James Sleeman wrote: > What it means to you as a developer is essentially that however many queries > you do inside a > <CFSTRANSACTION></CFTRANSACTION> > block they will ALL be executed at the same time (well, they won't > strictly, but it will look that way to you). Generally you use them to > maintain database & query integrit, think of this (most common) example... > > You have two processes, both are trying to insert into a database table, > before they do they must figure out what the next "key" value to use is but > querying the database, adding to the key it got from the query and using > that in the insert... each process looks like tihs. > > Query 1 - get key > Add to key > Query 2 - insert record using key > > Now let's say process one comes in, it runs query 1 and adds to the key, > then the task scheduler kicks in, switches out process one and switches in > process two, process two runs query 1 and adds to the key - but because > process one hasn't yet run query 2, process two has calculated the same key > as process one ! One of those processes has to fail now because you can't > have the same key twice. > > If this was wrapped in a transaction then Query 1 and Query 2 would be > grouped togethor, we are assured that they execute "at the same time" and > thus there is no way process two can get the same key as process one.
But only if you set the Isolation Level high enough. IIRC this requires a "Serializable" isolation level. Jochem ______________________________________________________________________ This list and all House of Fusion resources hosted by CFHosting.com. The place for dependable ColdFusion Hosting. FAQ: http://www.thenetprofits.co.uk/coldfusion/faq Archives: http://www.mail-archive.com/[email protected]/ Unsubscribe: http://www.houseoffusion.com/index.cfm?sidebar=lists
