In short: prior to version 9.2, postgres's "serializable" level still allowed some transaction patterns that would be rejected by a strictly serial execution. L

In short: prior to version 9.2, postgres's "serializable" level still allowed some transaction patterns that would be rejected by a strictly serial execution. Later versions prevent it. This paper: http://dl.acm.org/citation.cfm?id=1376690 http://dl.acm.org/citation.cfm?id=1376690 outlines the general issue. This paper discusses Postgres's solution: http://drkp.net/papers/ssi-vldb12.pdf http://drkp.net/papers/ssi-vldb12.pdf