Hibernate
/
hibernate-orm
mirror of https://github.com/hibernate/hibernate-orm
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

HHH-18947 UUID v7 - Use randomized counter instead of counter + random 

This will add approximately ten bits of entropy to generated UUID,
          while preserving uniqueness and monotonicity
This commit is contained in:
Čedomir Igaly 2024-12-14 14:00:16 +01:00 committed by Christian Beikov
parent 57c0b26d86
commit 2215d2b9bf
1 changed files with 24 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

53
hibernate-core/src/main/java/org/hibernate/id/uuid/UuidVersion7Strategy.java
View File

@ -13,7 +13,6 @@ import org.hibernate.Internal;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import org.hibernate.id.UUIDGenerationStrategy;
import static java.time.temporal.ChronoUnit.MILLIS;
/**
* Implements UUID Version 7 generation strategy as defined by the <a href="https://datatracker.ietf.org/doc/html/rfc9562#name-uuid-version-7">RFC 9562</a>.
@ -26,8 +25,7 @@ import static java.time.temporal.ChronoUnit.MILLIS;
* to guarantee additional monotonicity.
* </li>
* <li>2 bits - variant field, set to 0b10.</li>
* <li>14 bits - counter to guarantee additional monotonicity, resets to 0 when timestamp changes. </li>
* <li>48 bits - pseudorandom data to provide uniqueness.</li>
* <li>62 bits - pseudorandom counter to guarantee additional monotonicity, uniqueness, and good entropy.</li>
* </ul>
*
* @author Cedomir Igaly
@ -37,6 +35,8 @@ import static java.time.temporal.ChronoUnit.MILLIS;
*/
public class UuidVersion7Strategy implements UUIDGenerationStrategy, UuidValueGenerator {
private static final long MAX_RANDOM_SEQUENCE = 0x3FFF_FFFF_FFFF_FFFFL;
public static final UuidVersion7Strategy INSTANCE = new UuidVersion7Strategy();
private static class Holder {
@ -44,36 +44,37 @@ public class UuidVersion7Strategy implements UUIDGenerationStrategy, UuidValueGe
}
public record State(Instant lastTimestamp, int lastSequence) {
public record State(Instant lastTimestamp, long lastSequence, long nanos) {
State(Instant lastTimestamp, long lastSequence) {
this( lastTimestamp, lastSequence, nanos( lastTimestamp ) );
}
public long millis() {
return lastTimestamp.toEpochMilli();
}
public long nanos() {
return (long) ( ( lastTimestamp.getNano() % 1_000_000L ) * 0.004096 );
private static long nanos(Instant timestamp) {
return (long) ((timestamp.getNano() % 1_000_000L) * 0.004096);
}
public State getNextState() {
final Instant now = Instant.now();
if ( lastTimestamp.toEpochMilli() < now.toEpochMilli() ) {
return new State(
now.truncatedTo( MILLIS ),
randomSequence()
);
if ( lastTimestamp.toEpochMilli() < now.toEpochMilli() ||
lastTimestamp.toEpochMilli() == now.toEpochMilli() && nanos < nanos( now ) ) {
return new State( now, randomSequence() );
}
else if ( lastSequence == 0x3FFF ) {
return new State(
lastTimestamp.plusMillis( 1 ),
Holder.numberGenerator.nextInt( 1 << 14 )
);
final long nextSequence = lastSequence + Holder.numberGenerator.nextLong( 0xFFFF_FFFFL );
if ( nextSequence > MAX_RANDOM_SEQUENCE ) {
return new State( lastTimestamp.plusNanos( 250 ), randomSequence() );
}
else {
return new State( lastTimestamp, lastSequence + 1 );
return new State( lastTimestamp, nextSequence );
}
}
private static int randomSequence() {
return Holder.numberGenerator.nextInt( 1 << 14 );
private static long randomSequence() {
return Holder.numberGenerator.nextLong( MAX_RANDOM_SEQUENCE );
}
}
@ -81,11 +82,11 @@ public class UuidVersion7Strategy implements UUIDGenerationStrategy, UuidValueGe
@Internal
public UuidVersion7Strategy() {
this( Instant.EPOCH, Integer.MIN_VALUE );
this( Instant.EPOCH, Holder.numberGenerator.nextLong( MAX_RANDOM_SEQUENCE ) );
}
@Internal
public UuidVersion7Strategy(final Instant initialTimestamp, final int initialSequence) {
public UuidVersion7Strategy(final Instant initialTimestamp, final long initialSequence) {
this.lastState = new AtomicReference<>( new State( initialTimestamp, initialSequence ) );
}
@ -115,14 +116,8 @@ public class UuidVersion7Strategy implements UUIDGenerationStrategy, UuidValueGe
| state.nanos() & 0xFFFL,
// LSB bits 0-1 - variant = 4
0x8000_0000_0000_0000L
// LSB bits 2-15 - counter
| (long) state.lastSequence << 48
// LSB bits 16-63 - pseudorandom data
| randomNode()
// LSB bits 2-15 - pseudorandom counter
| state.lastSequence
);
}
private static long randomNode() {
return Holder.numberGenerator.nextLong( 0x1_0000_0000_0000L ) | 0x1000_0000_0000L;
}
}