On Feb 20, 2014, at 3:22 PM, Jonathan Vanasco <jonat...@findmeon.com> wrote:
> this seems to work, but I want to just make sure this is the intended > behavior. > > a = dbSession.query( Something ).filter( Something.primary_key == 1 > ).first() > b = dbSession.query( Something ).get( 1 ) > c = dbSession.query( Something ).get( 1 ) > d = dbSession.query( Something ).get( 1 ) > e = dbSession.query( Something ).get( 1 ) > > in the above example , we will only hit the database once , because the > 'filter' populates the local session map with the primary key. right ? yes. As long as you maintain a reference to the object outside of the session. I use this pattern when I am dealing with lots of data that has a bunch of many to ones. Suppose Player objects have a many-to-one to a Sport. We have large N number of players and just a handful of Sports. So i do this: sports = set(sess.query(Sport)) # one SELECT. hold onto “sports” for the duration for player in sess.query(Player): # one SELECT # … player.sport # uses get(), no SELECT this is not too different from using “subquery eager loading” except the queries are straight SELECT with no joins or subqueries.
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