What happens inside of a nested transaction, assuming we do have those evenually ... ?
On Mon, 29 Apr 2002, Tom Lane wrote: > Hannu Krosing <[EMAIL PROTECTED]> writes: > > Perhaps we could do > > SET SET TO LOCAL TO TRANSACTION; > > Which would affect itself and all subsequent SET commands up to > > SET SET TO GLOBAL; > > or end of transaction. > > This makes my head hurt. If I do > > SET foo TO bar; > begin; > SET SET TO GLOBAL; > SET foo TO baz; > SET SET TO LOCAL TO TRANSACTION; > end; > > (assume no errors) what is the post-transaction state of foo? > > What about this case? > > SET foo TO bar; > begin; > SET SET TO GLOBAL; > SET foo TO baz; > SET SET TO LOCAL TO TRANSACTION; > SET foo TO quux; > end; > > Of course this last case also exists with my idea of a LOCAL SET > command, > > SET foo TO bar; > begin; > SET foo TO baz; > LOCAL SET foo TO quux; > -- presumably SHOW foo will show quux here > end; > -- does SHOW foo now show bar, or baz? > > Arguably you'd need to keep track of up to three values of a SET > variable to make this work --- the permanent (pre-transaction) value, > to roll back to if error; the SET value, which will become permanent > if we commit; and the LOCAL SET value, which may mask the pending > permanent value. This seems needlessly complex though. Could we get > away with treating the above case as an error? > > In any case I find a LOCAL SET command more reasonable than making > SET's effects depend on the value of a SETtable setting. There is > circular logic there. If I do > > begin; > SET SET TO LOCAL TO TRANSACTION; > end; > > what is the post-transaction behavior of SET? And if you say LOCAL, > how do you justify it? Why wouldn't the effects of this SET be local? > > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED]) > ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
