Add a new field to indicate whether to perform a length comparison

json.go

@@ -457,6 +457,10 @@ type JSONArrayExpression struct {
 	column      string
 	keys        []string
 	equalsValue interface{}
+	// Add a new field to indicate whether to perform a length comparison
+	length bool
+	// Add a new field to store the expected length value
+	lengthValue int
 }
 
 // Contains checks if column[keys] contains the value given. The keys parameter is only supported for MySQL and SQLite.
@@ -475,6 +479,13 @@ func (json *JSONArrayExpression) In(value interface{}, keys ...string) *JSONArra
 	return json
 }
 
+// Length checks if the length of the JSON array matches the given value.
+func (json *JSONArrayExpression) Length(value int) *JSONArrayExpression {
+	json.length = true
+	json.lengthValue = value
+	return json
+}
+
 // Build implements clause.Expression
 func (json *JSONArrayExpression) Build(builder clause.Builder) {
 	if stmt, ok := builder.(*gorm.Statement); ok {
@@ -504,6 +515,10 @@ func (json *JSONArrayExpression) Build(builder clause.Builder) {
 					builder.WriteByte(')')
 				}
 				builder.WriteByte(')')
+				// Add new logic to handle length comparison
+			case json.length:
+				builder.WriteString("JSON_LENGTH(" + stmt.Quote(json.column) + ") = ")
+				builder.AddVar(stmt, json.lengthValue)
 			}
 		case "sqlite":
 			switch {
@@ -551,13 +566,19 @@ func (json *JSONArrayExpression) Build(builder clause.Builder) {
 				builder.WriteString(" IN ")
 				builder.AddVar(stmt, json.equalsValue)
 				builder.WriteString(" END")
+			case json.length:
+				builder.WriteString("json_array_length(" + stmt.Quote(json.column) + ") = ")
+				builder.AddVar(stmt, json.lengthValue)
 			}
 		case "postgres":
 			switch {
 			case json.contains:
 				builder.WriteString(stmt.Quote(json.column))
 				builder.WriteString(" ? ")
 				builder.AddVar(stmt, json.equalsValue)
+			case json.length:
+				builder.WriteString("array_length(" + stmt.Quote(json.column) + "::jsonb::text[], 1) = ")
+				builder.AddVar(stmt, json.lengthValue)
 			}
 		}
 	}

json_test.go

@@ -523,5 +523,20 @@ func TestJSONArrayQuery(t *testing.T) {
 			t.Fatalf("failed to find params with json value and keys, got error %v", err)
 		}
 		AssertEqual(t, len(retMultiple), 1)
+
+		// 新增的长度测试用例
+		var retLength []Param
+		if err := DB.Where(datatypes.JSONArrayQuery("config").Length(2)).Find(&retLength).Error; err != nil {
+			t.Fatalf("failed to find params with json array length, got error %v", err)
+		}
+		AssertEqual(t, len(retLength), 1)
+		AssertEqual(t, retLength[0].DisplayName, cmp1.DisplayName)
+
+		// 测试嵌套数组的长度
+		if err := DB.Where(datatypes.JSONArrayQuery("config").Length(2).Contains("a", "test")).Find(&retLength).Error; err != nil {
+			t.Fatalf("failed to find params with json array length and contains, got error %v", err)
+		}
+		AssertEqual(t, len(retLength), 1)
+		AssertEqual(t, retLength[0].DisplayName, cmp3.DisplayName)
 	}
 }