mirror of https://github.com/facebook/rocksdb.git
114 lines
4.0 KiB
C++
114 lines
4.0 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// This file demonstrates how to use the utility functions defined in
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// rocksdb/utilities/options_util.h to open a rocksdb database without
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// remembering all the rocksdb options.
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#include <cstdio>
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#include <string>
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#include <vector>
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#include "rocksdb/cache.h"
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#include "rocksdb/compaction_filter.h"
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#include "rocksdb/db.h"
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#include "rocksdb/options.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/table.h"
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#include "rocksdb/utilities/options_util.h"
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using namespace rocksdb;
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std::string kDBPath = "/tmp/rocksdb_options_file_example";
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namespace {
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// A dummy compaction filter
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class DummyCompactionFilter : public CompactionFilter {
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public:
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virtual ~DummyCompactionFilter() {}
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virtual bool Filter(int level, const Slice& key, const Slice& existing_value,
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std::string* new_value, bool* value_changed) const {
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return false;
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}
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virtual const char* Name() const { return "DummyCompactionFilter"; }
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};
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} // namespace
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int main() {
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DBOptions db_opt;
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db_opt.create_if_missing = true;
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std::vector<ColumnFamilyDescriptor> cf_descs;
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cf_descs.push_back({kDefaultColumnFamilyName, ColumnFamilyOptions()});
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cf_descs.push_back({"new_cf", ColumnFamilyOptions()});
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// initialize BlockBasedTableOptions
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auto cache = NewLRUCache(1 * 1024 * 1024 * 1024);
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BlockBasedTableOptions bbt_opts;
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bbt_opts.block_size = 32 * 1024;
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bbt_opts.block_cache = cache;
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// initialize column families options
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std::unique_ptr<CompactionFilter> compaction_filter;
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compaction_filter.reset(new DummyCompactionFilter());
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cf_descs[0].options.table_factory.reset(NewBlockBasedTableFactory(bbt_opts));
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cf_descs[0].options.compaction_filter = compaction_filter.get();
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cf_descs[1].options.table_factory.reset(NewBlockBasedTableFactory(bbt_opts));
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// destroy and open DB
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DB* db;
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Status s = DestroyDB(kDBPath, Options(db_opt, cf_descs[0].options));
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assert(s.ok());
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s = DB::Open(Options(db_opt, cf_descs[0].options), kDBPath, &db);
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assert(s.ok());
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// Create column family, and rocksdb will persist the options.
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ColumnFamilyHandle* cf;
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s = db->CreateColumnFamily(ColumnFamilyOptions(), "new_cf", &cf);
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assert(s.ok());
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// close DB
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delete cf;
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delete db;
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// In the following code, we will reopen the rocksdb instance using
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// the options file stored in the db directory.
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// Load the options file.
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DBOptions loaded_db_opt;
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std::vector<ColumnFamilyDescriptor> loaded_cf_descs;
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s = LoadLatestOptions(kDBPath, Env::Default(), &loaded_db_opt,
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&loaded_cf_descs);
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assert(s.ok());
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assert(loaded_db_opt.create_if_missing == db_opt.create_if_missing);
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// Initialize pointer options for each column family
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for (size_t i = 0; i < loaded_cf_descs.size(); ++i) {
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auto* loaded_bbt_opt = reinterpret_cast<BlockBasedTableOptions*>(
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loaded_cf_descs[0].options.table_factory->GetOptions());
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// Expect the same as BlockBasedTableOptions will be loaded form file.
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assert(loaded_bbt_opt->block_size == bbt_opts.block_size);
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// However, block_cache needs to be manually initialized as documented
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// in rocksdb/utilities/options_util.h.
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loaded_bbt_opt->block_cache = cache;
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}
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// In addition, as pointer options are initialized with default value,
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// we need to properly initialized all the pointer options if non-defalut
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// values are used before calling DB::Open().
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assert(loaded_cf_descs[0].options.compaction_filter == nullptr);
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loaded_cf_descs[0].options.compaction_filter = compaction_filter.get();
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// reopen the db using the loaded options.
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std::vector<ColumnFamilyHandle*> handles;
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s = DB::Open(loaded_db_opt, kDBPath, loaded_cf_descs, &handles, &db);
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assert(s.ok());
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// close DB
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for (auto* handle : handles) {
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delete handle;
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}
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delete db;
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}
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