True, but even an application would need to "undo" in transactions, I'd think. Like, if a user drags a widget from column A to B, it generates an INSERT in one column and a DELETE in another. Pressing Undo once would leave it in both columns, which is probably unexpected.
Anyway, I was more thinking of a "transaction count" sort of variable, indicating how many total transactions have been committed to the database. Just something to group undo log entries by transaction without maintaining a manual transaction identifier. Thanks for considering it! -david Ken wrote: > the Undo/Redo mechanism described is not really for transactions but rather a > "Button" within an application. So that the user can undo/redo changes. > > Only one transaction can be active at a time. So to the best of my knowledge > there is no "transaction number" as there can be only 1. Now you may go ahead > and implement "pseudo transactions" and implement your own transaction > number. etc... > > HTH, > Ken > > > David Barrett <[EMAIL PROTECTED]> wrote: What's the best way to group undo > log entries by transaction? Is there > a function that returns the current transaction number? Or what's the > best way to set a global variable that is inserted into the undo log by > the trigger? > > As background, the wiki has a great page on undo/redo: > > http://www.sqlite.org/cvstrac/wiki?p=UndoRedo > > But unless I misunderstand, it seems that a single transaction will > create multiple entries in the log. For example, a transaction > containing both an insert and a delete will generate two entries in the > undo log. Therefore, to undo that transaction, I need to atomically > commit the "undo" of both the insert and delete in a single transaction. > > That's fine, but the log created by the example doesn't seem to indicate > which group of undo rows correspond to a single transaction. Indeed, > the word "transaction" doesn't even appear in the page. > > Now, digging through the archives I see reference to a "transaction > number" here: > > http://www.mail-archive.com/sqlite-users@sqlite.org/msg23962.html > > Is there any explicit way to get the current transaction number? I was > hoping to see some "transaction_number()" function here, but I don't: > > http://www.sqlite.org/lang_corefunc.html > > If such a function did exist, then I could just update the triggers to > insert that along with the corresponding SQL. > > Lacking that, what's the best way to manually to set some kind of global > variable at the start of each transaction? One way is to maintain a > separate table with a single cell containing the latest transaction > number (which I manually increment at the start of each transaction) and > then just SELECT that in the trigger sub-query, but that seems yucky. > Is there an easier way I'm missing? > > Thanks! > > -david > > > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
