Merge #565

565: Feat accept the frequency value for the matchingStrategy search r=curquiza a=Ja7ad

# Pull Request

## Related issue
Fixes #540

## What does this PR do?
- This PR accept the frequency value for the matchingStrategy search

## 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: Javad <ja7ad@live.com>

.code-samples.meilisearch.yaml

@@ -470,12 +470,17 @@ search_parameter_guide_show_ranking_score_details_1: |-
   })
 search_parameter_guide_matching_strategy_1: |-
   resp, err := client.Index("movies").Search("big fat liar", &meilisearch.SearchRequest{
-    MatchingStrategy:    "last",
+    MatchingStrategy:    Last,
   })
 search_parameter_guide_matching_strategy_2: |-
   resp, err := client.Index("movies").Search("big fat liar", &meilisearch.SearchRequest{
-    MatchingStrategy:    "all",
+    MatchingStrategy:    All,
   })
+search_parameter_guide_matching_strategy_3: |-
+  client.Index("movies").Search("white shirt", &meilisearch.SearchRequest{
+    MatchingStrategy: Frequency,
+  })
+
 search_parameter_guide_hitsperpage_1: |-
   client.Index("movies").Search("", &meilisearch.SearchRequest{
     HitsPerPage: 15,

index_search_test.go

@@ -236,7 +236,7 @@ func TestIndex_Search(t *testing.T) {
 						"book_id": float64(123), "title": "Pride and Prejudice",
 					},
 				},
-				EstimatedTotalHits: 20,
+				EstimatedTotalHits: 21,
 				Offset:             0,
 				Limit:              1,
 			},
@@ -553,6 +553,28 @@ func TestIndex_Search(t *testing.T) {
 			},
 			wantErr: false,
 		},
+		{
+			name: "TestIndexSearchWithMatchStrategyFrequency",
+			args: args{
+				UID:    "indexUID",
+				client: sv,
+				query:  "white shirt",
+				request: &SearchRequest{
+					MatchingStrategy: Frequency,
+				},
+			},
+			want: &SearchResponse{
+				Hits: []interface{}{
+					map[string]interface{}{
+						"book_id": float64(1039), "title": "The Girl in the white shirt",
+					},
+				},
+				EstimatedTotalHits: 1,
+				Offset:             0,
+				Limit:              20,
+			},
+			wantErr: false,
+		},
 		{
 			name: "TestIndexSearchWithInvalidIndex",
 			args: args{
@@ -1296,7 +1318,7 @@ func TestIndex_SearchWithSort(t *testing.T) {
 						"book_id": float64(7), "title": "Don Quixote",
 					},
 				},
-				EstimatedTotalHits: 20,
+				EstimatedTotalHits: 21,
 				Offset:             0,
 				Limit:              4,
 			},

main_test.go

@@ -234,6 +234,7 @@ func setUpIndexForFaceting(client ServiceManager) {
 		{BookID: 254, Title: "Lolita", Tag: "Novel", Year: 1955},
 		{BookID: 921, Title: "The Brothers Karamazov", Tag: "Novel", Year: 1879},
 		{BookID: 1032, Title: "Crime and Punishment", Tag: "Crime fiction", Year: 1866},
+		{BookID: 1039, Title: "The Girl in the white shirt", Tag: "white shirt", Year: 1999},
 	}
 	task, err := idx.AddDocuments(booksTest)
 	if err != nil {

types.go

@@ -123,6 +123,22 @@ type (
 	SortFacetType          string // SortFacetType is type of facet sorting, alpha or count
 	TaskStatus             string // TaskStatus is the status of a task.
 	ProximityPrecisionType string // ProximityPrecisionType accepts one of the ByWord or ByAttribute
+	MatchingStrategy       string // MatchingStrategy one of the Last, All, Frequency
+)
+
+const (
+	// Last returns documents containing all the query terms first. If there are not enough results containing all
+	// query terms to meet the requested limit, Meilisearch will remove one query term at a time,
+	// starting from the end of the query.
+	Last MatchingStrategy = "last"
+	// All only returns documents that contain all query terms. Meilisearch will not match any more documents even
+	// if there aren't enough to meet the requested limit.
+	All MatchingStrategy = "all"
+	// Frequency returns documents containing all the query terms first. If there are not enough results containing
+	//all query terms to meet the requested limit, Meilisearch will remove one query term at a time, starting
+	//with the word that is the most frequent in the dataset. frequency effectively gives more weight to terms
+	//that appear less frequently in a set of results.
+	Frequency MatchingStrategy = "frequency"
 )
 
 const (
@@ -372,7 +388,7 @@ type SearchRequest struct {
 	AttributesToHighlight   []string             `json:"attributesToHighlight,omitempty"`
 	HighlightPreTag         string               `json:"highlightPreTag,omitempty"`
 	HighlightPostTag        string               `json:"highlightPostTag,omitempty"`
-	MatchingStrategy        string               `json:"matchingStrategy,omitempty"`
+	MatchingStrategy        MatchingStrategy     `json:"matchingStrategy,omitempty"`
 	Filter                  interface{}          `json:"filter,omitempty"`
 	ShowMatchesPosition     bool                 `json:"showMatchesPosition,omitempty"`
 	ShowRankingScore        bool                 `json:"showRankingScore,omitempty"`