CrowdingSpec

Specification for crowding. Crowding improves the diversity of search results by limiting the number of results that share the same field value. For example, crowding on the color field with a maxCount of 3 and mode DROP_CROWDED_RESULTS will return at most 3 results with the same color across all pages.

JSON representation 
{
  "field": string,
  "maxCount": integer,
  "mode": enum (Mode)
}
Fields
field

string

The field to use for crowding. Documents can be crowded by a field in the Document object. Crowding field is case sensitive.
maxCount

integer

The maximum number of documents to keep per value of the field. Once there are at least maxCount previous results which contain the same value for the given field (according to the order specified in orderBy), later results with the same value are "crowded away". If not specified, the default value is 1.
mode

enum (Mode)

Mode to use for documents that are crowded away.

Mode

Enum describing the mode to use for documents that are crowded away. They can be dropped or demoted to the later pages.

Enums
MODE_UNSPECIFIED Unspecified crowding mode. In this case, server behavior defaults to Mode.DROP_CROWDED_RESULTS.
DROP_CROWDED_RESULTS Drop crowded results.
DEMOTE_CROWDED_RESULTS_TO_END Demote crowded results to the later pages.