GraphQL tutorial for LessWrong and Effective Altruism Forum

riceissa8 Dec 2018 19:51 UTC
102 points
8 comments5 min readLW link

This post is a tutorial on using GraphQL to query for information about LessWrong and the Effective Altruism Forum. It’s mostly intended for people who have wanted to explore LW/​EA Forum data but have found GraphQL intimidating (this was the case for myself until several weeks ago).

General steps for writing a query

(This section will make more sense if you have seen some example queries; see next section.)

For the queries that I know how to do, here is the general outline of steps:

  1. Go to https://​​www.lesswrong.com/​​graphiql or https://​​forum.effectivealtruism.org/​​graphiql depending on which forum you want to query data for.

  2. Figure out what the output type should be (e.g. comments, comment, posts, post).

  3. Type {output_type(input)} into GraphiQL and hover over input.

    Here is what it looks like for the comment output type:

    Here is what it looks like for the comments output type:

  4. Click on the type that appears after input (e.g. MultiCommentInput, SingleCommentInput). A column on the right should appear (if it was not there already). Depending on the fields listed in that column, there will now be two ways to proceed. (Generally, it seems like singular output types (e.g. comment) will have selector and plural output types (e.g. comments) will have terms.)

    Here is what it looks like for the comment output type. In the image, I have already clicked on SingleCommentInput so you can see selector under the documentation (rightmost) column.

    Here is what it looks like for the comments output type. Again, in this image, I have already clicked on MultiCommentInput so you can see terms under the documentation (rightmost) column.

    In the fields listed, if there is selector (e.g. for comment):

    • Click on the selector type (e.g. CommentSelectorUniqueInput). Use one of the fields (e.g. _id) to pick out the specific item you want.

      Here is what you should click on:

      What it looks like after you have clicked:

    If there is terms (e.g. comments):

    • Go to the collections directory in the LessWrong 2.0 codebase, and find the views.js file for your output type. For example, if your output type is comments, then the corresponding views.js file is located at collections/comments/views.js.

    • Look through the various “views” in the views.js file to see if there is a relevant view. (There is also a default view if you don’t select any view.) The main things to pay attention to are the selector block (which controls how the results will be filtered) and the options block (which mainly controls how the results are sorted).

    • Pass in parameters for that view using keys in the terms block.

  5. Start a results block, and select the fields you want to see for this output type. (If you don’t select any fields, it will default to all fields, so you can do that once and delete the fields you don’t need.)

Examples

I’ve built a sample interface for both LessWrong and EA Forum that allows an easy way to access the queries used to generate pages:

By passing format=queries in the URL to any page, you can view the GraphQL queries that were made to generate that page. Rather than showing many examples in this post, I will just show one example in this post, and let you explore the reader.

As an example, consider the page https://​​eaforum.issarice.com/​​?view=top. Clicking on “Queries” at the top of the page takes you to the page https://​​eaforum.issarice.com/​​?view=top&offset=0&before=&after=&format=queries Here you will see the following:

    {
      posts(input: {
        terms: {
          view: "top"
          limit: 50
          meta: null  # this seems to get both meta and non-meta posts



        }
      }) {
        results {
          _id
          title
          slug
          pageUrl
          postedAt
          baseScore
          voteCount
          commentsCount
          meta
          question
          url
          user {
            username
            slug
          }
        }
      }
    }

Run this query



    {
      comments(input: {
        terms: {
          view: "recentComments"
          limit: 10
        }
      }) {
        results {
          _id
          post {
            _id
            title
            slug
          }
          user {
            _id
            slug
          }
          plaintextExcerpt
          htmlHighlight
          postId
          pageUrl
        }
      }
    }

Run this query

Clicking on “Run this query” (not linked in this tutorial, but linked in the actual page) below each query will take you to the GraphiQL page with the query preloaded. There, you can click on the “Execute Query” button (which looks like a play button) to actually run the query and see the result.

I should note that my reader implementation is optimized for my own (probably unusual) consumption and learning. For article-reading and commenting purposes (i.e. not for learning how to use GraphQL), most users will probably prefer to use the official versions of the forums or the GreaterWrong counterparts.

Tips

  • In GraphiQL, hovering over some words like input and results and then clicking on the resulting tooltip will show the parameters that can be passed to that block.

  • Forum search is not done via GraphQL. Rather, a separate API (the Algolia search API) is used. Use of the search API is outside the scope of this tutorial. This is also why the search results page on my reader (example) has no “Queries” link (for now).

  • For queries that use a terms block: even though a “view” is just a shorthand for a selector/​options pair, it is not possible to pass in arbitrary selector/​options pairs (due to the way security is handled by Vulcan). If you don’t use a view, the default view is selected. The main consequence of this is that you won’t be able to make some queries that you might want to make.

  • Some queries are hard/​impossible to do. Examples: (1) getting comments of a user by placing conditions on the parent comment or post (e.g. finding all comments by user 1 where they are replying to user 2); (2) querying and sorting posts by a function of arbitrary fields (e.g. as a function of baseScore and voteCount); (3) finding the highest-karma users looking only at the past days of activity.

  • GraphQL vs GraphiQL: /graphiql seems to be endpoint for the interactive explorer for GraphQL, whereas /graphql is the endpoint for the actual API. So when you are actually querying the API (via a program you write) I think you want to be using https://​​www.lesswrong.com/​​graphql and https://​​forum.effectivealtruism.org/​​graphql (or at least, that is what I am doing and it works).

Acknowledgments

Thanks to:

  • Louis Francini for helping me with some GraphQL queries and for feedback on the post and the reader.

  • Oliver Habryka for answering some questions I had about GraphQL.

  • Vipul Naik for funding my work on this post and some of my work on the reader.

riceissa8 Dec 2018 19:51 UTC
102 points
8 comments5 min readLW link