You don’t need to index the field for function queries, see: https://lucene.apache.org/solr/guide/8_6/docvalues.html.
Function queries, as opposed to sorting, faceting and grouping are evaluated at search time where the search process is already parked on the document anyway, so answering the question “for doc X, what is the value of field Y” to compute the score. DocValues are still more efficient I think, although I haven’t measured explicitly... For sorting, faceting and grouping, it’s a much different story. Take sorting. You have to ask “for field Y, what’s the value in docX and docZ?”. Say you’re parked on docX. Doc Z is long gone and getting the value for field Y much more expensive. Also, docValues will not increase memory requirements _unless used_. Otherwise they’ll just sit there on disk. They will certainly increase disk space whether used or not. And _not_ using docValues when you facet, group or sort will also _certainly_ increase your heap requirements since the docValues structure must be built on the heap rather than be in MMapDirectory space. Best, Erick > On Nov 4, 2020, at 5:32 AM, uyilmaz <uyil...@vivaldi.net.INVALID> wrote: > > Hi, > > I'm by no means expert on this so if anyone sees a mistake please correct me. > > I think you need to index this field, since boost functions are added to the > query as optional clauses > (https://lucene.apache.org/solr/guide/6_6/the-dismax-query-parser.html#TheDisMaxQueryParser-Thebf_BoostFunctions_Parameter). > It's like boosting a regular field by putting ^2 next to it in a query. > Storing or enabling docValues will unnecesarily consume space/memory. > > On Tue, 3 Nov 2020 16:10:50 -0800 > Wei <weiwan...@gmail.com> wrote: > >> Hi, >> >> I have a couple of primitive single value numeric type fields, their >> values are used in boosting functions, but not used in sort/facet. or in >> returned response. Should I use docValues for them in the schema? I can >> think of the following options: >> >> 1) indexed=true, stored=true, docValues=false >> 2) indexed=true, stored=false, docValues=true >> 3) indexed=false, stored=false, docValues=true >> >> What would be the performance implications for these options? >> >> Best, >> Wei > > > -- > uyilmaz <uyil...@vivaldi.net>
