Good Resources on Debugging PostgreSql deadlocks

http://www.moioli.net/progetti/postgres-deadlocks-debugging-guidelines/

http://rhaas.blogspot.dk/2011/10/deadlocks.html

http://braindump.dk/tech/2007/04/18/debugging-postgresql-locks/

http://stackoverflow.com/questions/29532072/postmortem-deadlock-debugging-in-postgresql

http://stackoverflow.com/questions/18297478/deadlock-in-postgres-on-simple-update-query

http://blog.2ndquadrant.com/postgresql-anti-patterns-read-modify-write-cycles/

http://vladmihalcea.com/2014/09/14/a-beginners-guide-to-database-locking-and-the-lost-update-phenomena/

http://stackoverflow.com/questions/34436253/transaction-in-postgresql

https://en.wikibooks.org/wiki/Java_Persistence/Locking#Advanced

http://vladmihalcea.com/2013/11/15/optimistic-locking-retry-with-jpa/