Detect Scaling Issues When Loading Data In a GraphQL API

Cache Database Requests Across GraphQL Resolvers

Batch Database Requests with a GraphQL API

Refactor the Data Loader into a Reusable Class

Create a New Cache on Every GraphQL Request Using Apollo Context

Install the DataLoader Package

Fetching an Item by ID with a GraphQL DataLoader

Fetching Many Items by Key with GraphQL DataLoaders

Count the Items in a Collection By Reusing a Data Loader

Count the Items in a Collection with a Custom Data Loader

Use GraphQL Data Loaders to Prevent Scaling Issues by Batching & Caching Database Requests

The simplest way to count the comments on a post is to use a Data Loader that returns all of the comments and return the length.

As long as the primary access pattern is to always fetch the number of comments along with the comments themselves, the Data Loader will batch them together and you'll get the count for free with no extra database requests.

https://app.egghead.io/api/v1/lessons/apollo-count-the-items-in-a-collection-by-reusing-a-data-loader/subtitles

Instructor: [0:02] If we want to count the comments for each post, the simplest way is to reuse our existing commentLoader and simply grab the length of the array that it returns. Let's add that to the schema, returning Int, and then test the query out. Getting a few zeros and a five, so the count is being returned correctly.

[0:26] If we are always going to query both commentCount and the list of comments at the same time, the DataLoader will batch them together, and we can essentially get the count for free with no extra database requests, which makes this the most efficient way to do it.

Count the Items in a Collection By Reusing a Data Loader

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Use GraphQL Data Loaders to Prevent Scaling Issues by Batching & Caching Database Requests