Is Hibernate used using pessimistic or optimistic locking?

Question

All my classes have

@version

so I suggested that they used optimistic locking.

But I reserve the following exception in my journals, which seem to indicate the use of pessimistic blocking. So what is it? (I want to use optimistic locking)

update Song set acoustidFingerprint=?, acoustidId=?, album=?, albumArtist=?, albumArtistSort=?, albumSort=?, amazonId=?, arranger=?, artist=?, artistSort=?, artists=?, barcode=?, bpm=?, catalogNo=?, comment=?, composer=?, composerSort=?, conductor=?, country=?, custom1=?, custom2=?, custom3=?, custom4=?, custom5=?, discNo=?, discSubtitle=?, discTotal=?, djmixer=?, duration=?, encoder=?, engineer=?, fbpm=?, filename=?, genre=?, grouping=?, isCompilation=?, isrc=?, keyOfSong=?, language=?, lastModified=?, lyricist=?, lyrics=?, media=?, mixer=?, mood=?, musicbrainzArtistId=?, musicbrainzDiscId=?, musicbrainzOriginalReleaseId=?, musicbrainzRecordingId=?, musicbrainzReleaseArtistId=?, musicbrainzReleaseCountry=?, musicbrainzReleaseGroupId=?, musicbrainzReleaseId=?, musicbrainzReleaseStatus=?, musicbrainzReleaseType=?, musicbrainzWorkId=?, musicipId=?, occasion=?, originalAlbum=?, originalArtist=?, originalLyricist=?, originalYear=?, producer=?, quality=?, rating=?, recordLabel=?, releaseYear=?, remixer=?, script=?, subtitle=?, tags=?, tempo=?, title=?, titleSort=?, track=?, trackTotal=?, urlDiscogsArtistSite=?, urlDiscogsReleaseSite=?, urlLyricsSite=?, urlOfficialArtistSite=?, urlOfficialReleaseSite=?, urlWikipediaArtistSite=?, urlWikipediaReleaseSite=?, version=? where recNo=? and version=? [50200-172] **org.hibernate.PessimisticLockException: Timeout trying to lock table ; SQL statement:** update Song set acoustidFingerprint=?, acoustidId=?, album=?, albumArtist=?, albumArtistSort=?, albumSort=?, amazonId=?, arranger=?, artist=?, artistSort=?, artists=?, barcode=?, bpm=?, catalogNo=?, comment=?, composer=?, composerSort=?, conductor=?, country=?, custom1=?, custom2=?, custom3=?, custom4=?, custom5=?, discNo=?, discSubtitle=?, discTotal=?, djmixer=?, duration=?, encoder=?, engineer=?, fbpm=?, filename=?, genre=?, grouping=?, isCompilation=?, isrc=?, keyOfSong=?, language=?, lastModified=?, lyricist=?, lyrics=?, media=?, mixer=?, mood=?, musicbrainzArtistId=?, musicbrainzDiscId=?, musicbrainzOriginalReleaseId=?, musicbrainzRecordingId=?, musicbrainzReleaseArtistId=?, musicbrainzReleaseCountry=?, musicbrainzReleaseGroupId=?, musicbrainzReleaseId=?, musicbrainzReleaseStatus=?, musicbrainzReleaseType=?, musicbrainzWorkId=?, musicipId=?, occasion=?, originalAlbum=?, originalArtist=?, originalLyricist=?, originalYear=?, producer=?, quality=?, rating=?, recordLabel=?, releaseYear=?, remixer=?, script=?, subtitle=?, tags=?, tempo=?, title=?, titleSort=?, track=?, trackTotal=?, urlDiscogsArtistSite=?, urlDiscogsReleaseSite=?, urlLyricsSite=?, urlOfficialArtistSite=?, urlOfficialReleaseSite=?, urlWikipediaArtistSite=?, urlWikipediaReleaseSite=?, version=? where recNo=? and version=? [50200-172] at org.hibernate.dialect.H2Dialect$2.convert(H2Dialect.java:317) at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125) at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110) at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:129) at org.hibernate.engine.jdbc.internal.proxy.AbstractProxyHandler.invoke(AbstractProxyHandler.java:81) at com.sun.proxy.$Proxy22.executeUpdate(Unknown Source) at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3123) at org.hibernate.persister.entity.AbstractEntityPersister.updateOrInsert(AbstractEntityPersister.java:3021) at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3350) at org.hibernate.action.internal.EntityUpdateAction.execute(EntityUpdateAction.java:140) at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:362) at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:354) at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:276) at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:326) at org.hibernate.event.internal.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:62) at org.hibernate.internal.SessionImpl.autoFlushIfRequired(SessionImpl.java:1182) at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1611) at org.hibernate.internal.CriteriaImpl.list(CriteriaImpl.java:374) at com.jthink.songkong.db.SongCache.loadSongsFromDatabase(SongCache.java:58) at com.jthink.songkong.analyse.analyser.SongGroup.getSongs(SongGroup.java:48) at com.jthink.songkong.analyse.analyser.MergeMusicBrainzMatches.matchToMissingTracks(MergeMusicBrainzMatches.java:318) at com.jthink.songkong.analyse.analyser.MergeMusicBrainzMatches.call(MergeMusicBrainzMatches.java:105) at com.jthink.songkong.analyse.analyser.MergeMusicBrainzMatches.call(MergeMusicBrainzMatches.java:40) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334) at java.util.concurrent.FutureTask.run(FutureTask.java:166) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:722) Caused by: org.h2.jdbc.JdbcSQLException: Timeout trying to lock table ; SQL statement: update Song set acoustidFingerprint=?, acoustidId=?, album=?, albumArtist=?, albumArtistSort=?, albumSort=?, amazonId=?, arranger=?, artist=?, artistSort=?, artists=?, barcode=?, bpm=?, catalogNo=?, comment=?, composer=?, composerSort=?, conductor=?, country=?, custom1=?, custom2=?, custom3=?, custom4=?, custom5=?, discNo=?, discSubtitle=?, discTotal=?, djmixer=?, duration=?, encoder=?, engineer=?, fbpm=?, filename=?, genre=?, grouping=?, isCompilation=?, isrc=?, keyOfSong=?, language=?, lastModified=?, lyricist=?, lyrics=?, media=?, mixer=?, mood=?, musicbrainzArtistId=?, musicbrainzDiscId=?, musicbrainzOriginalReleaseId=?, musicbrainzRecordingId=?, musicbrainzReleaseArtistId=?, musicbrainzReleaseCountry=?, musicbrainzReleaseGroupId=?, musicbrainzReleaseId=?, musicbrainzReleaseStatus=?, musicbrainzReleaseType=?, musicbrainzWorkId=?, musicipId=?, occasion=?, originalAlbum=?, originalArtist=?, originalLyricist=?, originalYear=?, producer=?, quality=?, rating=?, recordLabel=?, releaseYear=?, remixer=?, script=?, subtitle=?, tags=?, tempo=?, title=?, titleSort=?, track=?, trackTotal=?, urlDiscogsArtistSite=?, urlDiscogsReleaseSite=?, urlLyricsSite=?, urlOfficialArtistSite=?, urlOfficialReleaseSite=?, urlWikipediaArtistSite=?, urlWikipediaReleaseSite=?, version=? where recNo=? and version=? [50200-172] at org.h2.message.DbException.getJdbcSQLException(DbException.java:329) at org.h2.message.DbException.get(DbException.java:158) at org.h2.command.Command.filterConcurrentUpdate(Command.java:281) at org.h2.command.Command.executeUpdate(Command.java:237) at org.h2.jdbc.JdbcPreparedStatement.executeUpdateInternal(JdbcPreparedStatement.java:154) at org.h2.jdbc.JdbcPreparedStatement.executeUpdate(JdbcPreparedStatement.java:140) at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeUpdate(NewProxyPreparedStatement.java:105) at sun.reflect.GeneratedMethodAccessor55.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:601) at org.hibernate.engine.jdbc.internal.proxy.AbstractStatementProxyHandler.continueInvocation(AbstractStatementProxyHandler.java:122) ... 24 more 

Answer 1

You are using optimistic locking , as your UPDATE already indicates:

 where recNo=? and version=? 

Having a version column is what an optimistic lock is.

You have been misled by PessimisticLockException , which may be caused by explicit or implicit row-level locking .

You must understand that locks are acquired implicitly in strings to avoid dirty writing. This book explains this topic with many diagrams and code examples.

Answer 2

This exception is related to Lock TimeOut.

Caused by: org.h2.jdbc.JdbcSQLException: timeout trying to lock the table;

Check the solution here

Hibernate also provides mechanisms for implementing both types of locks in your applications.

Your blocking strategy may be optimistic or pessimistic.

Optimistic

Optimistic locks that can be executed by several transactions without affecting each other, and therefore transactions can continue without blocking the data resources that they affect. Before committing a transaction, each transaction verifies that no other transaction has changed its data. If the check shows inconsistent modifications, the transactional transaction goes back [1].

Pessimistic

Pessimistic locking assumes that parallel transactions will conflict with each other and require that resources be locked after they are read and only unlocked after the application has finished using data.

Details can be found here.

Answer 3

Most likely, you will use a different database for testing than in the LIVE environment.

H2 may cause errors that may not appear in the LIVE Database, such as Oracle, MySQL aso. So even your code is correct, but H2 can be messy.

MVCC = true works fine. At the same time, you should make sure that you have complete integration tests for LIVE-like systems for your use case, in order to check the behavior of the LIVE Database.