Shawn Heisey [s...@elyograg.org] wrote: >On 4/9/2014 11:53 PM, Toke Eskildsen wrote: >> The memory allocation for enum is both low and independent of the amount >> of unique values in the facets. The trade-off is that is is very slow >> for medium- to high-cardinality fields.
> This is where it is extremely beneficial to have enough RAM to cache > your entire index. The term list must be enumerated for every facet > request, but if the data is already in the OS disk cache, this is very > fast. Very fast compared to not cached, yes, but still slow compared to fc, for high-cardinality. The processing overhead per term is a great deal larger for enum. I recently ran some tests with Solr's different faceting methods for 50M+ values, but stopped measuring for enum as it took so much longer than the other methods. For a fully cached index. > If facets are happening on lots of fields and are heavily utilized, > facet.method=enum should be used, and there must be plenty of RAM to > cache all or most of the index data on the machine. I do not understand how the number of facets has any influence on the choice between enum and fc. As Solr (sadly) does not support combined structures for multiple facets, each facet is independent from the others. Shouldn't the choice be done for each individual facet? - Toke Eskildsen
