I've created a view listing a content type named foo, it has a custom field 'start_date' which can be left blank.
When a node's start_date field is left blank, it should always show in the listing. When it's populated, and the date is less than the current date - then the node should also be listed.
I've tried to use
hook_views_query_alter to do this, but it didn't do what I wanted as it's for changing the query itself.
Which hook should I use?