mirror of https://github.com/facebook/rocksdb.git
84 lines
2.4 KiB
C++
84 lines
2.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#include <cstdio>
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#include <string>
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#include "rocksdb/db.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/options.h"
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using namespace rocksdb;
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std::string kDBPath = "/tmp/rocksdb_simple_example";
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int main() {
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DB* db;
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Options options;
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// Optimize RocksDB. This is the easiest way to get RocksDB to perform well
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options.IncreaseParallelism();
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options.OptimizeLevelStyleCompaction();
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// create the DB if it's not already present
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options.create_if_missing = true;
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// open DB
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Status s = DB::Open(options, kDBPath, &db);
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assert(s.ok());
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// Put key-value
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s = db->Put(WriteOptions(), "key1", "value");
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assert(s.ok());
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std::string value;
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// get value
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s = db->Get(ReadOptions(), "key1", &value);
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assert(s.ok());
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assert(value == "value");
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// atomically apply a set of updates
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{
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WriteBatch batch;
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batch.Delete("key1");
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batch.Put("key2", value);
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s = db->Write(WriteOptions(), &batch);
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}
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s = db->Get(ReadOptions(), "key1", &value);
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assert(s.IsNotFound());
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db->Get(ReadOptions(), "key2", &value);
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assert(value == "value");
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{
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PinnableSlice pinnable_val;
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db->Get(ReadOptions(), db->DefaultColumnFamily(), "key2", &pinnable_val);
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assert(pinnable_val == "value");
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}
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{
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std::string string_val;
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// If it cannot pin the value, it copies the value to its internal buffer.
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// The intenral buffer could be set during construction.
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PinnableSlice pinnable_val(&string_val);
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db->Get(ReadOptions(), db->DefaultColumnFamily(), "key2", &pinnable_val);
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assert(pinnable_val == "value");
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// If the value is not pinned, the internal buffer must have the value.
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assert(pinnable_val.IsPinned() || string_val == "value");
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}
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PinnableSlice pinnable_val;
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db->Get(ReadOptions(), db->DefaultColumnFamily(), "key1", &pinnable_val);
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assert(s.IsNotFound());
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// Reset PinnableSlice after each use and before each reuse
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pinnable_val.Reset();
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db->Get(ReadOptions(), db->DefaultColumnFamily(), "key2", &pinnable_val);
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assert(pinnable_val == "value");
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pinnable_val.Reset();
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// The Slice pointed by pinnable_val is not valid after this point
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delete db;
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return 0;
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}
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