On my site I have products. Each product has many releases. Each release has many changelogs. A changelog is one of many categories (eg, "Bug Fix", "Performance Improvement" etc).
I have created useful auto generated pages for each product, which lists all the changelogs for a product of a category (Eg "Product's Bug Fix History").
However, due to how data is structured and cached it's impossible to know if there are any "Bug Fixes" for a product without doing very expensive queries.
On the history pages themselves, I put a meta noindex tag on the page if no changelogs exist. However, I'm unsure if I should include these pages on my sitemap.
Would it be better to include them on my sitemap when possibly at a lot of them are meta-noindexed, or just allow for natural crawler discovery?