moreLikeThis (preview) in Azure AI Search

moreLikeThis=[key] is a query parameter in the Search Documents API that finds documents similar to the document specified by the document key. When a search request is made with moreLikeThis, a query is generated with search terms extracted from the given document that describe that document best. The generated query is then used to make the search request. The moreLikeThis parameter can't be used with the search parameter, search=[string].

By default, the contents of all top-level searchable fields are considered. If you want to specify particular fields instead, you can use the searchFields parameter.

The moreLikeThis parameter isn't supported for complex types and the presence of complex types will impact your query logic. If your index is a complex type, you must set searchFields to the top-level searchable fields over which moreLikeThis iterates. For example, if the index has a searchable field1 of type Edm.String, and field2 that's a complex type with searchable subfields, the value of searchFields must be set to field1 to exclude field2.

Examples

All following examples use the hotels sample from Quickstart: Create a search index in the Azure portal.

Simple query

The following query finds documents whose description fields are most similar to the field of the source document as specified by the moreLikeThis parameter:

GET /indexes/hotels-sample-index/docs?moreLikeThis=29&searchFields=Description&api-version=2024-05-01-preview

In this example, the request searches for hotels similar to the one with HotelId 29. Rather than using HTTP GET, you can also invoke MoreLikeThis using HTTP POST:

POST /indexes/hotels-sample-index/docs/search?api-version=2024-05-01-preview
    {
      "moreLikeThis": "29",
      "searchFields": "Description"
    }

Apply filters

MoreLikeThis can be combined with other common query parameters like $filter. For instance, the query can be restricted to only hotels whose category is 'Budget' and where the rating is higher than 3.5:

GET /indexes/hotels-sample-index/docs?moreLikeThis=20&searchFields=Description&$filter=(Category eq 'Budget' and Rating gt 3.5)&api-version=2024-05-01-preview

Select fields and limit results

The $top selector can be used to limit how many results should be returned in a MoreLikeThis query. Also, fields can be selected with $select. Here the top three hotels are selected along with their ID, Name, and Rating:

GET /indexes/hotels-sample-index/docs?moreLikeThis=20&searchFields=Description&$filter=(Category eq 'Budget' and Rating gt 3.5)&$top=3&$select=HotelId,HotelName,Rating&api-version=2024-05-01-preview

Next steps

You can use any REST client for this exercise.