mirror of
https://github.com/facebook/rocksdb.git
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b555ed30a4
Summary: Use a customzied BlockBasedTableIterator and LevelIterator to replace current implementations leveraging two-level-iterator. Hope the customized logic will make code easier to understand. As a side effect, BlockBasedTableIterator reduces the allocation for the data block iterator object, and avoid the virtual function call to it, because we can directly reference BlockIter, a final class. Similarly, LevelIterator reduces virtual function call to the dummy iterator iterating the file metadata. It also enabled further optimization. The upper bound check is also moved from index block to data block. This implementation fits this iterator better. After the change, forwared iterator is slightly optimized to ensure we trim those iterators. The two-level-iterator now is only used by partitioned index, so it is simplified. Closes https://github.com/facebook/rocksdb/pull/3406 Differential Revision: D6809041 Pulled By: siying fbshipit-source-id: 7da3b9b1d3c8e9d9405302c15920af1fcaf50ffa
126 lines
4.5 KiB
C++
126 lines
4.5 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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#pragma once
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#include <string>
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#include "rocksdb/comparator.h"
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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 PinnedIteratorsManager;
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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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// Position at the first key in the source that at or before 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 before target.
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virtual void SeekForPrev(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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// True if the iterator is invalidated because it is out of the iterator
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// upper bound
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virtual bool IsOutOfBound() { return false; }
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// Pass the PinnedIteratorsManager to the Iterator, most Iterators dont
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// communicate with PinnedIteratorsManager so default implementation is no-op
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// but for Iterators that need to communicate with PinnedIteratorsManager
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// they will implement this function and use the passed pointer to communicate
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// with PinnedIteratorsManager.
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virtual void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) {}
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// If true, this means that the Slice returned by key() is valid as long as
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// PinnedIteratorsManager::ReleasePinnedData is not called and the
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// Iterator is not deleted.
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//
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// IsKeyPinned() is guaranteed to always return true if
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// - Iterator is created with ReadOptions::pin_data = true
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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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// If true, this means that the Slice returned by value() is valid as long as
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// PinnedIteratorsManager::ReleasePinnedData is not called and the
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// Iterator is not deleted.
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virtual bool IsValuePinned() 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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protected:
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void SeekForPrevImpl(const Slice& target, const Comparator* cmp) {
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Seek(target);
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if (!Valid()) {
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SeekToLast();
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}
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while (Valid() && cmp->Compare(target, key()) < 0) {
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Prev();
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}
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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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