[LUCENE-3079] Faceting module

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.4, 4.0-ALPHA
• Component/s: modules/facet
• Lucene Fields: New, Patch Available
• Assignee: Shai Erera
• Reporter: Michael McCandless
• Created: 07/May/11 11:01
• Updated: 28/Aug/22 12:46
• Resolved: 30/Jun/11 09:07

Description

Faceting is a hugely important feature, available in Solr today but
not [easily] usable by Lucene-only apps.

We should fix this, by creating a shared faceting module.

Ideally, we factor out Solr's faceting impl, and maybe poach/merge
from other impls (eg Bobo browse).

Hoss describes some important challenges we'll face in doing this
(http://markmail.org/message/5w35c2fr4zkiwsz6), copied here:

To look at "faceting" as a concrete example, there are big the reasons 
faceting works so well in Solr: Solr has total control over the 
index, knows exactly when the index has changed to rebuild caches, has a 
strict schema so it can make sense of field types and 
pick faceting algos accordingly, has multi-phase distributed search 
approach to get exact counts efficiently across multiple shards, etc...
(and there are still a lot of additional enhancements and improvements 
that can be made to take even more advantage of knowledge solr has because 
it "owns" the index that we no one has had time to tackle)

This is a great list of the things we face in refactoring. It's also
important because, if Solr needed to be so deeply intertwined with
caching, schema, etc., other apps that want to facet will have the
same "needs" and so we really have to address them in creating the
shared module.

I think we should get a basic faceting module started, but should not
cut Solr over at first. We should iterate on the module, fold in
improvements, etc., and then, once we can fully verify that cutting
over doesn't hurt Solr (ie lose functionality or performance) we can
later cutover.

Issue Links

• blocks: LUCENE-3097 Post grouping faceting