I’m having a similar issue. Our company uses a custom table for better searches on the back end. This table contains a list of WC product’s with custom columns. One of them is a product’s 4-digit date, such as 1889 or 1990. We’re trying to incorporate a date range search. We know it’s not possible for taxonomy range searches, so we’re attempting to modify the query args just like Kaz. I successfully query our custom table and add a list of post ids to $query_args['post__in'], but the posts are not included on the shop page!

For example, let’s say a user selects the dates 1913 to 1915. Normally we’ll get products exclusively with those dates; which happens to be only 9 products. I grab those dates from $customFieldsArray['_sft_pa_date']['active_terms']. I then run a query against our custom table and get another 5 products. The $query_args['post__in'] gets a total of 14 post ids in an array. Shop page only displays the original 9. I’ve been successful modifying the query to handle a custom meta query and setting post__not_in with a list of post ids that are successfully excluded.

Any thoughts?