A cheap way to get information from page_props table for all links on page is needed. Two use cases are related to the DISPLAYTITLE: magic word (bug 17212) and to marking disambigs using the Disambiguator extension (bug 8339).
At a glance it seems like it would be possible to reuse LinkCache + LinkBatch for both purposes, adding one indexed query per batch per prop, which sounds fast enough to me. (We'd also need a hook in both to allow extensions to do this.)
The results could be stored in mGoodLinkFields in LinkCache, with names prefixed with "prop_" or something to distinguish them from the information from the page table that's in there right now. (This might require more hooks or not, depending on how we do them and how powerful we make them - if the hook for LinkCache allowed any queries, we'd need a separate one; if it just allowed stating prop names, it'd do here as well.)
This really seems implementable and sort of easy. Thoughts?
(CC-ing people involved in current patches to those two bugs and resident performance magicians.)