Hi all, I'm sending this email as there seem to be different expectations about the future of FieldCache depending on who you are asking. To me FieldCache (and uninverting in general) is a legacy feature that has been superseded by doc values since version 4.0, when we introduced them. But we seem to still care a lot about uninverting, which does not make sense to me since everybody should have moved to doc values already?
For the record, doc values have many benefits over FieldCache like better compression (table compression, gcd compression, prefix compression of the terms dicts, etc.), faster reopens, the fact that data is stored off-heap and in master they also have better support for sparse fields, which is something that FieldCache cannot do due to the fact that it is built in random doc ID order (or it would have to generate more garbage and slow down reopens even more). The documentation ( https://cwiki.apache.org/confluence/display/solr/DocValues) and some online resources (eg. https://support.lucidworks.com/hc/en-us/articles/201839163-When-to-use-DocValues-in-Solr) are already recommending to use doc values for sorting, faceting and function queries. I think it's time to schedule the entire removal of FieldCache from Solr?
