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rocksDB is aembeddablepersistent key-value storage.
The following introduction is from the Chinese official website of rocksDB
https://rocksdb.org.cn/
It has the following four characteristics
1 High performance: RocksDB uses a log-structured database engine written in C, for better performance, this engine is written in C++written. Key and value are arbitrary size byte streams.
2 Optimized for fast storage: RocksDB is specially optimized for fast and low-latency storage devices (such as flash or high-speed hard drives). RocksDB will maximize the high-speed read and write performance of flash and RAM.
3 Adaptability: RocksDB is suitable for a variety of different workloads. From data storage engines like MyRocks, to application data caching, even some embedded workloads, RocksDB can easily handle these different data workload requirements.
4 Basic and advanced database operations RocksDB provides some basic operations, such as opening and closing the database. For advanced operations such as merging and compression filtering, it also provides read and write support.
;RockDB installation and usage
There are many ways to install rocksDB. Since the official does not provide binary libraries for the corresponding platform, you need to compile and use them yourself.
The installation of rocksDB is simple, but it requires a change in perspective on rocksDB. It is not a heavy-duty database, but an embedded key-value storage. This means that as long as you add the rocksDB dependency to your Maven project, you can try it in the development environment. If you don't understand this, you may fall into the following two not recommended installation methods.
Method One Go to the rocksDB official website and find out 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????? How is it different from the mysql or mongo I used before? Why is there no start.sh or start.bat script? Do I have to write one? After writing and compiling, I still don't know how to associate it with the rocksDB library. What should I do, I'm C++All forgotten.
Method Two Use pyrocksDB (not recommended)
http://pyrocksdb.readthedocs.io/en/latest/installation.html
For detailed installation documents, see the installation documents on the pyrocksDB official website.
The above two methods are for those familiar with C++ It is friendly for developers of Python or Java, but not very friendly for Java developers.
Next, I will introduce the third method.
Method 3: Use Maven (recommended)
Create a new Maven project and modify the pom.xml to add dependencies
<dependency> <groupId>org.rocksdb</groupId> <artifactId>rocksdbjni</artifactId> <version>5.8.6</version> </dependency>
You can choose your favorite version.
Then set a higher language level for Maven, which I have set globally to1.8
<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>
By now, the environment is set up, and you might have returned to the familiar Java world.
Then copy a class from the source code package, modify the run configuration in the IDE, add a database storage path during program execution, and you can run the test. I will give this class at the end of the article.
The console output will have logs, and some new files will also appear in the file.
There will be more updates about the rockDB development API and its application in production, and everyone is encouraged to pay attention.
// 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(10000000,10000, 10)) {
try (final RocksDB db = RocksDB.open(options, db_path_not_found)) {
assert (false);
}
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(""));
}
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(readOptions, "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);
}
}
System.err.println(e);
}
}
}
}
That is all the content of the installation and application of RocksDB in Java that we have introduced to you this time. If you have any questions after learning, you can discuss them in the comment area below. Thank you for your support of the Yelling Tutorial.