I am confused on the use of session.filter to query a collection.

I have a class, Animal, that has a collection of Tattoos. I want to execute a query that selects animals based on the value of the tattoo (tattoo has several properties, value, location, etc.). Session.filter sounds like what I want, except the first parameter to the method is the collection and I am not sure where I obtain the collection from. Do I have to query all animals first (there are no other limiting criteria on the animals selected so I would select every animal in the database!) and then loop through the list of animals calling session.filter for each?

I am hoping to use session.filter to select only animals with a certain tattoo. In essence the SQL I need to end up with is:

eh? Why do you think you want to use a filter instead of just an ordinary query?

Um, because what I want to query on is a property of an element of a collection. While searching the forum for how to do this I saw some similar scenarios where people were directed to use session.filter and referring to the docs, the example in section 7.3.4 of the docs does seem to be exactly what I want to do...?

You use a join for this.

Really?! Damn I feel like an idiot.

What is session.filter for then?

For when you do have a collection ;)

Gavin! LOL! I think I am going crazy - don't I have a collection in my example?!? I think I do, Animal has a collection of Tattoos.....?! :) Or don't I understand collections either?! ;)

its for when you want to do:

Yes, that is exactly what I want to do! Maybe the SQL I put in my initial post caused some confusion. But I realize now I need to provide selection criteria on not only the animal's tattoo collection but properties on animal itself as well (like sex or breed), and it doesn't look like session.filter lets me query on anything but the collection.