Re: [HACKERS] Nested Transactions, Abort All

[Mike Mascari]

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



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