inside the change identifier, so the full
// path to the cluster time will be kIdField + "." + kClusterTimeField.
static constexpr StringData kClusterTimeField = "clusterTime"_sd;
// The name of this stage.
static constexpr StringData kStageName = "$changeStream"_sd;
static constexpr StringData kTxnNumberField = "txnNumber"_sd;
static constexpr StringData kLsidField = "lsid"_sd;
// The target namespace of a rename operation.
static constexpr StringData kRenameTargetNssField = "to"_sd;
// The different types of operations we can use for the operation type.
static constexpr StringData kUpdateOpType = "update"_sd;
static constexpr StringData kDeleteOpType = "delete"_sd;
static constexpr StringData kReplaceOpType = "replace"_sd;
static constexpr StringData kInsertOpType = "insert"_sd;
static constexpr StringData kDropCollectionOpType = "drop"_sd;
static constexpr StringData kRenameCollectionOpType = "rename"_sd;
static constexpr StringData kDropDatabaseOpType = "dropDatabase"_sd;
static constexpr StringData kInvalidateOpType = "invalidate"_sd;
// Internal op type to signal mongos to open cursors on new shards.
static constexpr StringData kNewShardDetectedOpType = "kNewShardDetected"_sd;
enum class ChangeStreamType { kSingleCollection, kSingleDatabase, kAllChangesForCluster };
/**
* Helpers for Determining which regex to match a change stream against.
*/
static ChangeStreamType getChangeStreamType(const NamespaceString& nss);
static std::string getNsRegexForChangeStream(const NamespaceString& nss);
/**
* Produce the BSON object representing the filter for the $match stage to filter oplog entries
* to only those relevant for this $changeStream stage.
*/
static BSONObj buildMatchFilter(const boost::intrusive_ptr<ExpressionContext>& expCtx,
Timestamp startFrom,
bool showMigrationEvents);
/**
* Parses a $changeStream stage from 'elem' and produces the $match and transformation
* stages required.
*/
static std::list<boost::intrusive_ptr<DocumentSource>> createFromBson(
BSONElement elem, const boost::intrusive_ptr<ExpressionContext>& expCtx);
/**
* Given a BSON object containing an aggregation command with a $changeStream stage, and a
* resume token, returns a new BSON object with the same command except with the addition of a
* resumeAfter: option containing the resume token. If there was a previous resumeAfter:
* option, it is removed.
*/
static BSONObj replaceResumeTokenInCommand(BSONObj originalCmdObj, Document resumeToken);
/**
* Helper used by various change stream stages. Used for asserting that a certain Value of a
* field has a certain type. Will uassert() if the field does not have the expected type.
*/
static void checkValueType(const Value v, const StringData fieldName, BSONType expectedType);
private:
static constexpr StringData kRegexAllCollections = R"((?!(\$|system\.)))"_sd;
static constexpr StringData kRegexAllDBs = R"(^(?!(admin|config|local)\.)[^.]+)"_sd;
static constexpr StringData kRegexCmdColl = R"(\$cmd$)"_sd;
// Helper function which throws if the $changeStream fails any of a series of semantic checks.
// For instance, whether it is permitted to run given the current FCV, whether the namespace is
// valid for the options specified in the spec, etc.
static void assertIsLegalSpecification(const boost::intrusive_ptr<ExpressionContext>& expCtx,
const DocumentSourceChangeStreamSpec& spec);
// It is illegal to construct a DocumentSourceChangeStream directly, use createFromBson()
// instead.
DocumentSourceChangeStream() = default;
};
/**
* A custom subclass of DocumentSourceMatch which does not serialize itself (since it came from an
* alias) and requires itself to be the first stage in the pipeline.
*/
class DocumentSourceOplogMatch final : public DocumentSourceMatch {
public:
DocumentSourceOplogMatch(const DocumentSourceOplogMatch& other) : DocumentSourceMatch(other) {}
virtual boost::intrusive_ptr<DocumentSourceMatch> clone() const {
return make_intrusive<std::decay_t<decltype(*this)>>(*this);
}
static boost::intrusive_ptr<DocumentSourceOplogMatch> create(
BSONObj filter, const boost::intrusive_ptr<ExpressionContext>& expCtx);
const char* getSourceName() const final;
GetNextResult doGetNext() final {
// We should never execute this stage directly. We expect this stage to be absorbed into the
// cursor feeding the pipeline, and executing this stage may result in the use of the wrong
// collation. The comparisons against the oplog must use the simple collation, regardless of
// the collation on the ExpressionContext.
MONGO_UNREACHABLE;
}
StageConstraints constraints(Pipeline::SplitState pipeState) const final;
Value serialize(boost::optional<ExplainOptions::Verbosity> explain) const final;
private:
using DocumentSourceMatch::DocumentSourceMatch;
};
} // namespace mongo
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