GROQ query to expand references and filter

This is useful to pre-filter references, or count references based on a query like status == 'active'.

Query

*[_type == 'collection'] {
  "numTotalProducts": count(products),
  "numActiveProducts": count((products[]->store.status)[@ == 'active'])
}

In the query above, `products` is an array of references. Therefore, you need to expand them to filter through them.

I've discovered that wrapping a section that expands a reference in parentheses, allows you to filter using regular GROQ brackets. This is not mentioned in the documentation, so I thought I'd share this as a snippet.

Not working: `products[]->store.status[@ == 'active']`

When you query this, you'll find an array is returned with `[null, null, null]`.

Working: `(products[]->store.status)[@ == 'active']`

This will return a properly filtered array of `['active', 'active']`. I use that to `count` the number of active products.

Query

Contributor