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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 
[RocksDB] Reduce memory footprint of the blockbased table hash index.
 
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
Raw File
iter_heap.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.
//

#pragma once
#include <queue>

#include "rocksdb/comparator.h"
#include "table/iterator_wrapper.h"

namespace rocksdb {

// Return the max of two keys.
class MaxIteratorComparator {
 public:
  MaxIteratorComparator(const Comparator* comparator) :
    comparator_(comparator) {}

  bool operator()(IteratorWrapper* a, IteratorWrapper* b) {
    return comparator_->Compare(a->key(), b->key()) <= 0;
  }
 private:
  const Comparator* comparator_;
};

// Return the max of two keys.
class MinIteratorComparator {
 public:
  // if maxHeap is set comparator returns the max value.
  // else returns the min Value.
  // Can use to create a minHeap or a maxHeap.
  MinIteratorComparator(const Comparator* comparator) :
    comparator_(comparator) {}

  bool operator()(IteratorWrapper* a, IteratorWrapper* b) {
    return comparator_->Compare(a->key(), b->key()) > 0;
  }
 private:
  const Comparator* comparator_;
};

}  // namespace rocksdb
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