> On Jun 23, 2014, at 3:57 PM, Nikolay Samofatov > <nikolay.samofa...@red-soft.biz> wrote: > > Some records for a join can be read before a transaction is committed, and > some after. Same with EXISTS. It can see different set of commits from the > one when main row was read. > You can see partial commits in results, even inside a single row returned by > the query. > Nobody is ready for this, this is CRAZY, nobody expects this. If this data is > used for any remotely important purpose, you will get whammed.
Right, that's the beauty of read-committed. It's not stable. And, in Firebird, it performs no better than an isolation mode that is stable. So why offer it at all? In both Interbase and NuoDB, major customers to be insisted that in every database they used, they could see new data without starting a new transaction. And that was the way databases behaved. No amount of reference to scholarly literature could convince them in the face their experience. So we put in a bad mode to close big sales. > The fact that inconsistency shows up infrequently, under parallel load and is > not easily > reproducible, sets you up to be eventually burned. And once burned you will > hesitate to trust DMBS that behaves in such ways. And that's the way Oracle, MS SQL and others behaved at the time. > > This is not normal. This is a BUG. > The bug is the existence of read committed. The excuse is compatibility with other databases, If they now offer cursor stabilty, then Firebird should too. If there's a performance cost, make it an option. May I suggest using the word "stability" rather than "sensitivity"? At least to my ear (and feeble brain) sensistivity doesn't suggest seeing changes in route. Stability suggests not seeing concurrent changes. Cheers, Ann > ------------------------------------------------------------------------------ Open source business process management suite built on Java and Eclipse Turn processes into business applications with Bonita BPM Community Edition Quickly connect people, data, and systems into organized workflows Winner of BOSSIE, CODIE, OW2 and Gartner awards http://p.sf.net/sfu/Bonitasoft Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
