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Re: [stellation-res] Database abstraction
Have you taken a look at the Torque project?  http://jakarta.apache.org/turbine/torque/   They deal with a lot of these issues .. Maybe you can reuse some of their stuff.

Mike

Mark C. Chu-Carroll wrote:
On Tuesday 13 August 2002 06:37 pm, Marco Qualizza wrote:
  
Without being too critical, I don't think that you're being abstract
enough.  ie/  It looks like you're trying to rebuild the String with
method calls, instead of, for example, just creating a
ForeignConstraint object and having a
addConstraint(ForeignConstraint constraint)...
    
I did consider that... Before I went all out and went to that level of
abstraction, I wanted to be sure that this general approach of 
abstracting out to command objects that mask the underlying SQL
wasn't totally insane. (I'm working today in the pattern of 5 minutes
of hacking, five minutes of playing with my sick 2yo daughter, so
I'm never really getting a chance to think all the way through
anything.. So before I blew the rest of the days work on this approach,
I wanted a sanity check.)

	-Mark



  
but that's my $.02 (approx. $.013 after exchange with the States...)

Tuesday, August 13, 2002, 10:06:39 AM, you wrote:
    
So... I'm looking at trying to create a database abstraction layer that
will work accross Postgres, DB2, Oracle, MySQL/InnoDB, and
Firebird.

One option is to totally automate the SQL generation process. This
allows us to smoothly handle things like the INNODB declarations
that need to go onto the end of table creations, variations in typenames,
etc.

I've tried a first cut at doing this for table creation. I'm looking at a
bit of test code, and I can't decide whether I like it (it's nicely
abstract, and quite easy to write), or hate it (it's hard to see the SQL
in it). Here's a sample: what do you folks think: is this a good
direction, or am I being idiotically abstract?

Here's the original SQL:

        CREATE TABLE Properties (INTEGER aid,
                                                INTEGER vid,
                                                INTEGER inheritable,
                                                VARCHAR(200) name,
                                                VARCHAR(1600) value,
                        CONSTRAINT fk3 FOREIGN KEY (aid, vid) REFERENCES
Versions(aid, vid) PRIMARY KEY(aid, vid, name))


Here's the corresponding code:
        DatabaseCreateTableCommand cmd =
                    _db.createTable("Properties")
                        .addIntegerField("aid")
                        .addIntegerField("vid")
                        .addIntegerField("inheritable")
                        .addShortStringField("name")
                        .addLongStringField("value")
                       .beginForeignKeyConstraint("fk3", "FOREIGN KEY")
                            .addConstraintField("aid")
                            .addConstraintField("vid")
                           .beginForeignKeyReferences("Versions")
                             .addConstraintField("aid")
                             .addConstraintField("vid")
                           .endForeignKeyConstraint()
                       .beginPrimaryKeyConstraint()
                          .addConstraintField("aid")
                          .addConstraintField("vid")
                          .addConstraintField("name")
                       .endPrimaryKeyConstraint()
                     .endCommand();
      
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