canonicalFilter property
The default filter that is applied when a user performs a search without checking any filters on the search page.
The filter applied to every search request when quality improvement such as query expansion is needed. In the case a query does not have a sufficient amount of results this filter will be used to determine whether or not to enable the query expansion flow. The original filter will still be used for the query expanded search. This field is strongly recommended to achieve high search quality. For more information about filter syntax, see SearchRequest.filter.
Implementation
core.String? canonicalFilter;