I’m doing some fairly simple facet queries in a two-shard 5.3 SolrCloud index on fields like this:
<field name="city" type="string" indexed="true" stored="false" docValues="true”/> that look something like this: q=...&fl=id,score&facet.field=city&facet=true&f.city.facet.mincount=1&f.cit y.facet.limit=50&rows=0&start=0&facet.method=fc (no, NOT facet.method=enum - the usage of the filterCache there is pretty well documented) Watching the filterCache stats, it appears that every one of these queries causes the "inserts" counter to be incremented by one. Distinct "q=" queries also increase the "size", and eviction happens as normal. If I repeat the same query a few times, "lookups" is not incremented, so these entries generally appear to be completely wasted. (Although when running a lot of these queries, it appears as though a very small set also increment the "lookups" counter, but only a small set, and I haven’t figured out why some are special.) So the question is, why does this facet query have anything to do with the filterCache? This causes a huge amount of filterCache churn with no apparent benefit.
