[LUCENE-10317] In PhraseQuery API, the explanation of getSlop is not inexact but could be more clear

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Not A Bug
• Affects Version/s: 5.2.1
• Component/s: core/search
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Claude Lepère
• Created: 15/Dec/21 18:17
• Updated: 28/Aug/22 16:32
• Resolved: 16/Dec/21 09:22

Description

The explanation says that searching for "quick fox" will match the document "the fox is quick" with a slop of 3.

That's true if the stop word "is" is not removed by the analyzer at indexing but, with the standard stop word list of Lucene which includes "is", a slop of 2 is enough.

As I understand the comment in the PhraseQuery source, switching the order of two words requires two moves (the first places the words atop one another) and the slop is 2, but, if "is" is not removed, a third "move" is needed to add "is" itself and the slop is 3. I am not sure of this explanation. I would be happy to have it confirmed ... or not.

I tested both cases in Lucene 5.2.1 but the text is the same in PhraseQuery API 8_0_0.