014fd55adc
Summary: This patch fixes #7460559. It introduces SingleDelete as a new database operation. This operation can be used to delete keys that were never overwritten (no put following another put of the same key). If an overwritten key is single deleted the behavior is undefined. Single deletion of a non-existent key has no effect but multiple consecutive single deletions are not allowed (see limitations). In contrast to the conventional Delete() operation, the deletion entry is removed along with the value when the two are lined up in a compaction. Note: The semantics are similar to @igor's prototype that allowed to have this behavior on the granularity of a column family ( https://reviews.facebook.net/D42093 ). This new patch, however, is more aggressive when it comes to removing tombstones: It removes the SingleDelete together with the value whenever there is no snapshot between them while the older patch only did this when the sequence number of the deletion was older than the earliest snapshot. Most of the complex additions are in the Compaction Iterator, all other changes should be relatively straightforward. The patch also includes basic support for single deletions in db_stress and db_bench. Limitations: - Not compatible with cuckoo hash tables - Single deletions cannot be used in combination with merges and normal deletions on the same key (other keys are not affected by this) - Consecutive single deletions are currently not allowed (and older version of this patch supported this so it could be resurrected if needed) Test Plan: make all check Reviewers: yhchiang, sdong, rven, anthony, yoshinorim, igor Reviewed By: igor Subscribers: maykov, dhruba, leveldb Differential Revision: https://reviews.facebook.net/D43179
100 lines
4.2 KiB
C++
100 lines
4.2 KiB
C++
// Copyright (c) 2015, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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namespace rocksdb {
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class Slice;
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class Status;
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class ColumnFamilyHandle;
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class WriteBatch;
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struct SliceParts;
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// Abstract base class that defines the basic interface for a write batch.
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// See WriteBatch for a basic implementation and WrithBatchWithIndex for an
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// indexed implemenation.
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class WriteBatchBase {
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public:
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virtual ~WriteBatchBase() {}
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// Store the mapping "key->value" in the database.
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virtual void Put(ColumnFamilyHandle* column_family, const Slice& key,
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const Slice& value) = 0;
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virtual void Put(const Slice& key, const Slice& value) = 0;
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// Variant of Put() that gathers output like writev(2). The key and value
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// that will be written to the database are concatentations of arrays of
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// slices.
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virtual void Put(ColumnFamilyHandle* column_family, const SliceParts& key,
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const SliceParts& value);
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virtual void Put(const SliceParts& key, const SliceParts& value);
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// Merge "value" with the existing value of "key" in the database.
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// "key->merge(existing, value)"
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virtual void Merge(ColumnFamilyHandle* column_family, const Slice& key,
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const Slice& value) = 0;
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virtual void Merge(const Slice& key, const Slice& value) = 0;
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// variant that takes SliceParts
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virtual void Merge(ColumnFamilyHandle* column_family, const SliceParts& key,
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const SliceParts& value);
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virtual void Merge(const SliceParts& key, const SliceParts& value);
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// If the database contains a mapping for "key", erase it. Else do nothing.
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virtual void Delete(ColumnFamilyHandle* column_family, const Slice& key) = 0;
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virtual void Delete(const Slice& key) = 0;
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// variant that takes SliceParts
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virtual void Delete(ColumnFamilyHandle* column_family, const SliceParts& key);
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virtual void Delete(const SliceParts& key);
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// If the database contains a mapping for "key", erase it. Expects that the
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// key was not overwritten. Else do nothing.
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virtual void SingleDelete(ColumnFamilyHandle* column_family,
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const Slice& key) = 0;
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virtual void SingleDelete(const Slice& key) = 0;
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// variant that takes SliceParts
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virtual void SingleDelete(ColumnFamilyHandle* column_family,
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const SliceParts& key);
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virtual void SingleDelete(const SliceParts& key);
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// Append a blob of arbitrary size to the records in this batch. The blob will
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// be stored in the transaction log but not in any other file. In particular,
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// it will not be persisted to the SST files. When iterating over this
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// WriteBatch, WriteBatch::Handler::LogData will be called with the contents
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// of the blob as it is encountered. Blobs, puts, deletes, and merges will be
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// encountered in the same order in thich they were inserted. The blob will
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// NOT consume sequence number(s) and will NOT increase the count of the batch
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//
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// Example application: add timestamps to the transaction log for use in
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// replication.
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virtual void PutLogData(const Slice& blob) = 0;
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// Clear all updates buffered in this batch.
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virtual void Clear() = 0;
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// Covert this batch into a WriteBatch. This is an abstracted way of
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// converting any WriteBatchBase(eg WriteBatchWithIndex) into a basic
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// WriteBatch.
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virtual WriteBatch* GetWriteBatch() = 0;
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// Records the state of the batch for future calls to RollbackToSavePoint().
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// May be called multiple times to set multiple save points.
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virtual void SetSavePoint() = 0;
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// Remove all entries in this batch (Put, Merge, Delete, PutLogData) since the
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// most recent call to SetSavePoint() and removes the most recent save point.
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// If there is no previous call to SetSavePoint(), behaves the same as
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// Clear().
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virtual Status RollbackToSavePoint() = 0;
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};
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} // namespace rocksdb
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