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
main()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 }
84