Kevin Grittner wrote:
> Management has simply given a mandate that the software be independent
> of OS and database vendor, and to use Java to help with the OS independence.
> ... we write all of our queries in ANSI SQL in our own query tool, parse it,
> and generate Java classes to run it.
A better solution, and one I've used for years, is to use OS- or database-specific features, but carefully encapsulate
themin a single module, for example, "database_specific.java".
For example, when I started supporting both Oracle and Postgres, I encountered the MAX() problem, which (at the time)
wasvery slow in Postgres, but could be replaced by "select X from MYTABLE order by X desc limit 1". So I created a
function,"GetColumnMax()" that encapsulates the database-specific code for this. Similar functions encapsulate and a
numberof other database-specific optimizations.
Another excellent example: I have a function called "TableExists(name)". To the best of my knowledge, there simply is
noANSI SQL for this, so what do you do? Encapsulate it in one place.
The result? When I port to a new system, I know exactly where to find all of the non-ANSI SQL. I started this habit
yearsago with C/C++ code, which has the same problem: System calls are not consistent across the varients of Unix,
Windows,and other OS's. So you put them all in one file called "machine_dependent.c".
Remember the old adage: There is no such thing as portable code, only code that has been ported.
Cheers,
Craig