java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
at java.util.HashMap$EntryIterator.next(Unknown Source)
at java.util.HashMap$EntryIterator.next(Unknown Source)
at org.hibernate.mapping.Table.cleanseUniqueKeyMap(Table.java:291)
at org.hibernate.mapping.Table.cleanseUniqueKeyMapIfNeeded(Table.java:262)
at org.hibernate.mapping.Table.getUniqueKeys(Table.java:251)
at org.hibernate.mapping.Table.getUniqueKeyIterator(Table.java:247)
at org.hibernate.mapping.Table.sqlCreateString(Table.java:530)
at org.hibernate.cfg.Configuration.generateSchemaCreationScript(Configuration.java:1028)
at org.hibernate.tool.hbm2ddl.SchemaExport.<init>(SchemaExport.java:125)
at org.hibernate.tool.hbm2x.Hbm2DDLExporter.doStart(Hbm2DDLExporter.java:165)
at org.hibernate.tool.hbm2x.AbstractExporter.start(AbstractExporter.java:96)
at org.hibernate.tool.ant.ExporterTask.execute(ExporterTask.java:40)
at org.hibernate.tool.ant.HibernateToolTask.execute(HibernateToolTask.java:186)

Problematic code was introduced with
HHH-6707 - One-to-One mapping with foreign key in target table and foreign key b…