Missing groups from GroupingSearch

[dongle-the-gadget]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

GroupingSearch might miss some groups, even if searching for docs using IndexSearcher.Search indicates that the group should be present.

For instance, using IndexSearcher.Search will reveal a document with field name and value CreateFileW, but using GroupingSearch, like below:

GroupingSearch groupingSearch = new("name");
groupingSearch.SetAllGroups(true);

// query here works with IndexSearcher.Search
var groups = groupingSearch.Search(searcher, query, 0, 10);

// groups variable doesn't contain all the possible groups.

contains no group with the name being CreateFileW.

In addition, the TotalGroupCount is inconsistent with that of the real dataset (in the repro below GroupingSearch returns 4 instead of the expected 10).

Expected Behavior

The group should exist in the search, and there should not be a mismatch between TotalGroupCount and the index.

Steps To Reproduce

A repro repository is here: https://github.com/dongle-the-gadget/TestLucene

The real dataset has documents of the following names:

CreateFile2
CreateFile2FromAppW
CreateFileA
CreateFileFromAppW
CreateFileMappingA
CreateFileMappingFromApp
CreateFileMappingW
CreateFileMoniker
CreateFileW
CreateFile2

Exceptions (if any)

No response

Lucene.NET Version

4.8.0-beta00016

.NET Version

8.0

Operating System

Windows 11

Anything else?

No response

[paulirwin]

I'll take investigating this one for the beta 18 release.