On Wed, 7 Jul 2004, Oliver Jowett wrote:
So how do you propose supporting simple rollback of a subtransaction? It seems like an extension regardless of how it's done.
If I understand you correctly what you want is a ROLLBACK TO SAVEPOINT
foo; followed by a RELEASE SAVEPOINT foo;
Ugh.. nasty syntax and an extra empty transaction.
Also, how do you get an anonymous subtransaction? SAVEPOINT syntax would seem to always require a name.
One of the use cases for subtransactions was to avoid rollback of the entire transaction if there's an error in a single command -- you wrap each command in a subtransaction and roll it back if it fails. If we only have SAVEPOINT syntax this looks like:
-- Success case SAVEPOINT s_12345 INSERT INTO foo(...) VALUES (...) RELEASE SAVEPOINT s_12345
-- Error case SAVEPOINT s_12346 INSERT INTO foo(...) VALUES (...) ROLLBACK TO SAVEPOINT s_12346 RELEASE SAVEPOINT s_12346
-- Repeat ad nauseam
This is pretty ugly. Given that the underlying mechanism is nested subtransactions, why should it be necessary to jump through those sort of hoops to gain access to them?
If you don't like adding extra commands, what about extending the standard transaction control commands ("BEGIN NESTED" etc) instead?
-O
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