Creating a Filter-Only Field

Say you want a dimension which cannot be selected in the UI, but which can be filtered on. This can be done with a clever application of templated filters.

First, we hide the dimension in question using hidden: yes. This means the dimension will not show up in the explore.

dimension: foo {
  type: string
  hidden: yes
  sql: ${TABLE}.foo ;;
}

Now we make a filter field. By itself, a field of type filter does nothing. But combined with templated filters, we can link this filter to our foo dimension.

filter: filter_on_foo {
  type: string
  sql: {% condition filter_on_foo %} ${foo} {% endcondition %} ;;
}

The sql parameter of a filter field applies SQL directly to the WHERE clause of the query. In this case, it’s saying:

take the filter condition specified in the filter_on_foo filter and apply it to the ${foo} dimension.

This way, we can just show users filter_on_foo to let them filter on foo while still keeping foo hidden.