Re: BEGIN inside transaction should be an error

On Wed, 2006-05-10 at 21:24 -0400, Tom Lane wrote:
> Martijn van Oosterhout <kleptog@svana.org> writes:
> > How do other database deal with this? Either they nest BEGIN/COMMIT or
> > they probably throw an error without aborting the transaction, which is
> > pretty much what we do. Is there a database that actually aborts a
> > whole transaction just for an extraneous begin?
> 
> Probably not.  The SQL99 spec does say (in describing START TRANSACTION,
> which is the standard spelling of BEGIN)
> 
>          1) If a <start transaction statement> statement is executed when an
>             SQL-transaction is currently active, then an exception condition
>             is raised: invalid transaction state - active SQL-transaction.
> 
> *However*, they are almost certainly expecting that that condition only
> causes the START command to be ignored; not that it should bounce the
> whole transaction.  So I think the argument that this is required by
> the spec is a bit off base.

If you interpret the standard that way then the correct behaviour in the
face of *any* exception condition should be *not* abort the transaction.
In PostgreSQL, all exception conditions do abort the transaction, so why
not this one? Why would we special-case this?

--  Simon Riggs EnterpriseDB          http://www.enterprisedb.com