[LUCENE-7081] Docvalues terms dict should sometimes prefix-compress fixed-length data.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 6.0
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Robert Muir
• Created: 08/Mar/16 15:43
• Updated: 28/Aug/22 14:51
• Resolved: 10/Mar/16 13:02

Description

For Sorted/SortedSet types, we encode ordinals and a term dictionary (similar to old lucene 3 term dictionary).

Originally we had no prefix compression, so we "save space" in the fixed-width case by avoiding addressing, we can just use multiplication: https://github.com/apache/lucene-solr/blob/master/lucene/core/src/java/org/apache/lucene/codecs/lucene54/Lucene54DocValuesConsumer.java#L423-L425

But it means no compression whatsoever of the actual bytes, even if values are enormous, I don't think its necessarily a good tradeoff. The lack of prefix compression can become much more magnified now that we have fixed width 128-bit point types in the sandbox...