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 > > >
