e79ad9e184
Summary: We want to provide a way to detect whether an iterator is stale and needs to be recreated. Add a iterator property to return version number. Test Plan: Add two unit tests for it. Reviewers: IslamAbdelRahman, yhchiang, anthony, kradhakrishnan, andrewkr Reviewed By: andrewkr Subscribers: leveldb, dhruba Differential Revision: https://reviews.facebook.net/D54921
99 lines
3.6 KiB
C++
99 lines
3.6 KiB
C++
// Copyright (c) 2011-present, 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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//
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#pragma once
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#include <string>
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#include "rocksdb/iterator.h"
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#include "rocksdb/status.h"
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namespace rocksdb {
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class InternalIterator : public Cleanable {
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public:
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InternalIterator() {}
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virtual ~InternalIterator() {}
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// An iterator is either positioned at a key/value pair, or
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// not valid. This method returns true iff the iterator is valid.
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virtual bool Valid() const = 0;
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// Position at the first key in the source. The iterator is Valid()
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// after this call iff the source is not empty.
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virtual void SeekToFirst() = 0;
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// Position at the last key in the source. The iterator is
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// Valid() after this call iff the source is not empty.
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virtual void SeekToLast() = 0;
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// Position at the first key in the source that at or past target
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// The iterator is Valid() after this call iff the source contains
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// an entry that comes at or past target.
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virtual void Seek(const Slice& target) = 0;
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// Moves to the next entry in the source. After this call, Valid() is
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// true iff the iterator was not positioned at the last entry in the source.
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// REQUIRES: Valid()
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virtual void Next() = 0;
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// Moves to the previous entry in the source. After this call, Valid() is
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// true iff the iterator was not positioned at the first entry in source.
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// REQUIRES: Valid()
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virtual void Prev() = 0;
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// Return the key for the current entry. The underlying storage for
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// the returned slice is valid only until the next modification of
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// the iterator.
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// REQUIRES: Valid()
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virtual Slice key() const = 0;
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// Return the value for the current entry. The underlying storage for
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// the returned slice is valid only until the next modification of
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// the iterator.
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// REQUIRES: !AtEnd() && !AtStart()
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virtual Slice value() const = 0;
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// If an error has occurred, return it. Else return an ok status.
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// If non-blocking IO is requested and this operation cannot be
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// satisfied without doing some IO, then this returns Status::Incomplete().
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virtual Status status() const = 0;
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// Make sure that all current and future data blocks used by this iterator
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// will be pinned in memory and will not be released except when
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// ReleasePinnedData() is called or the iterator is deleted.
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virtual Status PinData() { return Status::NotSupported(""); }
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// Release all blocks that were pinned because of PinData() and no future
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// blocks will be pinned.
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virtual Status ReleasePinnedData() { return Status::NotSupported(""); }
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// If true, this means that the Slice returned by key() is valid as long
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// as the iterator is not deleted and ReleasePinnedData() is not called.
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//
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// IsKeyPinned() is guaranteed to always return true if
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// - PinData() is called
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// - DB tables were created with BlockBasedTableOptions::use_delta_encoding
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// set to false.
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virtual bool IsKeyPinned() const { return false; }
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virtual Status GetProperty(std::string prop_name, std::string* prop) {
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return Status::NotSupported("");
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}
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private:
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// No copying allowed
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InternalIterator(const InternalIterator&) = delete;
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InternalIterator& operator=(const InternalIterator&) = delete;
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};
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// Return an empty iterator (yields nothing).
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extern InternalIterator* NewEmptyInternalIterator();
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// Return an empty iterator with the specified status.
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extern InternalIterator* NewErrorInternalIterator(const Status& status);
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} // namespace rocksdb
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