[LUCENE-10156] BlendedInfixSuggester incorrectly scores items with high and low weights

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 8.10
• Component/s: core/search
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Aleksandr Popitich
• Created: 06/Oct/21 21:55
• Updated: 28/Aug/22 16:27

Description

After fix LUCENE-8343 BlendedInfixSuggester applies additional 1 / LINEAR_COEF coefficient for the weight that falls to (-10, 10) range. Where LINEAR_COEF = 0.1

Link to the changes: Code

Whilst it fixes zero score issues, it causes incorrect scoring between item with weight < 10 and item with weight > 10.

Example:

Blender - POSITION_RECIPROCAL (weight / (1 + position))

Item	Weight	Score
AAA	8	8 * (1 / 0.1) * (1 / (1 + 0)) =  80
AAB	11	11 * (1 / (1 + 0)) = 11

So item AAA with lower weight bubbled up, but in fact, AAA must be on the bottom.

Issue Links

• is caused by: LUCENE-8343 BlendedInfixSuggester bad score calculus for certain suggestion weights