rocksDB is an embeddable , persistent key-value store.
The following introduction comes from rocksDB Chinese official website
https://rocksdb.org.cn/
It has the following four characteristics
1 High performance: RocksDB uses a set of log structure database engines. For better performance, this engine is written in C++. Key and value are byte streams of any size.
2 Optimized for fast storage: RocksDB is specially optimized for fast and low-latency storage devices (such as flash memory or high-speed hard disk). RocksDB will maximize the high-rate read and write performance of flash memory and RAM.
3Adapability: RocksDB is suitable for many different types of workloads. From data storage engines like MyRocks, to application data caching, and even some embedded workloads, RocksDB can calmly face these different data workload needs.
4 Basic and Advanced Database Operations RocksDB provides some basic operations, such as opening and closing the database. Read and write support is also provided for advanced operations such as merging and compression filtering.
RockDB installation and use
There are several ways to install rocksDB. Since the official does not provide a binary library for the corresponding platform, it needs to be compiled and used by itself.
RocksDB installation is very simple, but you need to change your view on rocksDB. It is not a heavyweight database, it is an embedded key-value store. This means that you can try it yourself in the development environment by simply adding rocksDB dependencies to your Maven project. If you don't understand this, you may go to the following two unrecommended installation methods.
Once you check the official website of rocksDB, you will find that you need to write a C++ program (not recommended)
#include <assert>#include "rocksdb/db.h"rocksdb::DB* db;rocksdb::Options options;options.create_if_missing = true;rocksdb::Status status = rocksdb::DB::Open(options, "/tmp/testdb", &db);assert(status.ok());
Create a database? ? ? ? Why is it different from the mysql or mongo you used before? Why doesn't there be a script like start.sh or start.bat? Do you want me to write? After writing, I found that I didn’t know how to associate it with the rocksDB library. What to do? I forgot about C++.
Method 2 uses pyrocksDB (not recommended)
http://pyrocksdb.readthedocs.io/en/latest/installation.html
For detailed installation documents, please refer to the official website installation documents of pyrocksDB.
The above two methods are more friendly to developers who are familiar with C++ or python, but not very friendly to Java developers.
Next, let’s introduce the third method.
Method 3 Use maven (recommended)
Create a new maven project and modify the pom.xml dependency to add it
<dependency> <groupId>org.rocksdb</groupId> <artifactId>rocksdbjni</artifactId> <version>5.8.6</version></dependency>
You can choose the version you like.
Then, the language level of maven is higher, and I set it globally to 1.8 here
<profiles> <profile> <id>jdk18</id> <activation> <activeByDefault>true</activeByDefault> <jdk>1.8</jdk> </activation> <properties> <maven.compiler.source>1.8</maven.compiler.source> <maven.compiler.target>1.8</maven.compiler.target> <maven.compiler.compilerVersion>1.8</maven.compiler.compilerVersion> </properties> </profile></profiles>
At this point, the environment is ready. Have you returned to the familiar Java world?
Then, modify the running configuration in the IDE, add a program to the database storage path, and then run the test. I will give this class at the end of the article.
There will be log output when running the console, and a new file will also appear in the file.
We will update more about the rockDB development API and its applications in production later. I hope everyone will pay attention to it.
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.// This source code is licensed under both the GPLv2 (found in the// COPYING file in the root directory) and Apache 2.0 License// (found in the LICENSE.Apache file in the root directory).import org.rocksdb.*;import org.rocksdb.util.SizeUnit;import java.util.ArrayList;import java.util.Arrays;import java.util.List;import java.util.Map;public class RocksDBSample { static { RocksDB.loadLibrary(); } public static void main(final String[] args) { if (args.length < 1) { System.out.println("usage: RocksDBSample db_path"); System.exit(-1); } final String db_path = args[0]; final String db_path_not_found = db_path + "_not_found"; System.out.println("RocksDBSample"); try (final Options options = new Options(); final Filter bloomFilter = new BloomFilter(10); final ReadOptions readOptions = new ReadOptions() .setFillCache(false); final Statistics stats = new Statistics(); final RateLimiter rateLimiter = new RateLimiter(100000000,10000, 10)) { try (final RocksDB db = RocksDB.open(options, db_path_not_found)) { assert (false); } catch (final RocksDBException e) { System.out.format("Caught the expected exception -- %s/n", e); } try { options.setCreateIfMissing(true) .setStatistics(stats) .setWriteBufferSize(8 * SizeUnit.KB) .setMaxWriteBufferNumber(3) .setMaxBackgroundCompactions(10) .setCompressionType(CompressionType.SNAPPY_COMPRESSION) .setCompactionStyle(CompactionStyle.UNIVERSAL); } catch (final IllegalArgumentException e) { assert (false); } assert (options.createIfMissing() == true); assert (options.writeBufferSize() == 8 * SizeUnit.KB); assert (options.maxWriteBufferNumber() == 3); assert (options.maxBackgroundCompactions() == 10); assert (options.compressionType() == CompressionType.SNAPPY_COMPRESSION); assert (options.compactionStyle() == CompactionStyle.UNIVERSAL); assert (options.memTableFactoryName().equals("SkipListFactory")); options.setMemTableConfig( new HashSkipListMemTableConfig() .setHeight(4) .setBranchingFactor(4) .setBucketCount(2000000)); assert (options.memTableFactoryName().equals("HashSkipListRepFactory")); options.setMemTableConfig( new HashLinkedListMemTableConfig() .setBucketCount(100000)); assert (options.memTableFactoryName().equals("HashLinkedListRepFactory")); options.setMemTableConfig( new VectorMemTableConfig().setReservedSize(10000)); assert (options.memTableFactoryName().equals("VectorRepFactory")); options.setMemTableConfig(new SkipListMemTableConfig()); assert (options.memTableFactoryName().equals("SkipListFactory")); options.setTableFormatConfig(new PlainTableConfig()); // Plain-Table requires mmap read options.setAllowMmapReads(true); assert (options.tableFactoryName().equals("PlainTable")); options.setRateLimiter(rateLimiter); final BlockBasedTableConfig table_options = new BlockBasedTableConfig(); table_options.setBlockCacheSize(64 * SizeUnit.KB) .setFilter(bloomFilter) .setCacheNumShardBits(6) .setBlockSizeDeviation(5) .setBlockRestartInterval(10) .setCacheIndexAndFilterBlocks(true) .setHashIndexAllowCollision(false) .setBlockCacheCompressedSize(64 * SizeUnit.KB) .setBlockCacheCompressedNumShardBits(10); assert (table_options.blockCacheSize() == 64 * SizeUnit.KB); assert (table_options.cacheNumShardBits() == 6); assert (table_options.blockSizeDeviation() == 5); assert (table_options.blockRestartInterval() == 10); assert (table_options.cacheIndexAndFilterBlocks() == true); assert (table_options.hashIndexAllowCollision() == false); assert (table_options.blockCacheCompressedSize() == 64 * SizeUnit.KB); assert (table_options.blockCacheCompressedNumShardBits() == 10); options.setTableFormatConfig(table_options); assert (options.tableFactoryName().equals("BlockBasedTable")); try (final RocksDB db = RocksDB.open(options, db_path)) { db.put("hello".getBytes(), "world".getBytes()); final byte[] value = db.get("hello".getBytes()); assert ("world".equals(new String(value))); final String str = db.getProperty("rocksdb.stats"); assert (str != null && !str.equals("")); } catch (final RocksDBException e) { System.out.format("[ERROR] caught the unexpected exception -- %s/n", e); assert (false); } try (final RocksDB db = RocksDB.open(options, db_path)) { db.put("hello".getBytes(), "world".getBytes()); byte[] value = db.get("hello".getBytes()); System.out.format("Get('hello') = %s/n", new String(value)); for (int i = 1; i <= 9; ++i) { for (int j = 1; j <= 9; ++j) { db.put(String.format("%dx%d", i, j).getBytes(), String.format("%d", i * j).getBytes()); } } for (int i = 1; i <= 9; ++i) { for (int j = 1; j <= 9; ++j) { System.out.format("%s", new String(db.get( String.format("%dx%d", i, j).getBytes()))); } System.out.println(""); } // write batch test try (final WriteOptions writeOpt = new WriteOptions()) { for (int i = 10; i <= 19; ++i) { try (final WriteBatch batch = new WriteBatch()) { for (int j = 10; j <= 19; ++j) { batch.put(String.format("%dx%d", i, j).getBytes(), String.format("%d", i * j).getBytes()); } db.write(writeOpt, batch); } } } for (int i = 10; i <= 19; ++i) { for (int j = 10; j <= 19; ++j) { assert (new String( db.get(String.format("%dx%d", i, j).getBytes())).equals( String.format("%d", i * j))); System.out.format("%s ", new String(db.get( String.format("%dx%d", i, j).getBytes()))); } System.out.println(""); } value = db.get("1x1".getBytes()); assert (value != null); value = db.get("world".getBytes()); assert (value == null); value = db.get(readOptions, "world".getBytes()); assert (value == null); final byte[] testKey = "asdf".getBytes(); final byte[] testValue = "asdfghjkl;'?><MNBVCXZQWERTYUIOP{+_)(*&^%$#@".getBytes(); db.put(testKey, testValue); byte[] testResult = db.get(testKey); assert (testResult != null); assert (Arrays.equals(testValue, testResult)); assert (new String(testValue).equals(new String(testResult))); testResult = db.get(readOptions, testKey); assert (testResult != null); assert (Arrays.equals(testValue, testResult)); assert (new String(testValue).equals(new String(testResult))); final byte[] insufficientArray = new byte[10]; final byte[] enoughArray = new byte[50]; int len; len = db.get(testKey, insufficientArray); assert (len > insufficientArray.length); len = db.get("asdfjkl;".getBytes(), enoughArray); assert (len == RocksDB.NOT_FOUND); len = db.get(testKey, enoughArray); assert (len == testValue.length); len = db.get(readOptions, testKey, insufficientArray); assert (len > insufficientArray.length); len = db.get(readOptions, "asdfjkl;".getBytes(), enoughArray); assert (len == RocksDB.NOT_FOUND); len = db.get(readOptions, testKey, enoughArray); assert (len == testValue.length); db.remove(testKey); len = db.get(testKey, enoughArray); assert (len == RocksDB.NOT_FOUND); // repeat the test with WriteOptions try (final WriteOptions writeOpts = new WriteOptions()) { writeOpts.setSync(true); writeOpts.setDisableWAL(true); db.put(writeOpts, testKey, testValue); len = db.get(testKey, enoughArray); assert (len == testValue.length); assert (new String(testValue).equals( new String(enoughArray, 0, len))); } try { for (final TickerType statsType : TickerType.values()) { if (statsType != TickerType.TICKER_ENUM_MAX) { stats.getTickerCount(statsType); } } System.out.println("getTickerCount() passed."); } catch (final Exception e) { System.out.println("Failed in call to getTickerCount()"); assert (false); //Should never reach here. } try { for (final HistogramType histogramType : HistogramType.values()) { if (histogramType != HistogramType.HISTOGRAM_ENUM_MAX) { HistogramData data = stats.getHistogramData(histogramType); } } System.out.println("getHistogramData() passed."); } catch (final Exception e) { System.out.println("Failed in call to getHistogramData()"); assert (false); //Should never reach here. } try (final RocksIterator iterator = db.newIterator()) { boolean seekToFirstPassed = false; for (iterator.seekToFirst(); iterator.isValid(); iterator.next()) { iterator.status(); assert (iterator.key() != null); assert (iterator.value() != null); seekToFirstPassed = true; } if (seekToFirstPassed) { System.out.println("iterator seekToFirst tests passed."); } boolean seekToLastPassed = false; for (iterator.seekToLast(); iterator.isValid(); iterator.prev()) { iterator.status(); assert (iterator.key() != null); assert (iterator.value() != null); seekToLastPassed = true; } if (seekToLastPassed) { System.out.println("iterator seekToLastPassed tests passed."); } iterator.seekToFirst(); iterator.seek(iterator.key()); assert (iterator.key() != null); assert (iterator.value() != null); System.out.println("iterator seek test passed."); } System.out.println("iterator tests passed."); final List<byte[]> keys = new ArrayList<>(); try (final RocksIterator iterator = db.newIterator()) { for (iterator.seekToLast(); iterator.isValid(); iterator.prev()) { keys.add(iterator.key()); } } Map<byte[], byte[]> values = db.multiGet(keys); assert (values.size() == keys.size()); for (final byte[] value1 : values.values()) { assert (value1 != null); } values = db.multiGet(new ReadOptions(), keys); assert (values.size() == keys.size()); for (final byte[] value1 : values.values()) { assert (value1 != null); } } catch (final RocksDBException e) { System.err.println(e); } } }}The above is the entire content of RocksDB installation and application in Java introduced to you this time. 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