[source, ruby]
----
response = client.search(
  body: {
    query: {
      match: {
        city: 'madrid'
      }
    },
    aggregations: {
      tags: {
        significant_terms: {
          field: 'tag',
          background_filter: {
            term: {
              text: 'spain'
            }
          }
        }
      }
    }
  }
)
puts response
----
