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Revision df38c1ce660628f05b4686eeaf0b548295ce7967 authored by Mike Kolupaev on 22 April 2019, 15:17:45 UTC, committed by Facebook Github Bot on 22 April 2019, 15:20:35 UTC 
Add BlockBasedTableOptions::index_shortening (#5174)
 
Summary:
Introduce BlockBasedTableOptions::index_shortening to give users control on which key shortening techniques to be used in building index blocks. Before this patch, both separators and successor keys where shortened in indexes. With this patch, the default is set to kShortenSeparators to only shorten the separators. Since each index block has many separators and only one successor (last key), the change should not have negative impact on index block size. However it should prevent many unnecessary block loads where due to approximation introduced by shorted successor, seek would land us to the previous block and then fix it by moving to the next one.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5174

Differential Revision: D14884185

Pulled By: al13n321

fbshipit-source-id: 1b08bc8c03edcf09b6b8c16e9a7eea08ad4dd534
1 parent de76909
Raw File
memory_allocator.h 
//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).
//

#pragma once

#include "rocksdb/memory_allocator.h"

namespace rocksdb {

struct CustomDeleter {
  CustomDeleter(MemoryAllocator* a = nullptr) : allocator(a) {}

  void operator()(char* ptr) const {
    if (allocator) {
      allocator->Deallocate(reinterpret_cast<void*>(ptr));
    } else {
      delete[] ptr;
    }
  }

  MemoryAllocator* allocator;
};

using CacheAllocationPtr = std::unique_ptr<char[], CustomDeleter>;

inline CacheAllocationPtr AllocateBlock(size_t size,
                                        MemoryAllocator* allocator) {
  if (allocator) {
    auto block = reinterpret_cast<char*>(allocator->Allocate(size));
    return CacheAllocationPtr(block, allocator);
  }
  return CacheAllocationPtr(new char[size]);
}

}  // namespace rocksdb
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