How to check for a value OR NULL on custom enddate field using yii syntax when calling entries?

Question

I have a section of 'deals/coupons' with custom startDate and endDate. These are needed so the client can load up a bunch of deals but only have them render to the page when a particular deal is 'active'.

The below syntax works to not show any deal before it's startdate has passed:

{% paginate craft.entries({
   section : 'dealDirectory',
   limit   : pageSize,
   startDate : '<=' ~ now
}) as pageInfo, dealEntries %}

And using the below code I can prevent deals from showing after their enddate but only if enddate has data:

{% paginate craft.entries({
   section : 'dealDirectory',
   limit   : pageSize,
   startDate : '<=' ~ now
   endDate : '>=' ~ now
}) as pageInfo, dealEntries %}

If enddate does not have a value it eliminates those entries from showing. I need to find a way to check if enddate is greater than now OR is null so that it will continue to show deals that do not have an enddate. Such as:

{% paginate craft.entries({
   section : 'dealDirectory',
   limit   : pageSize,
   startDate : '<=' ~ now
   endDate   : '>= ' ~ now ~ 'or is null'  // but this syntax incorrect
}) as pageInfo, dealEntries %}

I'm having a hard time finding a reference for this type of markup.

Answer 1

Shooting in the dark here, but looking off this ticket and the ECM parameter value syntax in the docs, could you do something like:

{% paginate craft.entries({
    section : 'dealDirectory',
    limit   : pageSize,
    startDate : '<=' ~ now
    endDate: 'or', '>= ' ~ now, 'not null'
}) as pageInfo, dealEntries %}

The or is a total guess based on the and in the other ticket.