Re: Nested Transactions, Abort All

Thomas Swan wrote:
> Alvaro Herrera wrote:
> 
>> Yes, I was thinking about this because the current code behaves wrong if
>> a BEGIN is issued and not inside a transaction block.  So we'd need to
>> do something special in SPI -- not sure exactly what, but the effect
>> would be that the function can't issue BEGIN at all and can only issue
>> SUBBEGIN.
>>
> Isn't this counterintuitive.   It seems that BEGIN and COMMIT/ABORT 
> should be sufficient regardless of the level.  If you are inside a 
> current transaction those commands start a new transaction inside of the 
> current transaction level, just like pushing on and popping off elements 
> on a stack. 

How about this radical idea: Use SAVEPOINT to begin a subtransaction 
and ROLLBACK TO SAVEPOINT to abort that subtransaction. Normally, in 
Oracle, I would write code like:

SAVEPOINT foo;

<do work>

IF (error) THEN ROLLBACK TO SAVEPOINT foo;
END IF;

Could we not treat a subtransaction as an "anonymous" savepoint 
until savepoints are added? So the above in PostgreSQL would read:

SAVEPOINT;

<do work>

IF (error) THEN ROLLBACK TO SAVEPOINT;
END IF;

My old SQL3 draft EBNF reads:

<savepoint statement> ::= SAVEPOINT <savepoint specifier>

<savepoint specifier> ::=      <savepoint name>    | <simple target specification>

<savepoint name> ::= <identifier>

and

<rollback statement> ::=    ROLLBACK [ WORK ] [ AND[ NO ]  CHAIN ]      [ <savepoint clause> ]

<savepoint clause> ::=    TO SAVEPOINT <savepoint specifier>

Mike Mascari