Question

I’m trying to build a forum like platform on GAE.

I must mention first: I’m a bit new to GAE.

I want to pull all replies to a specific post.
So far the structure looks like so:

- Forum
--- Post
----- Reply ( = Post with Post as a parent )

Replies are just posts with post as their parent(instead of the forum as a parent).

The problem begins when I try to pull out all of the replies, the returned results include the ancestor itself.

How can I achieve the same without the ancestor itself?(Might need to mention also that I searched for a solution but haven’t found one)

Edit:

My query is like so:

replies = db.GqlQuery("SELECT * FROM Post WHERE ANCESTOR IS :1", post)

Thanks!

Update:

Well I’ve found a way:

db.GqlQuery("SELECT * FROM Post WHERE ANCESTOR IS :1 AND __key__ != :2", post, post.key())

just query and rule out the ancestor itself in the where clause!

Answer 1

Your proposed solution uses an inequality filter in the query. Inequality filters aren’t supported by the underlying datastore, and are internally translated into two separate queries, like so:

SELECT * FROM Post WHERE ANCESTOR IS :1 AND __key__ < :2
SELECT * FROM Post WHERE ANCESTOR IS :1 AND __key__ > :2

Obviously, this is substantially less efficient. A much simpler and more efficient option is to simply fetch all results, then discard the one entity that you don’t want.