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 // This file demonstrates how to use the utility functions defined in
7 // rocksdb/utilities/options_util.h to open a rocksdb database without
8 // remembering all the rocksdb options.
9 #include <cstdio>
10 #include <string>
11 #include <vector>
12
13 #include "rocksdb/cache.h"
14 #include "rocksdb/compaction_filter.h"
15 #include "rocksdb/db.h"
16 #include "rocksdb/options.h"
17 #include "rocksdb/slice.h"
18 #include "rocksdb/table.h"
19 #include "rocksdb/utilities/options_util.h"
20
21 using namespace ROCKSDB_NAMESPACE;
22
23 #if defined(OS_WIN)
24 std::string kDBPath = "C:\\Windows\\TEMP\\rocksdb_options_file_example";
25 #else
26 std::string kDBPath = "/tmp/rocksdb_options_file_example";
27 #endif
28
29 namespace {
30 // A dummy compaction filter
31 class DummyCompactionFilter : public CompactionFilter {
32 public:
~DummyCompactionFilter()33 virtual ~DummyCompactionFilter() {}
Filter(int level,const Slice & key,const Slice & existing_value,std::string * new_value,bool * value_changed) const34 virtual bool Filter(int level, const Slice& key, const Slice& existing_value,
35 std::string* new_value, bool* value_changed) const {
36 return false;
37 }
Name() const38 virtual const char* Name() const { return "DummyCompactionFilter"; }
39 };
40
41 } // namespace
42
main()43 int main() {
44 DBOptions db_opt;
45 db_opt.create_if_missing = true;
46
47 std::vector<ColumnFamilyDescriptor> cf_descs;
48 cf_descs.push_back({kDefaultColumnFamilyName, ColumnFamilyOptions()});
49 cf_descs.push_back({"new_cf", ColumnFamilyOptions()});
50
51 // initialize BlockBasedTableOptions
52 auto cache = NewLRUCache(1 * 1024 * 1024 * 1024);
53 BlockBasedTableOptions bbt_opts;
54 bbt_opts.block_size = 32 * 1024;
55 bbt_opts.block_cache = cache;
56
57 // initialize column families options
58 std::unique_ptr<CompactionFilter> compaction_filter;
59 compaction_filter.reset(new DummyCompactionFilter());
60 cf_descs[0].options.table_factory.reset(NewBlockBasedTableFactory(bbt_opts));
61 cf_descs[0].options.compaction_filter = compaction_filter.get();
62 cf_descs[1].options.table_factory.reset(NewBlockBasedTableFactory(bbt_opts));
63
64 // destroy and open DB
65 DB* db;
66 Status s = DestroyDB(kDBPath, Options(db_opt, cf_descs[0].options));
67 assert(s.ok());
68 s = DB::Open(Options(db_opt, cf_descs[0].options), kDBPath, &db);
69 assert(s.ok());
70
71 // Create column family, and rocksdb will persist the options.
72 ColumnFamilyHandle* cf;
73 s = db->CreateColumnFamily(ColumnFamilyOptions(), "new_cf", &cf);
74 assert(s.ok());
75
76 // close DB
77 delete cf;
78 delete db;
79
80 // In the following code, we will reopen the rocksdb instance using
81 // the options file stored in the db directory.
82
83 // Load the options file.
84 DBOptions loaded_db_opt;
85 std::vector<ColumnFamilyDescriptor> loaded_cf_descs;
86 ConfigOptions config_options;
87 s = LoadLatestOptions(config_options, kDBPath, &loaded_db_opt,
88 &loaded_cf_descs);
89 assert(s.ok());
90 assert(loaded_db_opt.create_if_missing == db_opt.create_if_missing);
91
92 // Initialize pointer options for each column family
93 for (size_t i = 0; i < loaded_cf_descs.size(); ++i) {
94 auto* loaded_bbt_opt =
95 loaded_cf_descs[0]
96 .options.table_factory->GetOptions<BlockBasedTableOptions>();
97 // Expect the same as BlockBasedTableOptions will be loaded form file.
98 assert(loaded_bbt_opt->block_size == bbt_opts.block_size);
99 // However, block_cache needs to be manually initialized as documented
100 // in rocksdb/utilities/options_util.h.
101 loaded_bbt_opt->block_cache = cache;
102 }
103 // In addition, as pointer options are initialized with default value,
104 // we need to properly initialized all the pointer options if non-defalut
105 // values are used before calling DB::Open().
106 assert(loaded_cf_descs[0].options.compaction_filter == nullptr);
107 loaded_cf_descs[0].options.compaction_filter = compaction_filter.get();
108
109 // reopen the db using the loaded options.
110 std::vector<ColumnFamilyHandle*> handles;
111 s = DB::Open(loaded_db_opt, kDBPath, loaded_cf_descs, &handles, &db);
112 assert(s.ok());
113
114 // close DB
115 for (auto* handle : handles) {
116 delete handle;
117 }
118 delete db;
119 }
120