I'm interested in caching facet counts, keyed to query/DocSet domain (like filterCache, but caching facet counts instead of DocSets).
Trying not to open a duplicate issue, I found SOLR-1617 <https://issues.apache.org/jira/browse/SOLR-1617>, but I wasn't clear on whether it's applicable, or whether it's about maintaining per-segment UIF data structures (which could be considered a type of cache). I'd appreciate any guidance/suggestions on how to proceed -- revive SOLR-1617, or open a new issue; thanks! Michael ps- A version of the functionality I'm interested in is implemented and folded in to SOLR-13132 <https://issues.apache.org/jira/browse/SOLR-13132> (as a prerequisite for performance on that issue). But I think I may have buried the lead by including it there, since sort-by-relatedness is a relatively specialized use case, and a facet cache is more generally useful. The cache as implemented for SOLR-13132 is compatible across SimpleFacets and JSON facets, and is segment-aware (so should be NRT-friendly). It's particularly useful for high-cardinality fields and high-cardinality DocSet domains (e.g., facets on a main landing page).
