Here's a very recent thread on the matter: http://lucene.472066.n3.nabble.com/facet-method-enum-vs-fc-td1681277.html
> Thanks Yonik. I hadn't actually been using "enum" on facets with a > small number of unique values; the wiki page doesn't give much guidance > on when each is called for. Do you have any rule of thumb for how few > unique values is "few enough" to want to use method=enum? Does it > matter if the field is single or multi-valued? > > Can you in general explain a bit more about the facet methods? The wiki > leaves me a bit confused. (I will happily turn anything you say into > additional language on the wiki, if the wiki lets me edit it, including > any answer to above). > > So first, the wiki suggests: "The default value is fc (except for > BoolField) since it tends to use less memory and is faster when a field > has many unique terms in the index. " > > Is this actualy true? If facet.method is left unspecified, > facet.method=enum will be used on any BoolField, and facet.method=fc > will be used on any other type of field? > > Both methods can work on multi-valued fields in 1.4, right? > > Then it's a bit extra confusing becuase while facet.method=enum always > works the same way, it seems like facet.method=fc chooses different > algorithms under the hood (depending on single vs multi-valued field, > possibly also depending on number of unique terms?), which you can't > actually specify, you just need to let the fc stuff choose on it's own. > That's not mentioned in the wiki, but I think I've seen it mentioned > before, and trying to look at the source gives me this impression too. > Is this correct? > > Thanks for any additional guidance, this stuff continues to confuse me > despite trying to read what I can on it. > > Jonathan > > Yonik Seeley wrote: > > On Thu, Oct 14, 2010 at 3:42 PM, Jonathan Rochkind <rochk...@jhu.edu> wrote: > >> I believe that should work fine in Solr 1.4.1. Creating a field with > >> just first letter of author is definitely the right (possibly only) way > >> to allow facetting on first letter of author's name. > >> > >> I have very voluminous facets (few facet values, many docs in each > >> value) like that in my app too, works fine. > >> > >> I get confused over the different facetting methods available in 1.4.1, > >> and exactly when each is called for. If you see initial problems, you > >> could try switching the facet.method and see what happens. > > > > Right - for faceting on first letter, you should probably use > > facet.method=enum since there will only be 26 values (assuming > > english/western languages). > > > > In the future, I'm hoping we can come up with a smarter way to pick > > the facet.method if it's not supplied. The new flex API in 4.0-dev > > should help out here. > > > > -Yonik > > http://www.lucidimagination.com
