UIF (UnInvertedField which are the entries in the FieldValueCache) was
completely removed from use at some point in the 5.x timeframe.
It was part of the JSON Facet API though, and so later SOLR-8466 added
back support to regular faceting by calling JSON Faceting when
> I'm new to solr, and I'm using solr 6.6.
> I did some testing with solr 4.9 and 6.6 on the same index with the same
> faceting queries on the multivalued fields.
> In first run (with empty cache) solr 6.6 performs much better, but when I
> run same queries couple more times solr 4.9 is a little bit faster than solr
> FieldValueCache is empty in solr 6.6, and solr 4.9 uses this cache with a
> good hit ratio (0.9).
> I have specified this cache inside solrconfig.xml for both solr 6.6 and 4.9.
> I have also tried same thing by reindexing documents with docValues set to
> false for the faceting fields and run queries again and FieldValueCache is
> still empty.
> Is it possible to use FieldValueCache in solr 6.6?
> Thanks in advance.
> Sent from: http://lucene.472066.n3.nabble.com/Solr-User-f472068.html
> Hi Yonik,
> Thanks for your answer :).
> It works.
> Another question:
> What is recommended to be used in solr 6.6 for faceting (docValues or
> UnInvertedField), because UnInvertedField performs better for subsequent
> I assume that docValues is more beneficial in terms of heap memory use, but
> should I use fieldValueCache instead if hit ratio is good?
docValues is a safer default. UIF needs to rebuild every time the
index is changed (and is also one reason why it's faster once it is
If one uses real docValues (at index time), then there will even be
less heap memory.
A note to those trying out UIF: method=uif is an execution hint only
and will be ignored if you've indexed docValues. We should probably
add some way of forcing it at some point.