[LUCENE-9850] Explore PFOR for Doc ID delta encoding (instead of FOR)

• Type: Task
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 9.0
• Fix Version/s: 9.0
• Component/s: core/codecs
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Greg Miller
• Created: 17/Mar/21 22:23
• Updated: 28/Aug/22 16:18
• Resolved: 14/Apr/21 12:42

Description

It'd be interesting to explore using PFOR instead of FOR for doc ID encoding. Right now PFOR is used for positions, frequencies and payloads, but FOR is used for doc ID deltas. From a recent conversation on the dev mailing list, it sounds like this decision was made based on the optimization possible when expanding the deltas.

I'd be interesting in measuring the index size reduction possible with switching to PFOR compared to the performance reduction we might see by no longer being able to apply the deltas in as optimal a way.

Issue Links

• links to: GitHub Pull Request #69