Обсуждение: new postgresql.conf

Just saw these:

#default_transaction_isolation = 'read committed'
#default_transaction_read_only = false

Does the second option control the new read only transaction mode?  I
thought 'read only' was just a new level of transaction isolation (ie. one
of the 4 sql standard ones), so why does it need its own GUC var?

Chris

On Mon, 28 Jul 2003, Christopher Kings-Lynne wrote:

> Just saw these:
> 
> #default_transaction_isolation = 'read committed'
> #default_transaction_read_only = false
> 
> Does the second option control the new read only transaction mode?  I
> thought 'read only' was just a new level of transaction isolation (ie. one
> of the 4 sql standard ones), so why does it need its own GUC var?

It is a transaction access mode, not an isolation level. ansi sql supports
two modes: read only and read write.

Gavin

"Christopher Kings-Lynne" <chriskl@familyhealth.com.au> writes:
> Just saw these:
> #default_transaction_isolation = 'read committed'
> #default_transaction_read_only = false
> Does the second option control the new read only transaction mode?

Yes.

> I thought 'read only' was just a new level of transaction isolation (ie. one
> of the 4 sql standard ones), so why does it need its own GUC var?

No, it's orthogonal to isolation.  A read-only transaction could
sensibly want either READ COMMITTED or SERIALIZABLE behavior, depending
on whether it wants to see the effects of commits while it's in progress.
        regards, tom lane