Filtering
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).
See an example using the connection argument.
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 the following:
Filter Plugin
🚨BEWARE🚨: adding powerful generic filtering capabilities to your GraphQL API is strongly discouraged, not just by Benjie (the maintainer of PostGraphile) but also by Lee Byron (one of the inventors of GraphQL) and various other experts in the GraphQL ecosystem. It is strongly advised that you add only very specific filters using one of the techniques above (and that you make their inputs as simple as possible) rather than using a generic filtering plugin like this. Not heeding this advice may lead to very significant performance issues down the line that are very hard for you to dig your way out of.
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!
Be aware that the connection-filter plugin has no live-query specific handling. This means while live queries will work, the filters are not taken into account when checking if the query result changed. This means that you may get a subscription update every time something in the collection changes, even if the result with the applied filter is still the same.
With the included condition filters live queries work as expected until you
start using makeAddPgConditionPlugin to add your own conditions.
Other plugins
Some more of the community plugins relate to filtering, you can read more about them on the community plugins page