3995e801ab
Summary: also add an override option total_order_iteration if you want to use full iterator with prefix_extractor Test Plan: make all check Reviewers: igor, haobo, sdong, yhchiang Reviewed By: haobo CC: leveldb, dhruba Differential Revision: https://reviews.facebook.net/D17805
98 lines
2.9 KiB
C++
98 lines
2.9 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under the BSD-style license found in the
|
|
// LICENSE file in the root directory of this source tree. An additional grant
|
|
// of patent rights can be found in the PATENTS file in the same directory.
|
|
#pragma once
|
|
|
|
#ifndef ROCKSDB_LITE
|
|
|
|
#include <string>
|
|
|
|
#include "rocksdb/db.h"
|
|
#include "rocksdb/iterator.h"
|
|
#include "rocksdb/options.h"
|
|
|
|
namespace rocksdb {
|
|
|
|
class DBImpl;
|
|
class Env;
|
|
struct SuperVersion;
|
|
class ColumnFamilyData;
|
|
|
|
/**
|
|
* TailingIterator is a special type of iterator that doesn't use an (implicit)
|
|
* snapshot. In other words, it can be used to read data that was added to the
|
|
* db after the iterator had been created.
|
|
*
|
|
* TailingIterator is optimized for sequential reading. It doesn't support
|
|
* Prev() and SeekToLast() operations.
|
|
*/
|
|
class TailingIterator : public Iterator {
|
|
public:
|
|
TailingIterator(Env* const env, DBImpl* db, const ReadOptions& read_options,
|
|
ColumnFamilyData* cfd);
|
|
virtual ~TailingIterator();
|
|
|
|
virtual bool Valid() const override;
|
|
virtual void SeekToFirst() override;
|
|
virtual void SeekToLast() override;
|
|
virtual void Seek(const Slice& target) override;
|
|
virtual void Next() override;
|
|
virtual void Prev() override;
|
|
virtual Slice key() const override;
|
|
virtual Slice value() const override;
|
|
virtual Status status() const override;
|
|
|
|
private:
|
|
void Cleanup();
|
|
|
|
Env* const env_;
|
|
DBImpl* const db_;
|
|
const ReadOptions read_options_;
|
|
ColumnFamilyData* const cfd_;
|
|
SuperVersion* super_version_;
|
|
|
|
// TailingIterator merges the contents of the two iterators below (one using
|
|
// mutable memtable contents only, other over SSTs and immutable memtables).
|
|
// See DBIter::GetTailingIteratorPair().
|
|
std::unique_ptr<Iterator> mutable_;
|
|
std::unique_ptr<Iterator> immutable_;
|
|
|
|
// points to either mutable_ or immutable_
|
|
Iterator* current_;
|
|
|
|
// key that precedes immutable iterator's current key
|
|
std::string prev_key_;
|
|
|
|
// unless prev_set is true, prev_key/prev_head is not valid and shouldn't be
|
|
// used; reset by createIterators()
|
|
bool is_prev_set_;
|
|
|
|
// prev_key_ was set by SeekImmutable(), which means that the interval of
|
|
// keys covered by immutable_ is [prev_key_, current], i.e. it includes the
|
|
// left endpoint
|
|
bool is_prev_inclusive_;
|
|
|
|
// internal iterator status
|
|
Status status_;
|
|
|
|
// check if this iterator's version matches DB's version
|
|
bool IsCurrentVersion() const;
|
|
|
|
// check if SeekImmutable() is needed due to target having a different prefix
|
|
// than prev_key_ (used when in prefix seek mode)
|
|
bool IsSamePrefix(const Slice& target) const;
|
|
|
|
// creates mutable_ and immutable_ iterators and updates version_number_
|
|
void CreateIterators();
|
|
|
|
// set current_ to be one of the iterators with the smallest key
|
|
void UpdateCurrent();
|
|
|
|
// seek on immutable_ and update prev_key
|
|
void SeekImmutable(const Slice& target);
|
|
};
|
|
|
|
} // namespace rocksdb
|
|
#endif // ROCKSDB_LITE
|