Re: Phantom Inserts

In article <pwongD4C773.F15@netcom.com>, pwong@netcom.com (Philip S. Wong) writes... . . . > >It seems to me that complete phantom protection would prevent concurrent >inserts in any table that is read by a transaction. Any thoughts? >How do different databases handle this? This is simple and is implemented in Rdb (Oracle Rdb). The first statement is false, concurrent inserts can happen within the table, as long as the first select statement had an access path to fetch the records. [read didn't have to do a sequential scan of the table...in this case the table is the granularity of the concurrency issue]. So say that <condition x> was resolved by some index structure and every query, then to prevent phantoms you just ensure that no <condition x'> can be inserted. This subsets the table in such a ways that conditions x,z... can be inserted. > >BTW, how important is the protection against phantom inserts anyway? >It doesn't seem common in applications that I have seen. A number of our customers find this as critical and since it is hard to do outside the confines of the database system...it is considered a very important feature. -Jay Feenan ********************************************************************* *** Jay Feenan *** *** Oracle Rdb Engineering *** *** *** *** opinions expressed here are solely my own and not those of my *** *** employer. *** *** *** *********************************************************************