By default posts imported with WP All Import do not get indexed by Relevanssi. The importing process does not trigger Relevanssi indexing. That is, however, easy to remedy:
add_action( 'pmxi_saved_post', 'post_saved', 10, 1 );
function post_saved( $id ) {
relevanssi_index_doc( $id, true, relevanssi_get_custom_fields(), true );
}Add this code to your site, and any posts imported with WP All Import will be indexed with Relevanssi. Do note that this will make the importing process run slower.
If you reindex your site will that take care of any imported post?
Yes. Once the posts are in the database, they’re like any other post. It’s just that when they come in through the import, they don’t pass through Relevanssi.