ceph/src/rocksdb/table/block_based/partitioned_index_reader.h

   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 #include "table/block_based/index_reader_common.h"
  11 #include "util/hash_containers.h"
  12
  13 namespace ROCKSDB_NAMESPACE {
  14 // Index that allows binary search lookup in a two-level index structure.
  15 class PartitionIndexReader : public BlockBasedTable::IndexReaderCommon {
  16  public:
  17   // Read the partition index from the file and create an instance for
  18   // `PartitionIndexReader`.
  19   // On success, index_reader will be populated; otherwise it will remain
  20   // unmodified.
  21   static Status Create(const BlockBasedTable* table, const ReadOptions& ro,
  22                        FilePrefetchBuffer* prefetch_buffer, bool use_cache,
  23                        bool prefetch, bool pin,
  24                        BlockCacheLookupContext* lookup_context,
  25                        std::unique_ptr<IndexReader>* index_reader);
  26
  27   // return a two-level iterator: first level is on the partition index
  28   InternalIteratorBase<IndexValue>* NewIterator(
  29       const ReadOptions& read_options, bool /* disable_prefix_seek */,
  30       IndexBlockIter* iter, GetContext* get_context,
  31       BlockCacheLookupContext* lookup_context) override;
  32
  33   Status CacheDependencies(const ReadOptions& ro, bool pin) override;
  34   size_t ApproximateMemoryUsage() const override {
  35     size_t usage = ApproximateIndexBlockMemoryUsage();
  36 #ifdef ROCKSDB_MALLOC_USABLE_SIZE
  37     usage += malloc_usable_size(const_cast<PartitionIndexReader*>(this));
  38 #else
  39     usage += sizeof(*this);
  40 #endif  // ROCKSDB_MALLOC_USABLE_SIZE
  41     // TODO(myabandeh): more accurate estimate of partition_map_ mem usage
  42     return usage;
  43   }
  44
  45  private:
  46   PartitionIndexReader(const BlockBasedTable* t,
  47                        CachableEntry<Block>&& index_block)
  48       : IndexReaderCommon(t, std::move(index_block)) {}
  49
  50   // For partition blocks pinned in cache. This is expected to be "all or
  51   // none" so that !partition_map_.empty() can use an iterator expecting
  52   // all partitions to be saved here.
  53   UnorderedMap<uint64_t, CachableEntry<Block>> partition_map_;
  54 };
  55 }  // namespace ROCKSDB_NAMESPACE