More Batching

Batching can also be done through a many-to-many relationship. After the first SQL query, Join Monster will select from the junction table, and then join it on the related table. In addition to the junctionTable, you'll need to specify the junctionTableKey for uniqueness. This can be string for a single unique column or an array for a composite.

const User = new GraphQLObjectType({
  // ...
  fields: () => ({
    following: {
      description: 'Users that this user is following',
      type: new GraphQLList(User),
      // batching many-to-many is supported too
      junctionTable: 'relationships',
      // this table has no primary key, but the combination of these two columns is unique
      junctionTableKey: [ 'follower_id', 'followee_id' ],
      junctionBatch: {
        // the matching column in the junction table
        thisKey: 'follower_id',
        // the column to match in the user table
        parentKey: 'id',
        // how to join the related table to the junction table
        sqlJoin: (junctionTable, followeeTable) => `${junctionTable}.followee_id = ${followeeTable}.id`
      }
    },
  })
})

This introduces another batch to the plan. In addition to the changes made on the previous page, the plan now has 3 database queries.

Requests for the followees and for the comments are independent, and are sent concurrently.