d719b095dc
Summary: While trying to reuse PinData() / ReleasePinnedData() .. to optimize away some memcpys I realized that there is a significant overhead for using PinData() / ReleasePinnedData if they were called many times. This diff refactor the pinning logic by introducing PinnedIteratorsManager a centralized component that will be created once and will be notified whenever we need to Pin an Iterator. This implementation have much less overhead than the original implementation Test Plan: make check -j64 COMPILE_WITH_ASAN=1 make check -j64 Reviewers: yhchiang, sdong, andrewkr Reviewed By: andrewkr Subscribers: andrewkr, dhruba Differential Revision: https://reviews.facebook.net/D56493
100 lines
3.7 KiB
C++
100 lines
3.7 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 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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// 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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// 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::ReleasePinnedIterators 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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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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