246 lines
6.5 KiB
Markdown
246 lines
6.5 KiB
Markdown
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# ULID Creator
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A Java library for generating [ULIDs](https://github.com/ulid/spec) (Universally Unique Lexicographically Sortable Identifier).
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* Generated in lexicographical order;
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* Can be stored as a UUID/GUID;
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* Can be stored as a string of 26 chars;
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* Can be stored as an array of 16 bytes;
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* String format is encoded to [Crockford's base32](https://www.crockford.com/base32.html);
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* String format is URL safe and case insensitive.
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How to Use
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------------------------------------------------------
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Create a ULID:
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```java
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Ulid ulid = UlidCreator.getUlid();
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```
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Create a Monotonic ULID:
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```java
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Ulid ulid = UlidCreator.getMonotonicUlid();
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```
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### Maven dependency
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Add these lines to your `pom.xml`.
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```xml
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<!-- https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator -->
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<dependency>
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<groupId>com.github.f4b6a3</groupId>
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<artifactId>ulid-creator</artifactId>
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<version>3.2.0</version>
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</dependency>
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```
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See more options in [maven.org](https://search.maven.org/artifact/com.github.f4b6a3/ulid-creator).
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Module name: `com.github.f4b6a3.ulid`.
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### ULID
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The ULID is a 128 bit long identifier. The first 48 bits represent the count of milliseconds since Unix Epoch, 1970-01-01. The remaining 80 bits are generated by a secure random number generator.
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```java
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// Generate a ULID
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Ulid ulid = UlidCreator.getUlid();
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```
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```java
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// Generate a ULID with a specific time
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Ulid ulid = UlidCreator.getUlid(1234567890);
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```
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Sequence of ULIDs:
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```text
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01EX8Y21KBH49ZZCA7KSKH6X1C
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01EX8Y21KBJTFK0JV5J20QPQNR
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01EX8Y21KBG2CS1V6WQCTVM7K6
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01EX8Y21KB8HPZNBP3PTW7HVEY
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01EX8Y21KB3HZV38VAPTPAG1TY
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01EX8Y21KB9FTEJHPAGAKYG9Z8
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01EX8Y21KBQGKGH2SVPQAYEFFC
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01EX8Y21KBY17J9WR9KQR8SE7H
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01EX8Y21KCVHYSJGVK4HBXDMR9 < millisecond changed
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01EX8Y21KC668W3PEDEAGDHMVG
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01EX8Y21KC53D2S5ADQ2EST327
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01EX8Y21KCPQ3TENMTY1S7HV56
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01EX8Y21KC3755QF9STQEV05EB
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01EX8Y21KC5ZSHK908GMDK69WE
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01EX8Y21KCSGJS8S1FVS06B3SX
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01EX8Y21KC6ZBWQ0JBV337R1CN
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^ look
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|---------|--------------|
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time random
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```
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### Monotonic ULID
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The Monotonic ULID is a 128 bit long identifier. The first 48 bits represent the count of milliseconds since Unix Epoch, 1970-01-01. The remaining 80 bits are generated by a secure random number generator.
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The random component is incremented by 1 whenever the current millisecond is equal to the previous one. But when the current millisecond is different, the random component changes to another random value.
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```java
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// Generate a Monotonic ULID
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Ulid ulid = UlidCreator.getMonotonicUlid();
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```
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```java
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// Generate a Monotonic ULID with a specific time
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Ulid ulid = UlidCreator.getMonotonicUlid(1234567890);
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```
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Sequence of Monotonic ULIDs:
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```text
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01EX8Y7M8MDVX3M3EQG69EEMJW
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01EX8Y7M8MDVX3M3EQG69EEMJX
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01EX8Y7M8MDVX3M3EQG69EEMJY
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01EX8Y7M8MDVX3M3EQG69EEMJZ
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01EX8Y7M8MDVX3M3EQG69EEMK0
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01EX8Y7M8MDVX3M3EQG69EEMK1
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01EX8Y7M8MDVX3M3EQG69EEMK2
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01EX8Y7M8MDVX3M3EQG69EEMK3
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01EX8Y7M8N1G30CYF2PJR23J2J < millisecond changed
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01EX8Y7M8N1G30CYF2PJR23J2K
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01EX8Y7M8N1G30CYF2PJR23J2M
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01EX8Y7M8N1G30CYF2PJR23J2N
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01EX8Y7M8N1G30CYF2PJR23J2P
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01EX8Y7M8N1G30CYF2PJR23J2Q
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01EX8Y7M8N1G30CYF2PJR23J2R
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01EX8Y7M8N1G30CYF2PJR23J2S
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^ look ^ look
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|---------|--------------|
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time random
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```
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### Other usage examples
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Create a ULID from a canonical string (26 chars):
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```java
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Ulid ulid = Ulid.from("0123456789ABCDEFGHJKMNPQRS");
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```
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Convert a ULID into a canonical string in upper case:
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```java
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String string = ulid.toUpperCase(); // 0123456789ABCDEFGHJKMNPQRS
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```
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Convert a ULID into a canonical string in lower case:
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```java
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String string = ulid.toLowerCase(); // 0123456789abcdefghjkmnpqrs
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```
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Convert a ULID into a UUID:
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```java
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UUID uuid = ulid.toUuid(); // 0110c853-1d09-52d8-d73e-1194e95b5f19
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```
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Convert a ULID into a [RFC-4122](https://tools.ietf.org/html/rfc4122) UUID v4:
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```java
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UUID uuid = ulid.toRfc4122().toUuid(); // 0110c853-1d09-42d8-973e-1194e95b5f19
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// ^ UUID v4
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```
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Convert a ULID into a byte array:
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```java
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byte[] bytes = ulid.toBytes(); // 16 bytes (128 bits)
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```
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Get the creation instant of a ULID:
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```java
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Instant instant = ulid.getInstant(); // 2007-02-16T02:13:14.633Z
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```
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```java
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// static method
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Instant instant = Ulid.getInstant("0123456789ABCDEFGHJKMNPQRS"); // 2007-02-16T02:13:14.633Z
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```
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Get the time component of a ULID:
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```java
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long time = ulid.getTime(); // 1171591994633
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```
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```java
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// static method
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long time = Ulid.getTime("0123456789ABCDEFGHJKMNPQRS"); // 1171591994633
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```
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Get the random component of a ULID:
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```java
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byte[] random = ulid.getRandom(); // 10 bytes (80 bits)
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```
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```java
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// static method
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byte[] random = Ulid.getRandom("0123456789ABCDEFGHJKMNPQRS"); // 10 bytes (80 bits)
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```
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Use a `UlidFactory` with `java.util.Random`:
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```java
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// use a `Random` instance
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UlidFactory factory = new DefaultFactory(new Random());
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Ulid ulid = factory.create();
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```
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Use a `UlidFactory` with a random generator of your choice:
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```java
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// use a method of any RNG with this signature: `void nextBytes(byte[])`
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import com.github.niceguy.random.AwesomeRandom; // a hypothetical RNG
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UlidFactory factory = new DefaultFactory(new AwesomeRandom()::nextBytes);
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Ulid ulid = factory.create();
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```
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(*) as long as it provides a void method like `nextBytes(byte[])`.
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Benchmark
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------------------------------------------------------
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This section shows benchmarks comparing `UlidCreator` to `java.util.UUID`.
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```
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--------------------------------------------------------------------------------
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THROUGHPUT (operations/msec) Mode Cnt Score Error Units
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--------------------------------------------------------------------------------
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UUID_randomUUID thrpt 5 2051,918 ± 24,797 ops/ms
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UUID_randomUUID_toString thrpt 5 1176,382 ± 32,709 ops/ms
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UlidCreator_getUlid thrpt 5 2738,998 ± 51,092 ops/ms
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UlidCreator_getUlid_toString thrpt 5 2548,178 ± 25,484 ops/ms
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UlidCreator_getMonotonicUlid thrpt 5 19807,920 ± 410,996 ops/ms
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UlidCreator_getMonotonicUlid_toString thrpt 5 13178,389 ± 147,323 ops/ms
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--------------------------------------------------------------------------------
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Total time: 00:08:01
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--------------------------------------------------------------------------------
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```
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System: JVM 8, Ubuntu 20.04, CPU i5-3330, 8G RAM.
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To execute the benchmark, run `./benchmark/run.sh`.
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Other identifier generators
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-------------------------------------------
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* [UUID Creator](https://github.com/f4b6a3/uuid-creator)
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* [TSID Creator](https://github.com/f4b6a3/tsid-creator)
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* [KSUID Creator](https://github.com/f4b6a3/ksuid-creator)
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