On 12/15/99 4:46 PM, George Runyan at grunyan@emerging.com wrote:

why does zope use specific DA's instead of a common bridge like JDBC? I was apart of a web logic presentation a few weeks ago and alot of the developers liked the fact that a) they rewrote the socket/rmi api (it multiplexes n requests over a single socket), b) jdbc (of course!) exists and we could 'move this from platform to platform' and not break anything, c) scalability and clustering methods (they use master/slave stubs) which seems to be much more complex than ZEO- but it load balances at the service layer. any comments?

Well, first off, JDBC is Java-specific, hence Java Data Base Connection :-) That makes it of no use for anything not written in Java. RMI is the same thing. The question, however, is similar to the one asked vis-a-vis using ODBC v. native drivers, and I'll frame it that way. The major advantage of using ODBC from an application perspective is that you gain some level of "independence" from a specific database, allowing you to move from Access to SQL Server to DB2 as you change requirements. This is of course a "red herring," in that there is more to databases than just the adapter you talk to. SQL syntax can change dramatically, things like stored procedures, BLOB support, etc., are hugely different and ODBC doesn't deal with that. We tried using Access to prototype databases on the desktop that were going to go to Oracle/Sybase at some point, and found that most things broke because of simple differences. Having said that, we do provide this abstraction, which is that the Connection object is the only thing dependent on the database. SQLMethods are not dependent on the database under them unless you choose to make them. Unfortunately, the world isn't nearly as "standards based" as people would like you to believe. So assuming you buy into the "advantage," why would you forsake this panacea for the nightmare of "database specific" adapters? Well, one it lets you gain better performance by removing at least one layer of code off the system. Second, ODBC (and JDBC) are least common denominators, and while they provide some level of abstraction, often it's missing core pieces that people would like to use. Additionally, ODBC drivers on anything but NT are not common, often extra-cost and largely unused, therefore potentially buggy, and therefore we'd be forsaking the entire UNIX arena (which represents most of our customer base) by buying into what is effectively a Windows strategy. Also, on platforms like Oracle, the ODBC drivers are notoriously bad.

but I am interested in the jdbc vs. custom built DA's

This is just my view, but the JDBC comparison is not terribly viable given we don't use Java. Chris -- | Christopher Petrilli Python Powered Digital Creations, Inc. | petrilli@digicool.com http://www.digicool.com