Re: Comparison of PGSQL and DB2
От | Robert Treat |
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Тема | Re: Comparison of PGSQL and DB2 |
Дата | |
Msg-id | 1079030391.2753.601.camel@camel обсуждение исходный текст |
Ответ на | Re: Comparison of PGSQL and DB2 (Josh Berkus <josh@postgresql.org>) |
Ответы |
Re: Comparison of PGSQL and DB2
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Список | pgsql-advocacy |
On Tue, 2004-03-09 at 13:22, Josh Berkus wrote: > Shashank: > > What follows is my reply to IBM's 2-year-old feature comparison of PostgreSQL > and DB2. Each of the entries is an item that DB2 has and claims that > PostgreSQL does not. I've put my replies to these claims. > <snip> > > > Isolation Levels > > (Support all four ANSI isolation levels (UR, CS, RS, RR).) > > I'm not sure about this one; I suspect that we do, however, since MVCC, > invented for the Postgres Project, has become a standard for transaction > isolation in the database industry. > Not exactly sure which acronyms above correspond to which levels (as I know them by different names apparently) but we support Read Committed and Serializable levels, which are by far the most common of the two AFAIK. The others as I know them are Read Uncommitted aka phantom reads, and Repeatable Read, which we do not support. Of course we also supply a extensive locking methods for further control. More info on our isolation levels can be found at http://www.postgresql.org/docs/7.4/static/transaction-iso.html <snip> > > Federated Database Support > > (Ability to allow applications to access & perform JOIN operations on > multiple disparate databases.) > > This is a feature which we do not have because it violates the ANSI SQL > Specification. > Perhaps worth a mention that using dblink, you can actually make functionality similar to this. I have recently been experimenting with using views calling dblink functions to create "local tables" that really live in a separate database on a completely separate machine. I don't know if I would recommend the technique but I think the capabilities are there. Robert Treat -- Build A Brighter Lamp :: Linux Apache {middleware} PostgreSQL
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