Re: serializable read only deferrable

Tom Lane  wrote:
> "Kevin Grittner"  writes:
>> I'm reviving the discussion on the subject topic because I just
>> had an epiphany which makes it seem simple to implement. The
>> concept of this is that if you start a SERIALIZABLE READ ONLY
>> transaction in an SSI environment when certain conditions are
>> true, it doesn't need to acquire predicate locks or test for
>> rw-conflicts.
> 
> I assume this would have to be a "hard" definition of READ ONLY,
> not the rather squishy definition we use now? How would we manage
> the compatibility implications?
If there are issues with whether READ ONLY covers the right ground,
it's likely to affect more than this particular issue -- I've taken
advantage of the READ ONLY property of transactions to allow quite a
few novel optimizations to SSI beyond what is presented in Cahill's
doctoral work.
I'm excluding temporary tables from SSI on the grounds that they are
only read and written by a single transaction and therefore can't be
a source of rw-dependencies, and I'm excluding system tables on the
grounds that they don't follow normal snapshot isolation rules.  Hint
bit rewrites are not an issue for SSI.  Are there any other squishy
aspect I might need to consider?
-Kevin