Merge #4108

4108: Fix bug where search with distinct attribute and no ranking, returns offset+limit hits r=curquiza a=vivek-26

# Pull Request

## Related issue
Fixes #4078 

## What does this PR do?
This PR - 
- Fixes bug where search with distinct attribute and no ranking, returns offset+limit hits.
- Adds unit and integration tests.

## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!


Co-authored-by: Vivek Kumar <vivek.26@outlook.com>

milli/src/search/new/bucket_sort.rs

@@ -46,18 +46,27 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
         if let Some(distinct_fid) = distinct_fid {
             let mut excluded = RoaringBitmap::new();
             let mut results = vec![];
+            let mut skip = 0;
             for docid in universe.iter() {
-                if results.len() >= from + length {
+                if results.len() >= length {
                     break;
                 }
                 if excluded.contains(docid) {
                     continue;
                 }
+
                 distinct_single_docid(ctx.index, ctx.txn, distinct_fid, docid, &mut excluded)?;
+                skip += 1;
+                if skip <= from {
+                    continue;
+                }
+
                 results.push(docid);
             }
+
             let mut all_candidates = universe - excluded;
             all_candidates.extend(results.iter().copied());
+
             return Ok(BucketSortOutput {
                 scores: vec![Default::default(); results.len()],
                 docids: results,