Possible race condition when removing same elemens from the same document (attachment, object, class property) in different threads

Error number 3233 in 3: Exception while deleting attachment Main.TestPage-with-history.xar of document XWiki.XWikiPreferences
Wrapped Exception: Failed to commit or rollback transaction. Root cause []
com.xpn.xwiki.XWikiException: Error number 3233 in 3: Exception while deleting attachment Main.TestPage-with-history.xar of document XWiki.XWikiPreferences
Wrapped Exception: Failed to commit or rollback transaction. Root cause []
	at com.xpn.xwiki.store.XWikiHibernateAttachmentStore.deleteXWikiAttachment(XWikiHibernateAttachmentStore.java:293)
	at com.xpn.xwiki.store.XWikiHibernateAttachmentStore.deleteXWikiAttachment(XWikiHibernateAttachmentStore.java:215)
	at com.xpn.xwiki.doc.XWikiDocument.deleteAttachment(XWikiDocument.java:4500)
	at com.xpn.xwiki.doc.XWikiDocument.deleteAttachment(XWikiDocument.java:4480)
	at com.xpn.xwiki.web.DeleteAttachmentAction.action(DeleteAttachmentAction.java:127)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:213)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:115)
	at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
	at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
	at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
	at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1221)
	at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:129)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.xwiki.wysiwyg.server.filter.ConversionFilter.doFilter(ConversionFilter.java:152)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at com.xpn.xwiki.plugin.webdav.XWikiDavFilter.doFilter(XWikiDavFilter.java:68)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:218)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:112)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399)
	at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
	at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
	at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
	at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
	at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
	at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
	at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)


Wrapped Exception:

org.hibernate.exception.GenericJDBCException: Could not execute JDBC batch update
	at org.hibernate.exception.SQLStateConverter.handledNonSpecificException(SQLStateConverter.java:140)
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:128)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
	at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:275)
	at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:268)
	at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:184)
	at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
	at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
	at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216)
	at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383)
	at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133)
	at com.xpn.xwiki.store.XWikiHibernateBaseStore.endTransaction(XWikiHibernateBaseStore.java:871)
	at com.xpn.xwiki.store.XWikiHibernateBaseStore.endTransaction(XWikiHibernateBaseStore.java:842)
	at com.xpn.xwiki.store.XWikiHibernateAttachmentStore.deleteXWikiAttachment(XWikiHibernateAttachmentStore.java:289)
	at com.xpn.xwiki.store.XWikiHibernateAttachmentStore.deleteXWikiAttachment(XWikiHibernateAttachmentStore.java:215)
	at com.xpn.xwiki.doc.XWikiDocument.deleteAttachment(XWikiDocument.java:4500)
	at com.xpn.xwiki.doc.XWikiDocument.deleteAttachment(XWikiDocument.java:4480)
	at com.xpn.xwiki.web.DeleteAttachmentAction.action(DeleteAttachmentAction.java:127)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:213)
	at com.xpn.xwiki.web.XWikiAction.execute(XWikiAction.java:115)
	at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
	at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
	at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
	at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
	at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1221)
	at com.xpn.xwiki.web.ActionFilter.doFilter(ActionFilter.java:129)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.xwiki.wysiwyg.server.filter.ConversionFilter.doFilter(ConversionFilter.java:152)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at com.xpn.xwiki.plugin.webdav.XWikiDavFilter.doFilter(XWikiDavFilter.java:68)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.xwiki.container.servlet.filters.internal.SavedRequestRestorerFilter.doFilter(SavedRequestRestorerFilter.java:218)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.xwiki.container.servlet.filters.internal.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:112)
	at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1212)
	at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:399)
	at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
	at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
	at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
	at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
	at org.mortbay.jetty.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:230)
	at org.mortbay.jetty.handler.HandlerCollection.handle(HandlerCollection.java:114)
	at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
	at org.mortbay.jetty.Server.handle(Server.java:326)
	at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
	at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
	at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
	at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
	at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
	at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
	at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
Caused by: java.sql.BatchUpdateException: failed batch
	at org.hsqldb.jdbc.jdbcStatement.executeBatch(Unknown Source)
	at org.hsqldb.jdbc.jdbcPreparedStatement.executeBatch(Unknown Source)
	at org.apache.commons.dbcp.DelegatingStatement.executeBatch(DelegatingStatement.java:297)
	at org.apache.commons.dbcp.DelegatingStatement.executeBatch(DelegatingStatement.java:297)
	at org.apache.commons.dbcp.DelegatingStatement.executeBatch(DelegatingStatement.java:297)
	at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:70)
	at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:268)
	... 50 more