apply_filters( 'relevanssi_default_tax_query_relation', string $relation = 'AND' )
Filters the default tax_query relation.
Parameters
$relation
(string) The default relation, default “AND”.
More information
When Relevanssi processes the tax_query part from the search query, the tax_query relation parameter is fetched from the query. If there’s no relation defined in the query, Relevanssi will use a default value, which is “AND”. If you prefer it to be “OR”, you can set that with this filter hook:
add_filter( 'relevanssi_default_tax_query_relation', function() { return 'OR'; } );