Filtering arrays in a query and using match for comparison in Sanity.io.

You can filter arrays directly within a GROQ projection using bracket notation with a filter condition. For your case with actors and roles, here's how to do it:

*[_type == 'movie']{
  ..., 
  "leadingActors": actors[role == "leading"]
}

The key is placing the filter condition [role == "leading"] directly on the array within your projection. This filters the actors array to only include objects where role equals "leading".

Here are more examples showing different filtering scenarios:

// Filter and project specific fields from the filtered array
*[_type == 'movie']{
  title,
  "leadingActors": actors[role == "leading"]{
    name,
    role
  }
}

// Filter with multiple conditions
*[_type == 'movie']{
  "topActors": actors[role == "leading" && experience > 10]
}

// Filter and follow references in the array
*[_type == 'movie']{
  "leadActors": actors[role == "leading"].person->{
    name,
    bio
  }
}

// Using match for text filtering
*[_type == 'movie']{
  castMembers[characterName match 'Ripley']{
    characterName, 
    person
  }
}

This is documented in the GROQ Query Cheat Sheet under "Object Projections" - specifically the "Filter embedded objects" example. The filter is applied during projection, so it's efficient and only returns the subset of array elements that match your condition.