I think Evergreen is pushing the limits of search within PostgreSQL; I've been working with Solr as an additional interface.
Solr does so much of the features we want in Evergreen search and it's much simpler to extend/improve/customise than what is shown in Example: Adding a Local Subjects (690) search index
The current Solr search solution is an add-on to Evergreen but can be integrated on top of the same Apache - a demo is visible at http://demo.ils.edoceo.com/sap/sunshine
This has to be done from an external script, I've got a stub of one going in PHP working with the Solr JSON interface. Indexes about 32k records in 5 minutes.
This Work in Progress is available at https://github.com/edoceo/sap