Composite Keys - How?

[bradford]

I believe someone asked this question about a month ago, but I still
need help with this. How do I do composite keys in lift? I have two
classes: Foo and Bar. Now, I want a class called FooBar that links
the two together. I have two objects extending MappedLongForeignKey:
fooId and barId. How do I make these a composite key of FooBar?

Would something like this work?:

def primaryKeyField = (fooId, barId)

[David Pollak]

Take a look at MappedPassword for ways to combine multiple database
columns into a a single lift Mapper field.

[bradford]

I'm extremely new to scala and lift (second day using both). I'm
looking to generate something like the SQL code below. Is this what
MappedPassword.scala is doing?

CREATE TABLE FooBar
(
fooId long NOT NULL
barId long NOT NULL
FOREIGN KEY ( fooId ) REFERENCES Foo ( id )
FOREIGN KEY ( barId ) REFERENCES Bar ( id )
PRIMARY KEY ( fooId, barId )
INDEX ( fooId, barId )
);

[David Pollak]

bradford wrote:

I'm extremely new to scala and lift (second day using both).  I'm
looking to generate something like the SQL code below.  Is this what
MappedPassword.scala is doing?
  

MappedPassword is a single field that represents two columns in the database.

I know you're new to lift and Scala and I'd really like to offer you a nice present by writing the code, but I'm kinda swamped right now and I've got a few other things on my "lift newbies" stack, so I can't commit to working on an example in the next two weeks.  I'm very sorry.

I know Steve Yen was looking into this a few weeks back.  Perhaps he's got an implementation for us.

[bradford]

After reading more about this online, it seems that ORMs have a
difficult time mapping to composite keys. So, if the above is not
possible, would creating FooBar to have an autonumber/serial primary
key with fooId and barId as foreign keys that are unique together work
the same/better? This may be what MappedPasswords is doing??

CREATE TABLE FooBar
(
id serial NOT NULL,
fooId long NOT NULL,
barId long NOT NULL,
FOREIGN KEY ( fooId ) REFERENCES Foo ( id ),
FOREIGN KEY ( barId ) REFERENCES Bar ( id ),
PRIMARY KEY ( id )
);

CREATE UNIQUE INDEX index_name ON FooBar (fooId, barId);

[David Pollak]

bradford wrote:

After reading more about this online, it seems that ORMs have a
difficult time mapping to composite keys.  So, if the above is not
possible, would creating FooBar to have an autonumber/serial primary
key with fooId and barId as foreign keys that are unique together work
the same/better?  This may be what MappedPasswords is doing??

CREATE TABLE FooBar
(
  id serial NOT NULL,
  fooId long NOT NULL,
  barId long NOT NULL,
  FOREIGN KEY ( fooId ) REFERENCES Foo ( id ),
  FOREIGN KEY ( barId ) REFERENCES Bar ( id ),
  PRIMARY KEY ( id )
  

);

class FooBar extends LongKeyedMapper[FooBar] {
  def getSingleton = FooBar
  def primaryKeyField = id
 
  object id extends MappedLongIndex(this)
  object foo extends MappedLongForeignKey(this, Foo)
  object bar extends MappedLongForeignKey(this, Bar)
}

object FooBar extends FooBar with LogKeyedMetaMapper[FooBar] {
  def dbIndexes = Index(foo, bar) :: super.dbIndexes
}

[bradford]

Yes. Thanks for the hard work that you've put into lift. I will keep
working on this and also wait on Steve Yen.

Thanks