[LUCENE-5797] improve speed of norms merging

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.10
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Robert Muir
• Created: 30/Jun/14 18:33
• Updated: 28/Aug/22 14:11
• Resolved: 01/Jul/14 13:54

Description

Today we use the following procedure:

• track HashSet<Long> uniqueValues, until it exceeds 256 unique values.
• convert to array, sort and assign ordinals to each one
• create encoder map (HashMap<Long,Integer>) to encode each value.

This results in each value being hashed twice... but the vast majority of the time people will just be using single-byte norms and a simple array is enough for that range.