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rocksdb/db/forward_iterator.h

131 lines
4.1 KiB

// 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 <vector>
#include <queue>
#include "rocksdb/db.h"
#include "rocksdb/iterator.h"
#include "rocksdb/options.h"
#include "db/dbformat.h"
#include "util/arena.h"
namespace rocksdb {
class DBImpl;
class Env;
struct SuperVersion;
class ColumnFamilyData;
class LevelIterator;
struct FileMetaData;
class MinIterComparator {
public:
explicit MinIterComparator(const Comparator* comparator) :
comparator_(comparator) {}
bool operator()(Iterator* a, Iterator* b) {
return comparator_->Compare(a->key(), b->key()) > 0;
}
private:
const Comparator* comparator_;
};
typedef std::priority_queue<Iterator*,
std::vector<Iterator*>,
MinIterComparator> MinIterHeap;
/**
* ForwardIterator is a special type of iterator that only supports Seek()
* and Next(). It is expected to perform better than TailingIterator by
* removing the encapsulation and making all information accessible within
* the iterator. At the current implementation, snapshot is taken at the
* time Seek() is called. The Next() followed do not see new values after.
*/
class ForwardIterator : public Iterator {
public:
ForwardIterator(DBImpl* db, const ReadOptions& read_options,
ColumnFamilyData* cfd, SuperVersion* current_sv = nullptr);
virtual ~ForwardIterator();
void SeekToLast() override {
status_ = Status::NotSupported("ForwardIterator::SeekToLast()");
valid_ = false;
}
void Prev() override {
status_ = Status::NotSupported("ForwardIterator::Prev");
valid_ = false;
}
virtual bool Valid() const override;
void SeekToFirst() override;
virtual void Seek(const Slice& target) override;
virtual void Next() override;
virtual Slice key() const override;
virtual Slice value() const override;
virtual Status status() const override;
bool TEST_CheckDeletedIters();
private:
void Cleanup(bool release_sv);
void RebuildIterators(bool refresh_sv);
void ResetIncompleteIterators();
void SeekInternal(const Slice& internal_key, bool seek_to_first);
void UpdateCurrent();
bool NeedToSeekImmutable(const Slice& internal_key);
void DeleteCurrentIter();
uint32_t FindFileInRange(
const std::vector<FileMetaData*>& files, const Slice& internal_key,
uint32_t left, uint32_t right);
bool IsOverUpperBound(const Slice& internal_key) const;
DBImpl* const db_;
const ReadOptions read_options_;
ColumnFamilyData* const cfd_;
const SliceTransform* const prefix_extractor_;
const Comparator* user_comparator_;
MinIterHeap immutable_min_heap_;
SuperVersion* sv_;
Iterator* mutable_iter_;
std::vector<Iterator*> imm_iters_;
std::vector<Iterator*> l0_iters_;
std::vector<LevelIterator*> level_iters_;
Iterator* current_;
bool valid_;
// Internal iterator status; set only by one of the unsupported methods.
Status status_;
// Status of immutable iterators, maintained here to avoid iterating over
// all of them in status().
Status immutable_status_;
// Indicates that at least one of the immutable iterators pointed to a key
// larger than iterate_upper_bound and was therefore destroyed. Seek() may
// need to rebuild such iterators.
bool has_iter_trimmed_for_upper_bound_;
// Is current key larger than iterate_upper_bound? If so, makes Valid()
// return false.
bool current_over_upper_bound_;
// Left endpoint of the range of keys that immutable iterators currently
// cover. When Seek() is called with a key that's within that range, immutable
// iterators don't need to be moved; see NeedToSeekImmutable(). This key is
// included in the range after a Seek(), but excluded when advancing the
// iterator using Next().
IterKey prev_key_;
bool is_prev_set_;
bool is_prev_inclusive_;
Arena arena_;
};
} // namespace rocksdb
#endif // ROCKSDB_LITE