Re: transaction_isolation vs. default_transaction_isolation - Mailing list pgsql-hackers

On Mon, 2009-10-12 at 22:22 -0700, Jeff Davis wrote:
> On Mon, 2009-10-12 at 22:13 -0700, Josh Berkus wrote:
> > However, for *two* settings, and two settings only, we distinguish that
> > by naming an identical setting "default_*" in postgresql.conf.  This is
> > confusing and inconsistent with the rest of the GUCS.  Namely:
> > 
> > default_transaction_isolation
> > default_transaction_read_only
> 
> I think they are named "default_" because whatever you specify at the
> beginning of a transaction overrides the GUC.
> 
> For example, in:
>   BEGIN TRANSACTION ISOLATION LEVEL READ COMMITTED;
>   SET default_transaction_isolation=serializable;
>   ...
> 
> the "default_" makes it more clear which setting overrides the other.

Yeah, they basically have semantics specified by the SQL standard that
are not compatible with anything else in GUC land.  They are more like
SET LOCAL settings, but again not quite.