1  // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
  2  // Use of this source code is governed by a BSD-style license that can be
  3  // found in the LICENSE file. See the AUTHORS file for names of contributors.
  4  
  5  #include "db/table_cache.h"
  6  
  7  #include "db/filename.h"
  8  #include "leveldb/env.h"
  9  #include "leveldb/table.h"
 10  #include "util/coding.h"
 11  
 12  namespace leveldb {
 13  
 14  struct TableAndFile {
 15    RandomAccessFile* file;
 16    Table* table;
 17  };
 18  
 19  static void DeleteEntry(const Slice& key, void* value) {
 20    TableAndFile* tf = reinterpret_cast<TableAndFile*>(value);
 21    delete tf->table;
 22    delete tf->file;
 23    delete tf;
 24  }
 25  
 26  static void UnrefEntry(void* arg1, void* arg2) {
 27    Cache* cache = reinterpret_cast<Cache*>(arg1);
 28    Cache::Handle* h = reinterpret_cast<Cache::Handle*>(arg2);
 29    cache->Release(h);
 30  }
 31  
 32  TableCache::TableCache(const std::string& dbname, const Options& options,
 33                         int entries)
 34      : env_(options.env),
 35        dbname_(dbname),
 36        options_(options),
 37        cache_(NewLRUCache(entries)) {}
 38  
 39  TableCache::~TableCache() { delete cache_; }
 40  
 41  Status TableCache::FindTable(uint64_t file_number, uint64_t file_size,
 42                               Cache::Handle** handle) {
 43    Status s;
 44    char buf[sizeof(file_number)];
 45    EncodeFixed64(buf, file_number);
 46    Slice key(buf, sizeof(buf));
 47    *handle = cache_->Lookup(key);
 48    if (*handle == nullptr) {
 49      std::string fname = TableFileName(dbname_, file_number);
 50      RandomAccessFile* file = nullptr;
 51      Table* table = nullptr;
 52      s = env_->NewRandomAccessFile(fname, &file);
 53      if (!s.ok()) {
 54        std::string old_fname = SSTTableFileName(dbname_, file_number);
 55        if (env_->NewRandomAccessFile(old_fname, &file).ok()) {
 56          s = Status::OK();
 57        }
 58      }
 59      if (s.ok()) {
 60        s = Table::Open(options_, file, file_size, &table);
 61      }
 62  
 63      if (!s.ok()) {
 64        assert(table == nullptr);
 65        delete file;
 66        // We do not cache error results so that if the error is transient,
 67        // or somebody repairs the file, we recover automatically.
 68      } else {
 69        TableAndFile* tf = new TableAndFile;
 70        tf->file = file;
 71        tf->table = table;
 72        *handle = cache_->Insert(key, tf, 1, &DeleteEntry);
 73      }
 74    }
 75    return s;
 76  }
 77  
 78  Iterator* TableCache::NewIterator(const ReadOptions& options,
 79                                    uint64_t file_number, uint64_t file_size,
 80                                    Table** tableptr) {
 81    if (tableptr != nullptr) {
 82      *tableptr = nullptr;
 83    }
 84  
 85    Cache::Handle* handle = nullptr;
 86    Status s = FindTable(file_number, file_size, &handle);
 87    if (!s.ok()) {
 88      return NewErrorIterator(s);
 89    }
 90  
 91    Table* table = reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table;
 92    Iterator* result = table->NewIterator(options);
 93    result->RegisterCleanup(&UnrefEntry, cache_, handle);
 94    if (tableptr != nullptr) {
 95      *tableptr = table;
 96    }
 97    return result;
 98  }
 99  
100  Status TableCache::Get(const ReadOptions& options, uint64_t file_number,
101                         uint64_t file_size, const Slice& k, void* arg,
102                         void (*handle_result)(void*, const Slice&,
103                                               const Slice&)) {
104    Cache::Handle* handle = nullptr;
105    Status s = FindTable(file_number, file_size, &handle);
106    if (s.ok()) {
107      Table* t = reinterpret_cast<TableAndFile*>(cache_->Value(handle))->table;
108      s = t->InternalGet(options, k, arg, handle_result);
109      cache_->Release(handle);
110    }
111    return s;
112  }
113  
114  void TableCache::Evict(uint64_t file_number) {
115    char buf[sizeof(file_number)];
116    EncodeFixed64(buf, file_number);
117    cache_->Erase(Slice(buf, sizeof(buf)));
118  }
119  
120  }  // namespace leveldb