Add filtering option to the graphql paginated query - reactjs

Question

I am using this nice apollo-universal-starter-kit in one of my projects. I have a task to add a filtering option to this page to filter posts that have more than 2 comments.
The starter kit uses Apollo graphql-server as the back-end. The schema description for the posts looks like this:
# Post
type Post {
id: Int!
title: String!
content: String!
comments: [Comment]
}
# Comment
type Comment {
id: Int!
content: String!
}
# Edges for PostsQuery
type PostEdges {
node: Post
cursor: Int
}
# PageInfo for PostsQuery
type PostPageInfo {
endCursor: Int
hasNextPage: Boolean
}
# Posts relay-style pagination query
type PostsQuery {
totalCount: Int
edges: [PostEdges]
pageInfo: PostPageInfo
}
extend type Query {
# Posts pagination query
postsQuery(limit: Int, after: Int): PostsQuery
# Post
post(id: Int!): Post
}
postsQuery is used to generate a paginated result of the posts
Here is how postsQuery resolves (complete code here)
async postsQuery(obj, { limit, after }, context) {
let edgesArray = [];
let posts = await context.Post.getPostsPagination(limit, after);
posts.map(post => {
edgesArray.push({
cursor: post.id,
node: {
id: post.id,
title: post.title,
content: post.content,
}
});
});
let endCursor = edgesArray.length > 0 ? edgesArray[edgesArray.length - 1].cursor : 0;
let values = await Promise.all([context.Post.getTotal(), context.Post.getNextPageFlag(endCursor)]);
return {
totalCount: values[0].count,
edges: edgesArray,
pageInfo: {
endCursor: endCursor,
hasNextPage: values[1].count > 0
}
};
}
And, here is a graphql query which is used on the front-end with React post_list component (complete code for the component is here)
query getPosts($limit: Int!, $after: ID) {
postsQuery(limit: $limit, after: $after) {
totalCount
edges {
cursor
node {
... PostInfo
}
}
pageInfo {
endCursor
hasNextPage
}
}
}
This was a long introduction :-), sorry
Question:
How can I add filtering option to the post_list component/page? I kind of understand the React side of the question, but I do not understand the graphql one. Should I add a new variable to the postsQuery(limit: $limit, after: $after) so it looks like postsQuery(limit: $limit, after: $after, numberOfComments: $numberOfComments)? And then somehow resolve it on the back-end? Or, I am on the wrong track and should think in the different direction? If so, can you point me to the right direction? :-)
Thank you in advance!

Answer 1

IMO I would definitely solve this on the backend. As far as whether or not it should be a new variable, i personally would say yes, and your Post.getPostsPagination could be updated to support filtering on comment count, ideally you want that as part of the DB request so that you know you are getting N number of the types of posts you want, otherwise it will open up the door for edgecases in your pagination.
The other option is a new query for CuratedPosts, or FilteredPosts, or whatever you want to call it that already knows to filter based on number of comments.