Your use case is somewhat special in that it involves 10 fields. With that many nested facets the JSON facet API may or may not outperform streaming rollups. For most other cases JSON facet API will outperform rollups.
Joel Bernstein http://joelsolr.blogspot.com/ On Wed, Oct 17, 2018 at 11:21 PM RAUNAK AGRAWAL <agrawal.rau...@gmail.com> wrote: > Thanks a lot Joel. This makes sense but in my use case, I am aggregating 10 > fields but it is performing 2x better than the facet streaming. > > On Wed, Oct 17, 2018 at 6:56 PM Joel Bernstein <joels...@gmail.com> wrote: > > > They are very different. > > > > The "facet" expression sends a request to the JSON facet API which pushes > > the aggregation into the search engine. In most scenarios this is the > > preferred method because it only streams aggregated results. I would > always > > try the "facet" expression first before going to rollup. > > > > The "rollup" expression rolls up aggregations over a sorted stream of > > tuples. It almost always involves exporting and sorting entire result > sets > > with the /export handler. There are only two reasons to use this > approach: > > > > 1) Very high cardinality faceting. By very high I mean millions of facet > > values are being returned in the same query. > > 2) Rollups following any kind of relational algebra. For example a rollup > > on top of a hashJoin. > > > > > > Joel Bernstein > > http://joelsolr.blogspot.com/ > > > > > > On Tue, Oct 16, 2018 at 8:54 AM RAUNAK AGRAWAL <agrawal.rau...@gmail.com > > > > wrote: > > > > > Hi Guys, > > > > > > I am trying to do an aggregation (sum) using streaming API. I have > around > > > 10 billion documents in my collection and every document has around 10 > > > docValues. > > > > > > So streaming facet is taking close to 6 secs to respond with > aggregation > > on > > > 10 fields while streaming rollup is returning the response in 2 secs. > > > > > > So my questions are: > > > > > > 1. What is the fundamental difference between streaming facet and > rollUp. > > > 2. When to use facet and when to use rollUp. > > > > > > Thanks > > > > > >
