Logic performing several hundred queries takes significantly more time after migration from Hibernate 3

Issue

• Migrating from Hibernate 3 to Hibernate 4/5
• Execution of several hundred queries within a transaction is significantly slower in Hibernate 4/5

• High incidence in thread dumps of stack frames like the following

      ...
      at org.hibernate.event.internal.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:165)
      at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:156)
      at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:89)
      at org.hibernate.event.internal.DefaultAutoFlushEventListener.onAutoFlush(DefaultAutoFlushEventListener.java:61)
      at org.hibernate.internal.SessionImpl.autoFlushIfRequired(SessionImpl.java:1166)
      at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1223)
      at org.hibernate.internal.QueryImpl.list(QueryImpl.java:101)
      ...