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.