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/**
* Copyright (C) 2022-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 "mongo/db/exec/batched_delete_stage_gen.h"
#include "mongo/db/exec/delete_stage.h"
#include "mongo/db/exec/write_stage_common.h"
#include "mongo/db/jsobj.h"
namespace mongo {
/**
* Batch sizing parameters. A batch of documents staged for deletion is committed as soon
* as one of the targets below is met, or upon reaching EOF.
*/
struct BatchedDeleteStageBatchParams {
BatchedDeleteStageBatchParams()
: targetBatchBytes(gBatchedDeletesTargetBatchBytes.load()),
targetBatchDocs(gBatchedDeletesTargetBatchDocs.load()),
targetBatchTimeMS(Milliseconds(gBatchedDeletesTargetBatchTimeMS.load())) {}
// Documents staged for deletions are processed in a batch once this batch size target is met.
// Accounts for documents and indexes. A value of zero means unlimited.
long long targetBatchBytes = 0;
// Documents staged for deletions are processed in a batch once this document count target is
// met. A value of zero means unlimited.
long long targetBatchDocs = 0;
// A batch is committed as soon as this target execution time is met. Zero means unlimited.
Milliseconds targetBatchTimeMS = Milliseconds(0);
};
/**
* The BATCHED_DELETE stage deletes documents in batches, using RecordId's that are returned from
* its child. In comparison, the base class DeleteStage deletes documents one by one. The stage
* returns NEED_TIME after deleting a document, or after staging a document to be deleted in the
* next batch.
*
* Callers of work() must be holding a write lock (and, for replicated deletes, callers must have
* had the replication coordinator approve the write).
*/
class BatchedDeleteStage final : public DeleteStage {
BatchedDeleteStage(const BatchedDeleteStage&) = delete;
BatchedDeleteStage& operator=(const BatchedDeleteStage&) = delete;
public:
static constexpr StringData kStageType = "BATCHED_DELETE"_sd;
BatchedDeleteStage(ExpressionContext* expCtx,
std::unique_ptr<DeleteStageParams> params,
std::unique_ptr<BatchedDeleteStageBatchParams> batchParams,
WorkingSet* ws,
const CollectionPtr& collection,
PlanStage* child);
~BatchedDeleteStage();
StageState doWork(WorkingSetID* out);
StageType stageType() const final {
return STAGE_BATCHED_DELETE;
}
private:
/**
* Returns NEED_YIELD when there is a write conflict. Otherwise, returns NEED_TIME when
* some, or all, of the documents staged in the _stagedDeletesBuffer are successfully deleted.
*/
PlanStage::StageState _deleteBatch(WorkingSetID* out);
// Tries to restore the child's state. Returns NEED_TIME if the restore succeeds, NEED_YIELD
// upon write conflict.
PlanStage::StageState _tryRestoreState(WorkingSetID* out);
// Prepares to retry draining the _stagedDeletesBuffer after a write conflict. Removes
// 'recordsThatNoLongerMatch' then yields.
PlanStage::StageState _prepareToRetryDrainAfterWCE(
WorkingSetID* out, const std::set<RecordId>& recordsThatNoLongerMatch);
// Metadata of a document staged for deletion.
struct StagedDocumentMetadata {
RecordId rid;
// SnapshotId associated with the document when it is staged for deletion. Must be checked
// before deletion to ensure the document still matches the query.
SnapshotId snapshotId;
};
// Stores documents staged for deletion.
std::vector<StagedDocumentMetadata> _stagedDeletesBuffer;
// Whether there are remaining docs in the buffer from a previous call to doWork() that should
// be drained before fetching more documents.
bool _drainRemainingBuffer = false;
// Batch targeting parameters.
std::unique_ptr<BatchedDeleteStageBatchParams> _batchParams;
};
} // namespace mongo
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