Revision 0f0076ed5abd1540dd0b7af5d51cde529c178d52 authored by Haobo Xu on 13 June 2014, 02:03:22 UTC, committed by Haobo Xu on 19 June 2014, 01:16:07 UTC
Summary: Currently, the in-memory hash index of blockbased table uses a precise hash map to track the prefix to block range mapping. In some use cases, especially when prefix itself is big, the memory overhead becomes a problem. This diff introduces a fixed hash bucket array that does not store the prefix and allows prefix collision, which is similar to the plaintable hash index, in order to reduce the memory consumption. Just a quick draft, still testing and refining. Test Plan: unit test and shadow testing Reviewers: dhruba, kailiu, sdong Reviewed By: sdong Subscribers: leveldb Differential Revision: https://reviews.facebook.net/D19047
1 parent 3525aac
merger.h
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include "rocksdb/types.h"
namespace rocksdb {
class Comparator;
class Iterator;
class Env;
class Arena;
// Return an iterator that provided the union of the data in
// children[0,n-1]. Takes ownership of the child iterators and
// will delete them when the result iterator is deleted.
//
// The result does no duplicate suppression. I.e., if a particular
// key is present in K child iterators, it will be yielded K times.
//
// REQUIRES: n >= 0
extern Iterator* NewMergingIterator(const Comparator* comparator,
Iterator** children, int n,
Arena* arena = nullptr);
class MergingIterator;
// A builder class to build a merging iterator by adding iterators one by one.
class MergeIteratorBuilder {
public:
// comparator: the comparator used in merging comparator
// arena: where the merging iterator needs to be allocated from.
explicit MergeIteratorBuilder(const Comparator* comparator, Arena* arena);
~MergeIteratorBuilder() {}
// Add iter to the merging iterator.
void AddIterator(Iterator* iter);
// Get arena used to build the merging iterator. It is called one a child
// iterator needs to be allocated.
Arena* GetArena() { return arena; }
// Return the result merging iterator.
Iterator* Finish();
private:
MergingIterator* merge_iter;
Iterator* first_iter;
bool use_merging_iter;
Arena* arena;
};
} // namespace rocksdb
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