I happened across this page: http://en.wikipedia.org/wiki/Isolation_(database_systems) I was all set to be righteously indignant over the slander of PostgreSQL, but figured I should check the SQL standard to be sure of my ground. The only version of the standard I have available right now is the 2003 version, where I found: "The execution of concurrent SQL-transactions at isolation level SERIALIZABLE is guaranteed to be serializable. A serializable execution is defined to be an execution of the operations of concurrently executing SQL-transactions that produces the same effect as some serial execution of those same SQL-transactions. A serial execution is one in which each SQL-transaction executes to completion before the next SQL-transaction begins." and following the diagram of phenomena allowed at each level: "NOTE 53 * The exclusion of these phenomena for SQL-transactions executing at isolation level SERIALIZABLE is a consequence of the requirement that such transactions be serializable." The wikipedia page cites the ANSI/ISO SQL 99 standard, so the PostgreSQL documentation on the topic is apparently based on an earlier version. Is an update in order? Note that I would not want to pay the performance penalty for full compliance with the later standards. The cases where there is a difference seem unlikely to ever come up in the environments where I work, so any effort in changing PostgreSQL behavior toward closer conformance would be totally wasted from my perspective. -Kevin
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