PostGraphile's schema generator is built from a number of Graphile Engine plugins. You can write your own plugins - either using the helpers available in graphile-utils, or using the raw plugin interface available from Graphile Engine.

If you're looking for an easy way to remove/rename things, check out smart comments.

Writing Plugins

We've created a number of plugin helpers for common tasks:

• To add new fields and types, check out makeExtendSchemaPlugin
• To change how fields and types are automatically named, check out makeAddInflectorsPlugin
• To change how fields are resolved, check out makeWrapResolversPlugin
• To make certain fields nullable or non-nullable, check out makeChangeNullabilityPlugin
• To process the generated schema, for example to run it through a third-party tool such as graphql-shield, check out makeProcessSchemaPlugin

For everything else, you can write raw Graphile Engine plugins.

Do check out our plugin gallery for examples of plugins. These are generally suitable for copying/pasting into your app and then customising to your needs.

Loading Plugins

Once you've written (or installed) a schema plugin, you can load it using the CLI:

# For a local file:
postgraphile \
  --append-plugins `pwd`/add-http-bin-plugin.js \
  -c postgres:///mydb

# Or, for an npm plugin:
postgraphile \
  --append-plugins postgraphile-plugin-connection-filter \
  -c postgres:///mydb

The --append-plugins option accepts a comma separated list of module specs. A module spec is the absolute path to a JS file to load (or name of an npm module), optionally followed by a colon and the name of the export (you must omit this if the function is exported via module.exports = function MyPlugin(...){...}). E.g.

• --append-plugins my-npm-module (requires module.exports = function NpmPlugin(...) {...})
• --append-plugins /path/to/local/module.js:MyPlugin (requires exports.MyPlugin = function MyPlugin(...) {...})

If you're using postgraphile as a library you can instead use the appendPlugins option which you should pass an array of plugin functions (you are responsible for importing these functions yourself).

const ConnectionFilterPlugin = require("postgraphile-plugin-connection-filter");
//...
app.use(
  postgraphile(process.env.DATABASE_URL, "app_public", {
    appendPlugins: [
      ConnectionFilterPlugin,
      /* add any more plugins you need here */
    ],
    graphiql: true,
  })
);
//...

Remember: multiple versions of graphql in your node_modules will cause problems; so we strongly recommend using the graphql object that's available on the Build object (second argument to hooks) rather than requiring your own version.