mirror of https://github.com/facebook/rocksdb.git
85 lines
2.4 KiB
C
85 lines
2.4 KiB
C
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// Copyright (c) 2013, 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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#pragma once
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#ifndef ROCKSDB_LITE
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#include <mutex>
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#include <queue>
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#include <string>
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#include <vector>
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#include "db/column_family.h"
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#include "rocksdb/db.h"
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#include "rocksdb/iterator.h"
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#include "rocksdb/options.h"
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#include "util/arena.h"
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namespace rocksdb {
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class DBImpl;
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struct SuperVersion;
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class ColumnFamilyData;
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/**
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* ManagedIterator is a special type of iterator that supports freeing the
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* underlying iterator and still being able to access the current key/value
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* pair. This is done by copying the key/value pair so that clients can
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* continue to access the data without getting a SIGSEGV.
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* The underlying iterator can be freed manually through the call to
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* ReleaseIter or automatically (as needed on space pressure or age.)
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* The iterator is recreated using the saved original arguments.
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*/
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class ManagedIterator : public Iterator {
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public:
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ManagedIterator(DBImpl* db, const ReadOptions& read_options,
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ColumnFamilyData* cfd);
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virtual ~ManagedIterator();
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virtual void SeekToLast() override;
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virtual void Prev() override;
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virtual bool Valid() const override;
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void SeekToFirst() override;
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virtual void Seek(const Slice& target) override;
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virtual void Next() override;
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virtual Slice key() const override;
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virtual Slice value() const override;
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virtual Status status() const override;
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void ReleaseIter(bool only_old);
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void SetDropOld(bool only_old) {
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only_drop_old_ = read_options_.tailing || only_old;
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}
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private:
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void RebuildIterator();
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void UpdateCurrent();
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void SeekInternal(const Slice& user_key, bool seek_to_first);
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bool NeedToRebuild();
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void Lock();
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bool TryLock();
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void UnLock();
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DBImpl* const db_;
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ReadOptions read_options_;
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ColumnFamilyData* const cfd_;
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ColumnFamilyHandleInternal cfh_;
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uint64_t svnum_;
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std::unique_ptr<Iterator> mutable_iter_;
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// internal iterator status
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Status status_;
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bool valid_;
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IterKey cached_key_;
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IterKey cached_value_;
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bool only_drop_old_ = true;
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bool snapshot_created_;
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bool release_supported_;
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std::mutex in_use_; // is managed iterator in use
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};
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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