For any kind of product search I'd go for an external index (I'm strongly biased towards ES, but SOLR is certainly on par feature-wise). Postgres is my go-to relational database and I do love it's json/hstore features, but it does not offer features such as stemming, aggregation, proper weighting or any other analyzer based features.

Adding ES as a secondary datastore just for search is relatively easy in terms of technical complexity, especially if you already have json data. The more complex part is deciding on a relevancy model, but you'd have to do that for every technology you choose.