[LUCENE-9099] Correctly handle repeats in ordered and unordered intervals

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 8.5
• Lucene Fields: New
• Assignee: Alan Woodward
• Reporter: Alan Woodward
• Created: 18/Dec/19 10:21
• Updated: 28/Aug/22 15:54
• Resolved: 06/Feb/20 14:59

Description

If you have repeating intervals in an ordered or unordered interval source, you currently get somewhat confusing behaviour:

• ORDERED(a, a, b) will return an extra interval over just `a b` if it first matches `a a b`, meaning that you can get incorrect results if used in a CONTAINING filter - CONTAINING(ORDERED(x, y), ORDERED(a, a, b)) will match on the document `a x a b y`
• UNORDERED(a, a) will match on documents that just containg a single `a`.

It is possible to deal with the unordered case when building sources by rewriting duplicates to nested ORDERED clauses, so that UNORDERED(a, b, c, a, b) becomes UNORDERED(ORDERED(a, a), ORDERED(b, b), c), but this then breaks MAXGAPS filtering.

We should try and fix this within intervals themselves.

Issue Links

• links to: GitHub Pull Request #1097