Hi ! Dennis Lee Bieber írta: > On Wed, 19 Apr 2006 17:29:28 +0200, Christian Stooker > <[EMAIL PROTECTED]> declaimed the following in comp.lang.python: > > >> Please answer me: it is wrong I write about, or that is seems to be not >> working in SQLite ? >> >> > I don't think the feature you want to use is available -- heck, it > may ONLY be a firebird feature... (I've not seen anything similar in any > of the MySQL back-ends, or if there, I've not encountered it; and there > aren't enough easily read documents for MaxDB [aka SAP-DB] in print to > see if it has such a feature. My MSDE books don't mention it either, so > I suspect M$ SQL Server may not support such). > Sorry, but I don't think that this feature is exists in only Firebird. Good RDMBS systems ***must have*** many transaction isolation levels. The higher isolation level guaranteed a safely view for actual user. READ COMMITTED, and REPEATABLE READ isolation level makes me sure, that if I have a snapshot from the database, I get it same datas *everytime* while my transaction opened. Until trs. is closed and reopened, I can see the new modifications created by another user(s). But when I keep alive my transaction, never I see any modifications, only what I created. In this mode I don't see any user's updates - vainly he or she do many commits (As I see in SQLite, the another user's committed records visible for me - this is corrupting my view !) That is the only way to I get good reports from an invoice manager application, because I see current state of the database - the sum(subtotals) everytime equal with total. In lower isolation level I can see the new committed records - and that is bad thing, because in this time the sum(subtotals) sometimes not equal with total.
That problem is just like thread synch. problem, where I need to protect my subresources with locks/semaphores to avoid corrupting of data. In Delphi I must protect string vars, because when every thread want to write/read from this string, they easily make corrupted string from the source... > SQLite is a "file server" style database; Firebird is a > client/server model. > > In Firebird, the server can track independent connections and > maintain state for each. SQLite runs "locally"; each connection > considers itself to be the only user of the database file (and locking > for updates is on a file basis, not table or record). Once you commit a > transaction in SQLite, the file itself is fully modified, and any other > connections see that modified file -- there is no temporary session > journal for a connection that holds a snapshot of that connection's > data. > So I cannot use a transaction number that identify transactions, and make same isolation effect what I said about before ? Thanx for help: dd -- http://mail.python.org/mailman/listinfo/python-list
