Relevanssi automatically indexes new posts; no settings are required.
Are the unindexed posts new posts that have been added on the site, or old posts that have become unindexed? You can check by adding a new post and then checking it with the Relevanssi debugger (Settings > Relevanssi > Debugging). Is the post indexed?
How are new posts added to your site? New posts as usual, or some other method, like a front-end form?
Thank you for the quick reply!
I spent a lot of time checking and it seems that new posts (including CPT) are being indexed. These are often added through the front end.
But still there’s a lot of posts (usually several hundred) which are not indexed and which I have to do manually every so often. Is there a way to see a list of posts which are not indexed?
Nothing ready-made – when Relevanssi needs to know, it gets it from the database tables (“show posts that are in wp_posts, but not in wp_relevanssi”).
It would be best if you could figure out what is deindexing the posts; fixing that would be the best solution for this problem.
If that’s not possible, then I would recommend running the indexing on a schedule. Here are instructions for that. Since you’re looking to add the missing posts, all you need is the second part, relevanssi_build_index(true, false, 100);. If you can get that running automatically a couple of times per day, you should be fine.