Re: Nested Transactions, Abort All

Alvaro Herrera wrote:

>On Fri, Jul 09, 2004 at 10:38:15AM -0500, Thomas Swan wrote:
>
>  
>
>>visibility issue and how far do you unwind the depth of subtransactions 
>>or transactions?
>>
>>BEGIN
>> UPDATE A
>> SAVEPOINT X
>> BEGIN
>>   BEGIN
>>     UPDATE B
>>     BEGIN
>>       UPDATE C
>>       ROLLBACK TO SAVEPOINT X
>>    
>>
>
>What happens here is that the user will go nuts.  We will have a
>prominent entry in the docs: "using both nested transactions and
>savepoints inside a transaction can cause confusion.  We recommend you
>stick to one or the other."  Or something like that.
>
>(What would really happen: when ROLLBACK TO SAVEPOINT X is executed,
>nested transactions created after the SAVEPOINT will be closed.)
>
>So this is another reason why we should use COMMIT to close a nested
>transaction: it may refer to a transaction that is already closed
>because the user got confused.
>
>  
>
Technically, a ROLLBACK TO SAVE POINT X would be an ABORT on all nested 
transactions.  COMMIT means that if the parent transaction commits then 
the child transaction will also commit.

BEGIN BEGIN   UPDATE A ROLLBACK UPDATE B
COMMIT

The changes from UPDATE A will not commit with the changes from UPDATE B.

BEGIN BEGIN   UPDATE A COMMIT UPDATE B
COMMIT

The changes from UPDATE A will commit with the changes from UPDATE B.

BEGIN BEGIN   UPDATE A COMMIT UPDATE B
ROLLBACK

The changes from UPDATE A will not commit with the changes from UPDATE 
B, and the changes from UPDATE B will not commit either.