When a change affects multiple builds, Pulse will detect and reuse an existing changelist. There is currently a race in this detection, which can lead to duplicate changelists. If a third build detects the same change, it will then get an exception:

SEVERE: query did not return a unique result: 2
org.springframework.dao.IncorrectResultSizeDataAccessException: query
did not return a unique result: 2
       at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:658)
       at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:408)
       at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:367)
       at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:328)
       at com.zutubi.pulse.model.persistence.hibernate.HibernateChangelistDao.findByRevision(HibernateChangelistDao.java:116)
       at sun.reflect.GeneratedMethodAccessor830.invoke(Unknown Source)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
       at java.lang.reflect.Method.invoke(Unknown Source)
       at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
       at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:203)
       at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:162)
       at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:107)
       at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
       at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:209)
       at $Proxy7.findByRevision(Unknown Source)
       at com.zutubi.pulse.model.DefaultBuildManager.getChangelistByRevision(DefaultBuildManager.java:332)
       at sun.reflect.GeneratedMethodAccessor829.invoke(Unknown Source)
       at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
       at java.lang.reflect.Method.invoke(Unknown Source)