[SOLR-6168] enhance collapse QParser so that "group head" documents can be selected by more complex sort options

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.7.1, 4.8.1
• Fix Version/s: 5.4, 6.0
• Assignee: Chris M. Hostetter
• Reporter: Umesh Prasad
• Created: 14/Jun/14 07:03
• Updated: 09/May/16 18:55
• Resolved: 15/Nov/15 22:40

Description

The fundemental goal of this issue is add additional support to the CollapseQParser so that as an alternative to the existing min/max localparam options, more robust sort syntax can be used to sort on multiple criteria when selecting the "group head" documents used to represent each collapsed group.

Since support for arbitrary, multi-clause, sorting is almost certainly going to require more RAM then the existing min/max functionaly, this new functionality should be in addition to the existing min/max localparam implementation, not a replacement of it.

(NOTE: early comments made in this jira may be confusing in historical context due to the way this issue was originally filed as a bug report)

Issue Links

• is blocked by: LUCENE-6808 Term(Ord)ValComparator.value return BytesRefs that are re-used internally
• is blocked by: SOLR-8082 can't query against negative float or double values when indexed="false" docValues="true" multiValued="false"
• relates to: SOLR-8295 collapse parser can trigger NPE when a segment has empty DocValues for collapse field (ie: no doc in segment has a value)