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 std::string kDBPath = "/tmp/rocksdb_options_file_example";
24
25 namespace {
26 // A dummy compaction filter
27 class DummyCompactionFilter : public CompactionFilter {
28 public:
~DummyCompactionFilter()29 virtual ~DummyCompactionFilter() {}
Filter(int level,const Slice & key,const Slice & existing_value,std::string * new_value,bool * value_changed) const30 virtual bool Filter(int level, const Slice& key, const Slice& existing_value,
31 std::string* new_value, bool* value_changed) const {
32 return false;
33 }
Name() const34 virtual const char* Name() const { return "DummyCompactionFilter"; }
35 };
36
37 } // namespace
38
main()39 int main() {
40 DBOptions db_opt;
41 db_opt.create_if_missing = true;
42
43 std::vector<ColumnFamilyDescriptor> cf_descs;
44 cf_descs.push_back({kDefaultColumnFamilyName, ColumnFamilyOptions()});
45 cf_descs.push_back({"new_cf", ColumnFamilyOptions()});
46
47 // initialize BlockBasedTableOptions
48 auto cache = NewLRUCache(1 * 1024 * 1024 * 1024);
49 BlockBasedTableOptions bbt_opts;
50 bbt_opts.block_size = 32 * 1024;
51 bbt_opts.block_cache = cache;
52
53 // initialize column families options
54 std::unique_ptr<CompactionFilter> compaction_filter;
55 compaction_filter.reset(new DummyCompactionFilter());
56 cf_descs[0].options.table_factory.reset(NewBlockBasedTableFactory(bbt_opts));
57 cf_descs[0].options.compaction_filter = compaction_filter.get();
58 cf_descs[1].options.table_factory.reset(NewBlockBasedTableFactory(bbt_opts));
59
60 // destroy and open DB
61 DB* db;
62 Status s = DestroyDB(kDBPath, Options(db_opt, cf_descs[0].options));
63 assert(s.ok());
64 s = DB::Open(Options(db_opt, cf_descs[0].options), kDBPath, &db);
65 assert(s.ok());
66
67 // Create column family, and rocksdb will persist the options.
68 ColumnFamilyHandle* cf;
69 s = db->CreateColumnFamily(ColumnFamilyOptions(), "new_cf", &cf);
70 assert(s.ok());
71
72 // close DB
73 delete cf;
74 delete db;
75
76 // In the following code, we will reopen the rocksdb instance using
77 // the options file stored in the db directory.
78
79 // Load the options file.
80 DBOptions loaded_db_opt;
81 std::vector<ColumnFamilyDescriptor> loaded_cf_descs;
82 s = LoadLatestOptions(kDBPath, Env::Default(), &loaded_db_opt,
83 &loaded_cf_descs);
84 assert(s.ok());
85 assert(loaded_db_opt.create_if_missing == db_opt.create_if_missing);
86
87 // Initialize pointer options for each column family
88 for (size_t i = 0; i < loaded_cf_descs.size(); ++i) {
89 auto* loaded_bbt_opt = reinterpret_cast<BlockBasedTableOptions*>(
90 loaded_cf_descs[0].options.table_factory->GetOptions());
91 // Expect the same as BlockBasedTableOptions will be loaded form file.
92 assert(loaded_bbt_opt->block_size == bbt_opts.block_size);
93 // However, block_cache needs to be manually initialized as documented
94 // in rocksdb/utilities/options_util.h.
95 loaded_bbt_opt->block_cache = cache;
96 }
97 // In addition, as pointer options are initialized with default value,
98 // we need to properly initialized all the pointer options if non-defalut
99 // values are used before calling DB::Open().
100 assert(loaded_cf_descs[0].options.compaction_filter == nullptr);
101 loaded_cf_descs[0].options.compaction_filter = compaction_filter.get();
102
103 // reopen the db using the loaded options.
104 std::vector<ColumnFamilyHandle*> handles;
105 s = DB::Open(loaded_db_opt, kDBPath, loaded_cf_descs, &handles, &db);
106 assert(s.ok());
107
108 // close DB
109 for (auto* handle : handles) {
110 delete handle;
111 }
112 delete db;
113 }
114