apollo-link-deep-dedup

A custom Apollo Link library for resolving GraphQL query against cache as much as possible and issuing minimal requests.

Motivation

The implementation of Apollo client results in sending full queries to the server over the network, which can be partially fulfilled by the cached data.

Resolving every query with cached data as much as possible and issuing the minimal request to the server reduces the size of data transferring over the network, and alleviates the query resolution work on the server on an each-query basis.

Features

Apollo client writes the data from every query to the cache as normalized objects. For every query, deepDedupLink

resolves the query against the cache
gets partial results from cache
removes fully-resolved fields from the query
sends query to downstream links (e.g. httpLink for issuing request to the server)
merges partial results from both cache and server
sends full result to upstream links

deepDedupLink deduplicates queries thoroughly. Even with very nested queries, it is able to deduplicate the query at every-field level (see below example).

It currently only supports apollo-cache-inmemory and bypasses deduplication on non-query operations (e.g. mutation and subscription) and fields with directives and fragments.

Example

First query

query {
    authors {
        id
        firstName
        posts {
            id
            votes
        }
    }
    press {
        name
        address
    }
}

Second query without deduplication

query {
    authors {
        id
        firstName
        lastName
        posts {
            id
            votes
            title
        }
    }
    press {
        name
        address
    }
}

Second query with deduplication (the one that gets sent to the server)

query {
    authors {
        lastName
        posts {
            title
        }
    }
}

Installation

npm install @instructure/apollo-link-deep-dedup --save

Usage

import InMemoryCache from 'apollo-cache-inmemory';
import { DeepDedupLink } from 'apollo-link-deep-dedup';

const cache = new InMemoryCache();
const deepDedupLink = new DeepDedupLink({ cache });

Use link with apollo client and other links

import ApolloClient from 'apollo-client';
import InMemoryCache from 'apollo-cache-inmemory';
import { ApolloLink } from 'apollo-link';

// import DeepDedupLink
import { DeepDedupLink } from 'apollo-link-deep-dedup';

// cache used by apollo client
const cache = new InMemoryCache();

// pass in the cache as an option to initialize deepDedupLink
const deepDedupLink = new DeepDedupLink({ cache });

// compose apollo links
const link = ApolloLink.from([
    // ...upstreamLinks,
    deepDedupLink,
    // ...downstreamLinks (e.g. httpLink),
]);

// initialize apollo client with the cache and links
const client = new ApolloClient({
    link,
    cache,
});

Options

deepDedupLink takes an object with one required cache option

cache: the same cache object passed in when initializing ApolloClient

Context

deepDedupLink can be overridden by using the context on a per operation basis:

forceFetch: a boolean (defaults to false) to bypass deduplication per request

// a query with apollo-client that will not be deduplicated
client.query({
    query: MY_QUERY,
    context: {
        forceFetch: true,
    }
});

Development

git clone https://github.com/instructure/apollo-link-deep-dedup.git

npm install
npm run watch

A development guide can be found here.

License

MIT

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