From: | Manfred Koizar <mkoi-pg(at)aon(dot)at> |
---|---|
To: | Alvaro Herrera <alvherre(at)dcc(dot)uchile(dot)cl> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Static snapshot data |
Date: | 2003-05-23 10:17:21 |
Message-ID: | v8srcv0dmiaslo6ieeuhqcfdupoqkjoehk@4ax.com |
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Lists: | pgsql-hackers pgsql-patches |
On Sat, 17 May 2003 19:14:25 -0400, Alvaro Herrera
<alvherre(at)dcc(dot)uchile(dot)cl> 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?
Servus
Manfred
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