Merge #4666

4666: Add a score threshold search parameter r=ManyTheFish a=dureuill

# Pull Request

## Related issue
Fixes https://github.com/meilisearch/meilisearch/issues/4609

## What does this PR do?
- See [usage](https://meilisearch.notion.site/Filter-by-score-usage-224a183ce7b24ca99b6a9a8da755668a?pvs=25#95b76ded400342ba9ab3d67c734836f0) and [the known limitation](https://meilisearch.notion.site/Filter-by-score-usage-224a183ce7b24ca99b6a9a8da755668a?pvs=25#e4e32195bf0e4195b5daecdbb7a97a17)


Co-authored-by: Louis Dureuil <louis@meilisearch.com>

milli/src/search/new/bucket_sort.rs

@@ -28,6 +28,7 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
     scoring_strategy: ScoringStrategy,
     logger: &mut dyn SearchLogger<Q>,
     time_budget: TimeBudget,
+    ranking_score_threshold: Option<f64>,
 ) -> Result<BucketSortOutput> {
     logger.initial_query(query);
     logger.ranking_rules(&ranking_rules);
@@ -164,7 +165,19 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
             loop {
                 let bucket = std::mem::take(&mut ranking_rule_universes[cur_ranking_rule_index]);
                 ranking_rule_scores.push(ScoreDetails::Skipped);
+
+                // remove candidates from the universe without adding them to result if their score is below the threshold
+                if let Some(ranking_score_threshold) = ranking_score_threshold {
+                    let current_score = ScoreDetails::global_score(ranking_rule_scores.iter());
+                    if current_score < ranking_score_threshold {
+                        all_candidates -= bucket | &ranking_rule_universes[cur_ranking_rule_index];
+                        back!();
+                        continue;
+                    }
+                }
+
                 maybe_add_to_results!(bucket);
+
                 ranking_rule_scores.pop();
 
                 if cur_ranking_rule_index == 0 {
@@ -220,6 +233,18 @@ pub fn bucket_sort<'ctx, Q: RankingRuleQueryTrait>(
         debug_assert!(
             ranking_rule_universes[cur_ranking_rule_index].is_superset(&next_bucket.candidates)
         );
+
+        // remove candidates from the universe without adding them to result if their score is below the threshold
+        if let Some(ranking_score_threshold) = ranking_score_threshold {
+            let current_score = ScoreDetails::global_score(ranking_rule_scores.iter());
+            if current_score < ranking_score_threshold {
+                all_candidates -=
+                    next_bucket.candidates | &ranking_rule_universes[cur_ranking_rule_index];
+                back!();
+                continue;
+            }
+        }
+
         ranking_rule_universes[cur_ranking_rule_index] -= &next_bucket.candidates;
 
         if cur_ranking_rule_index == ranking_rules_len - 1

milli/src/search/new/matches/mod.rs

@@ -523,6 +523,7 @@ mod tests {
                 &mut crate::DefaultSearchLogger,
                 &mut crate::DefaultSearchLogger,
                 TimeBudget::max(),
+                None,
             )
             .unwrap();
 

milli/src/search/new/mod.rs

@@ -573,6 +573,7 @@ pub fn execute_vector_search(
     embedder_name: &str,
     embedder: &Embedder,
     time_budget: TimeBudget,
+    ranking_score_threshold: Option<f64>,
 ) -> Result<PartialSearchResult> {
     check_sort_criteria(ctx, sort_criteria.as_ref())?;
 
@@ -602,6 +603,7 @@ pub fn execute_vector_search(
         scoring_strategy,
         placeholder_search_logger,
         time_budget,
+        ranking_score_threshold,
     )?;
 
     Ok(PartialSearchResult {
@@ -631,6 +633,7 @@ pub fn execute_search(
     placeholder_search_logger: &mut dyn SearchLogger<PlaceholderQuery>,
     query_graph_logger: &mut dyn SearchLogger<QueryGraph>,
     time_budget: TimeBudget,
+    ranking_score_threshold: Option<f64>,
 ) -> Result<PartialSearchResult> {
     check_sort_criteria(ctx, sort_criteria.as_ref())?;
 
@@ -719,6 +722,7 @@ pub fn execute_search(
             scoring_strategy,
             query_graph_logger,
             time_budget,
+            ranking_score_threshold,
         )?
     } else {
         let ranking_rules =
@@ -733,6 +737,7 @@ pub fn execute_search(
             scoring_strategy,
             placeholder_search_logger,
             time_budget,
+            ranking_score_threshold,
         )?
     };