1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
2 //  This source code is licensed under both the GPLv2 (found in the
3 //  COPYING file in the root directory) and Apache 2.0 License
4 //  (found in the LICENSE.Apache file in the root directory).
5 //
6 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
7 // Use of this source code is governed by a BSD-style license that can be
8 // found in the LICENSE file. See the AUTHORS file for names of contributors.
9 #pragma once
10 
11 #include "table/block_based/index_reader_common.h"
12 
13 namespace ROCKSDB_NAMESPACE {
14 // Index that leverages an internal hash table to quicken the lookup for a given
15 // key.
16 class HashIndexReader : public BlockBasedTable::IndexReaderCommon {
17  public:
18   static Status Create(const BlockBasedTable* table,
19                        FilePrefetchBuffer* prefetch_buffer,
20                        InternalIterator* meta_index_iter, bool use_cache,
21                        bool prefetch, bool pin,
22                        BlockCacheLookupContext* lookup_context,
23                        std::unique_ptr<IndexReader>* index_reader);
24 
25   InternalIteratorBase<IndexValue>* NewIterator(
26       const ReadOptions& read_options, bool disable_prefix_seek,
27       IndexBlockIter* iter, GetContext* get_context,
28       BlockCacheLookupContext* lookup_context) override;
29 
ApproximateMemoryUsage()30   size_t ApproximateMemoryUsage() const override {
31     size_t usage = ApproximateIndexBlockMemoryUsage();
32 #ifdef ROCKSDB_MALLOC_USABLE_SIZE
33     usage += malloc_usable_size(const_cast<HashIndexReader*>(this));
34 #else
35     if (prefix_index_) {
36       usage += prefix_index_->ApproximateMemoryUsage();
37     }
38     usage += sizeof(*this);
39 #endif  // ROCKSDB_MALLOC_USABLE_SIZE
40     return usage;
41   }
42 
43  private:
HashIndexReader(const BlockBasedTable * t,CachableEntry<Block> && index_block)44   HashIndexReader(const BlockBasedTable* t, CachableEntry<Block>&& index_block)
45       : IndexReaderCommon(t, std::move(index_block)) {}
46 
47   std::unique_ptr<BlockPrefixIndex> prefix_index_;
48 };
49 }  // namespace ROCKSDB_NAMESPACE
50