Filter objects using relationship not querying whole DB in Flask SQLAlchemy

Question

I have two related objects: Post and Comment. One Post can have many Comments. Im using backref so I can reference comment list from post object:

post = Post.query.get(post_id)
all_comments = post.comments # returns all comments of whole post

Now I want to filter those comments by their author. I want to be able to do something like this:

post.comments.filter(author_id=author_id)

In Django I did it like this:

post.comments.all().filter(author_id=author_id)

But in Flask I can't figure it out. I don't to query all database using:

Comment.query.filter_by(post_id=post_id, author_id=author_id)

How do I do that query?

It's not pretty but it's the same thing, you're still querying "all the database" in Django. Just make sure that your Comment tables has indexes on both post_id and author_id — Alex Hall, Mar 25 '20 at 11:25
have you tried `post.comments.filter_by(author_id=author_id)`? — lalithkumar, Mar 25 '20 at 11:27
@AbhishekKulkarni Get all comments that were created by person of id equal author_id, because post can have multiple comments created by different users. — ofca1234, Mar 25 '20 at 11:34

score 0 · Answer 1 · answered Mar 25 '20 at 11:42

0

Try this below :

Comment.query.join(Post, Comment.post_id == Post.id).filter_by(Post.post_id=post_id, Comment.author_id=author_id).all()

answered Mar 25 '20 at 11:42

Abhishek Kulkarni

1 Answers1