Highlighting Fields

To receive ElasticSearch highlights for your matches you need to do the followings:

1. Add highlightedFields under hits for your Searchkit config. Here you may list the name of fields for which you want to get highlights, or an object where you specify the field name and the highlight configuration according to the ElasticSearch highlighting documentation
2. Add a highlight field to your ResultHit graphql schema type
3. When configuring ApolloServer specify a custom resolver for highlight

The following example generates a JSON encoded string version of the highlight objects received from ElasticSearch. You may specify another shape for highlight in your ResultHit type and a matching transformation of hit.highlight in your resolver.

const searchkitConfig = {
  host: 'http://localhost:9200/', // elasticsearch instance url
  index: 'movies',
  hits: {
    fields: [ 'title', 'plot', 'poster' ],
    highlightedFields: [
      'title',
      {
        field: 'plot',
        config: {
          pre_tags: ['<b>'],
          post_tags: ['</b>']
        }
      }
    ]
  },
  query: new MultiMatchQuery({
    fields: [ 'plot','title^4']
  }),
  facets: [
    ...
  ]
}

const { typeDefs, withSearchkitResolvers, context } = SearchkitSchema({
  config: searchkitConfig,
  typeName: 'ResultSet',
  hitTypeName: 'ResultHit',
  addToQueryType: true
})

const server = new ApolloServer({
  typeDefs: [
    gql`
    type Query {
      root: String
    }

    type HitFields {
      title: String
    }

    type ResultHit implements SKHit {
      id: ID!
      fields: HitFields
      highlight: String
    }
  `, ...typeDefs
  ],
  resolvers: withSearchkitResolvers({
    ResultHit: {
      highlight: (hit: any) => JSON.stringify(hit.highlight)
    }
  }),
  introspection: true,
  playground: true,
  context: {
    ...context
  }
})