[LUCENE-4586] Change default ResultMode of FacetRequest to PER_NODE_IN_TREE

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 4.1, 6.0
• Component/s: modules/facet
• Lucene Fields: New, Patch Available
• Assignee: Shai Erera
• Reporter: Shai Erera
• Created: 04/Dec/12 08:30
• Updated: 28/Aug/22 13:33
• Resolved: 05/Dec/12 11:32

Description

Today the default ResultMode is GLOBAL_FLAT, but it should be PER_NODE_IN_TREE. ResultMode is being used whenever you set the depth of FacetRequest to greater than 1. The difference between the two is:

• PER_NODE_IN_TREE would then compute the top-K categories recursively, for every top category at every level (up to depth). The results are returned in a tree structure as well. For instance:

Date
  2010
    March
    February
  2011
    April
    May

• GLOBAL_FLAT computes the top categories among all the nodes up to depth, and returns a flat list of categories.

GLOBAL_FLAT is faster to compute than PER_NODE_IN_TREE (it just computes top-K among N total categories), however I think that it's less intuitive, and therefore should not be used as a default. In fact, I think this is kind of an expert usage.