ceph/src/rocksdb/examples/simple_example.cc

   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 #include <cstdio>
   7 #include <string>
   8
   9 #include "rocksdb/db.h"
  10 #include "rocksdb/slice.h"
  11 #include "rocksdb/options.h"
  12
  13 using namespace ROCKSDB_NAMESPACE;
  14
  15 std::string kDBPath = "/tmp/rocksdb_simple_example";
  16
  17 int main() {
  18   DB* db;
  19   Options options;
  20   // Optimize RocksDB. This is the easiest way to get RocksDB to perform well
  21   options.IncreaseParallelism();
  22   options.OptimizeLevelStyleCompaction();
  23   // create the DB if it's not already present
  24   options.create_if_missing = true;
  25
  26   // open DB
  27   Status s = DB::Open(options, kDBPath, &db);
  28   assert(s.ok());
  29
  30   // Put key-value
  31   s = db->Put(WriteOptions(), "key1", "value");
  32   assert(s.ok());
  33   std::string value;
  34   // get value
  35   s = db->Get(ReadOptions(), "key1", &value);
  36   assert(s.ok());
  37   assert(value == "value");
  38
  39   // atomically apply a set of updates
  40   {
  41     WriteBatch batch;
  42     batch.Delete("key1");
  43     batch.Put("key2", value);
  44     s = db->Write(WriteOptions(), &batch);
  45   }
  46
  47   s = db->Get(ReadOptions(), "key1", &value);
  48   assert(s.IsNotFound());
  49
  50   db->Get(ReadOptions(), "key2", &value);
  51   assert(value == "value");
  52
  53   {
  54     PinnableSlice pinnable_val;
  55     db->Get(ReadOptions(), db->DefaultColumnFamily(), "key2", &pinnable_val);
  56     assert(pinnable_val == "value");
  57   }
  58
  59   {
  60     std::string string_val;
  61     // If it cannot pin the value, it copies the value to its internal buffer.
  62     // The intenral buffer could be set during construction.
  63     PinnableSlice pinnable_val(&string_val);
  64     db->Get(ReadOptions(), db->DefaultColumnFamily(), "key2", &pinnable_val);
  65     assert(pinnable_val == "value");
  66     // If the value is not pinned, the internal buffer must have the value.
  67     assert(pinnable_val.IsPinned() || string_val == "value");
  68   }
  69
  70   PinnableSlice pinnable_val;
  71   db->Get(ReadOptions(), db->DefaultColumnFamily(), "key1", &pinnable_val);
  72   assert(s.IsNotFound());
  73   // Reset PinnableSlice after each use and before each reuse
  74   pinnable_val.Reset();
  75   db->Get(ReadOptions(), db->DefaultColumnFamily(), "key2", &pinnable_val);
  76   assert(pinnable_val == "value");
  77   pinnable_val.Reset();
  78   // The Slice pointed by pinnable_val is not valid after this point
  79
  80   delete db;
  81
  82   return 0;
  83 }