rocksdb/table/internal_iterator.h
Andrew Kryczka 5d68243e61 Comment out unused variables
Summary:
Submitting on behalf of another employee.
Closes https://github.com/facebook/rocksdb/pull/3557

Differential Revision: D7146025

Pulled By: ajkr

fbshipit-source-id: 495ca5db5beec3789e671e26f78170957704e77e
2018-03-05 13:13:41 -08:00

127 lines
4.5 KiB
C++

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
#pragma once
#include <string>
#include "rocksdb/comparator.h"
#include "rocksdb/iterator.h"
#include "rocksdb/status.h"
namespace rocksdb {
class PinnedIteratorsManager;
class InternalIterator : public Cleanable {
public:
InternalIterator() {}
virtual ~InternalIterator() {}
// An iterator is either positioned at a key/value pair, or
// not valid. This method returns true iff the iterator is valid.
virtual bool Valid() const = 0;
// Position at the first key in the source. The iterator is Valid()
// after this call iff the source is not empty.
virtual void SeekToFirst() = 0;
// Position at the last key in the source. The iterator is
// Valid() after this call iff the source is not empty.
virtual void SeekToLast() = 0;
// Position at the first key in the source that at or past target
// The iterator is Valid() after this call iff the source contains
// an entry that comes at or past target.
virtual void Seek(const Slice& target) = 0;
// Position at the first key in the source that at or before target
// The iterator is Valid() after this call iff the source contains
// an entry that comes at or before target.
virtual void SeekForPrev(const Slice& target) = 0;
// Moves to the next entry in the source. After this call, Valid() is
// true iff the iterator was not positioned at the last entry in the source.
// REQUIRES: Valid()
virtual void Next() = 0;
// Moves to the previous entry in the source. After this call, Valid() is
// true iff the iterator was not positioned at the first entry in source.
// REQUIRES: Valid()
virtual void Prev() = 0;
// Return the key for the current entry. The underlying storage for
// the returned slice is valid only until the next modification of
// the iterator.
// REQUIRES: Valid()
virtual Slice key() const = 0;
// Return the value for the current entry. The underlying storage for
// the returned slice is valid only until the next modification of
// the iterator.
// REQUIRES: !AtEnd() && !AtStart()
virtual Slice value() const = 0;
// If an error has occurred, return it. Else return an ok status.
// If non-blocking IO is requested and this operation cannot be
// satisfied without doing some IO, then this returns Status::Incomplete().
virtual Status status() const = 0;
// True if the iterator is invalidated because it is out of the iterator
// upper bound
virtual bool IsOutOfBound() { return false; }
// Pass the PinnedIteratorsManager to the Iterator, most Iterators dont
// communicate with PinnedIteratorsManager so default implementation is no-op
// but for Iterators that need to communicate with PinnedIteratorsManager
// they will implement this function and use the passed pointer to communicate
// with PinnedIteratorsManager.
virtual void SetPinnedItersMgr(PinnedIteratorsManager* /*pinned_iters_mgr*/) {
}
// If true, this means that the Slice returned by key() is valid as long as
// PinnedIteratorsManager::ReleasePinnedData is not called and the
// Iterator is not deleted.
//
// IsKeyPinned() is guaranteed to always return true if
// - Iterator is created with ReadOptions::pin_data = true
// - DB tables were created with BlockBasedTableOptions::use_delta_encoding
// set to false.
virtual bool IsKeyPinned() const { return false; }
// If true, this means that the Slice returned by value() is valid as long as
// PinnedIteratorsManager::ReleasePinnedData is not called and the
// Iterator is not deleted.
virtual bool IsValuePinned() const { return false; }
virtual Status GetProperty(std::string /*prop_name*/, std::string* /*prop*/) {
return Status::NotSupported("");
}
protected:
void SeekForPrevImpl(const Slice& target, const Comparator* cmp) {
Seek(target);
if (!Valid()) {
SeekToLast();
}
while (Valid() && cmp->Compare(target, key()) < 0) {
Prev();
}
}
private:
// No copying allowed
InternalIterator(const InternalIterator&) = delete;
InternalIterator& operator=(const InternalIterator&) = delete;
};
// Return an empty iterator (yields nothing).
extern InternalIterator* NewEmptyInternalIterator();
// Return an empty iterator with the specified status.
extern InternalIterator* NewErrorInternalIterator(const Status& status);
} // namespace rocksdb