Re: Static snapshot data

On Sat, 17 May 2003 19:14:25 -0400, Alvaro Herrera
 wrote:
>> >The user can
>> >change from READ COMMITTED to SERIALIZABLE when starting a
>> >subtransaction, but not the other way around.
>> 
>> You cannot propose this and agree to my three rules at the same time.
>> Rule 3 says that these two sequences of commands are equivalent:
>> [example]
>
>I see.  Then I don't fully agree with your rules.  Let's say I find that
>the rules are very good guidelines, but they fail WRT the isolation
>level, which is a special exception.

If there is not a compelling reason for making things more
complicated, I vote for implementing the most simple usable solution,
i.e. the whole transaction tree has to run with the same isolation
level.

If SERIALIZABLE subtransactions in a READ COMMITTED transaction are a
useful feature, this enhancement can be added later without breaking
compatibility.

BTW, do we have to invent a new syntax for starting and ending
subtransactions?  COMMIT/ROLLBACK should be no problem.  But does
BEGIN [subtransaction] conflict with BEGIN ... END in pl/pgslq?

ServusManfred