Here is some detail about how grouping is implemented in Solr. http://fulmicoton.com/posts/grouping-in-solr/
On Mon, Aug 5, 2013 at 2:42 AM, Tony Paloma <to...@valvesoftware.com> wrote: > Thanks Paul. That's helpful. I'm not familiar with the concept of custom > caches. Would this be custom Java code or something defined in the > config/schema? Can you point me to some documentation? > > Another workaround I was thinking of using was making two Solr queries > when wanting to sort groups by price desc. One to get the number of total > groups and then another that gets groups sorted by price asc starting from > ngroups - (start+rows) and then just flip the ordering to fake sorting by > min(price) desc, but I was worried about the performance implications of > that. > > SOLR-2072 has a similar request. > https://issues.apache.org/jira/browse/SOLR-2072 > > Bryan's comment is exactly what I'm looking for: > > I would like to able to use sort and group.sort together such that the > group.sort is applied with in the group first and the first document of > each group is then used as the representative document to perform the > overall sorting of groups. > > The latest comment there suggests that it's a bug in distributed mode, but > I don't think that's the case since I'm only using one instance of Solr > with no sharding or anything. > > -----Original Message----- > From: Paul Masurel [mailto:paul.masu...@gmail.com] > Sent: Sunday, August 04, 2013 2:54 PM > To: solr-user@lucene.apache.org > Subject: Re: Unexpected behavior when sorting groups > > Dear Tony, > > The behavior you described is correct, and what you are requiring is > impossible with Solr as it is. > > I wouldn't however say it is a limitation of Solr : your problem is > actually difficult and require some preprocessing. > > One solution if it is feasible for you is to precompute the lowest price > of your groups beforehands and add a field to all of the document of your > group. > > The other way to address your problem is to do that within Solr. > This can be done by adding a custom cache holding these values. > You can implement the computation of the min price in the warm method. > > You can then add a custom function to return the result stored in this > cache. Function values can be used for sorting. > > If if does not exist yet, you may open a ticket. I will try and get > authorization to opensource a solution for this. > > Regards, > > Paul > > > > > On Sat, Aug 3, 2013 at 12:00 AM, Tony Paloma <to...@valvesoftware.com > >wrote: > > > I'm using field collapsing to group documents by a single field and > > have run into something unexpected with how sorting of the groups > > works. Right now I have each group return one document. The documents > > within each group are sorted by a field ("price") in ascending order > > using group.sort so that the document returned for each group in the > > search results is the cheapest document of the group. If I sort the > > groups amongst themselves using sort=price asc, I get what I expect > > with groups having documents whose lowest price value is low show > > first and groups having documents whose lowest price value is high show > last. > > > > If I change this to sort on price desc, what happens is not what I > > would expect. I would like the groups to be returned in reverse order > > from what happened when sorting by price asc. Instead, what happens is > > the groups are sorted in descending order according to the highest > > priced document in each group. I want groups to be sorted in > > descending order according to the lowest priced document in each group, > but it appears this is not possible. > > In other words, it appears sorting when groups are involved is limited > > to either MAX([field]) DESC or MIN([field]) ASC. The other two > > combinations are not possible. Does anyone know whether or not this is > > in fact impossible, and if not, how I might put in a feature request? > > > > > > -- > ______________________________________________ > > Masurel Paul > e-mail: paul.masu...@gmail.com > -- ______________________________________________ Masurel Paul e-mail: paul.masu...@gmail.com
