Hi Stephan,
On 9 Nov, Stephan Szabo wrote:On Fri, 7 Nov 2003 [EMAIL PROTECTED] wrote:What I meant was not subtransactions or savepoints, but the funny
Whenever an error occurs within the transaction, PostgreSQL puts the whole transaction in an *ABORT* state, so that there is no difference at all between COMMITing or ROLLBACKing it. Even commands successfully carried out before the error ocurred are rolled back, even if I COMMIT the transaction, where no error message whatsoever is shown.
In PostgreSQL all errors are currently considered unrecoverable, and all statements in a transaction must commit or rollback together as a single unit. In the future an implementation of nested transactions or savepoints would presumably relax this limitation to only the successfully committed subtransactions or statements that were not separately rolled back to a previous savepoint.
behaviour that operations already successfully carried out never will be
committed, just because some other operation later within the same
transaction fails. This is far different from the behaviour of all other
DMBS I know. Why not:
Why is that "funny behaviour" for you? By putting the statements into a transaction block you told the data management system "I want this group of statements to be atomic". Atomic means all or nothing. It might not be exactly what you intended to say, and you have a point if you conclude that PostgreSQL is limited because it doesn't let you say anything in between all or nothing. But after all, thus far it is only doing what you asked for.
Jan
begin work; insert into x values (1, 'hi'); --> success insert into x values (1, 'there'); --> failure due to primary key violation insert into x values (2, 'foo'); --> success commit work;
and have two new tuples in the table? Why do _all_ of these operations have to be rolled back? I just don't get it that this has anything to do with savepoints or so. I don't see any problem with an error being recoverable, because the second insert failed and does not have to be recovered while the first and the third worked fine and does not have to be recovered either. When committing a transaction the effects of all operations that did not fail will be made permanent. This is how transaction processing is described in the literature.
If a programmer wants the whole transaction to fail because one part failed, (s)he can always program a rollback in case of at least one error. But there should always be a difference between a rollback and a commit, after at least one statement changing data has reported a success.
Hopefully this can be cleared and perhaps improved within PostgreSQL. Otherwise, PostgreSQL always claims to be close to standards.
Sincerely,
Holger
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