df9069d23f
Summary: In this patch, try to allocate the whole iterator tree starting from DBIter from an arena 1. ArenaWrappedDBIter is created when serves as the entry point of an iterator tree, with an arena in it. 2. Add an option to create iterator from arena for following iterators: DBIter, MergingIterator, MemtableIterator, all mem table's iterators, all table reader's iterators and two level iterator. 3. MergeIteratorBuilder is created to incrementally build the tree of internal iterators. It is passed to mem table list and version set and add iterators to it. Limitations: (1) Only DB::NewIterator() without tailing uses the arena. Other cases, including readonly DB and compactions are still from malloc (2) Two level iterator itself is allocated in arena, but not iterators inside it. Test Plan: make all check Reviewers: ljin, haobo Reviewed By: haobo Subscribers: leveldb, dhruba, yhchiang, igor Differential Revision: https://reviews.facebook.net/D18513
61 lines
1.9 KiB
C++
61 lines
1.9 KiB
C++
// 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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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include "rocksdb/types.h"
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namespace rocksdb {
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class Comparator;
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class Iterator;
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class Env;
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class Arena;
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// Return an iterator that provided the union of the data in
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// children[0,n-1]. Takes ownership of the child iterators and
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// will delete them when the result iterator is deleted.
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//
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// The result does no duplicate suppression. I.e., if a particular
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// key is present in K child iterators, it will be yielded K times.
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//
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// REQUIRES: n >= 0
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extern Iterator* NewMergingIterator(const Comparator* comparator,
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Iterator** children, int n,
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Arena* arena = nullptr);
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class MergingIterator;
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// A builder class to build a merging iterator by adding iterators one by one.
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class MergeIteratorBuilder {
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public:
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// comparator: the comparator used in merging comparator
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// arena: where the merging iterator needs to be allocated from.
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explicit MergeIteratorBuilder(const Comparator* comparator, Arena* arena);
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~MergeIteratorBuilder() {}
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// Add iter to the merging iterator.
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void AddIterator(Iterator* iter);
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// Get arena used to build the merging iterator. It is called one a child
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// iterator needs to be allocated.
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Arena* GetArena() { return arena; }
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// Return the result merging iterator.
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Iterator* Finish();
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private:
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MergingIterator* merge_iter;
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Iterator* first_iter;
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bool use_merging_iter;
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Arena* arena;
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};
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} // namespace rocksdb
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