Out of the box, PostGraphile supports rudimentary filtering on connections using a condition argument. This allows you to filter for specific values (e.g. username: "Alice" or category: ARTICLE).

It's important when implementing filters to keep performance in mind, so PostGraphile gives you the ability to omit certain fields from the list of filters using the @omit filter smart comment. You may also use the --no-ignore-indexes option to try and automatically omit fields that don't appear to be indexed.

Advanced filtering

You can extend PostGraphile's schema with more advance filtering capabilities by adding fields using custom queries, computed columns or by using makeExtendSchemaPlugin.

You can also augment PostGraphile's existing connections using custom Graphile Engine plugins, such as:

Filter Plugin

A very popular plugin is Matt Bretl's connection-filter plugin, located at https://github.com/graphile-contrib/postgraphile-plugin-connection-filter. This adds a filter argument to connections that enables you to use advanced filters, including filtering on related records from other tables, using greater than, less than and ranges for filtering, and even filtering against the output of functions. If you need advanced filtering in your GraphQL API (and you can use something like persisted queries to prevent malicious parties issuing complex requests) then I recommend you check it out!

Other plugins

Some more of the community plugins relate to filtering, you can read more about them on the community plugins page