prevent duplicate results in discovery search (#3459)

discovery/store.go

@@ -229,10 +229,14 @@ func (s *sqlStore) get(serviceID string, startAfter int) (map[string]vc.Verifiab
 // Wildcard matching is supported by prefixing or suffixing the value with an asterisk (*).
 // It returns the presentations which contain credentials that match the given query.
 func (s *sqlStore) search(serviceID string, query map[string]string) ([]vc.VerifiablePresentation, error) {
+	// first only select columns also used in group by clause
+	// if the query is empty, there's no need to do a join
 	stmt := s.db.Model(&presentationRecord{}).
-		Where("service_id = ?", serviceID).
-		Joins("inner join discovery_credential ON discovery_credential.presentation_id = discovery_presentation.id")
-	stmt = store.CredentialStore{}.BuildSearchStatement(stmt, "discovery_credential.credential_id", query)
+		Where("service_id = ?", serviceID)
+	if len(query) > 0 {
+		stmt = stmt.Joins("inner join discovery_credential ON discovery_credential.presentation_id = discovery_presentation.id")
+		stmt = store.CredentialStore{}.BuildSearchStatement(stmt, "discovery_credential.credential_id", query)
+	}
 
 	var matches []presentationRecord
 	if err := stmt.Preload("Credentials").Preload("Credentials.Credential").Find(&matches).Error; err != nil {

discovery/store_test.go

@@ -196,6 +196,18 @@ func Test_sqlStore_search(t *testing.T) {
 		require.Len(t, actualVPs, 1)
 		assert.Equal(t, vpAlice.ID.String(), actualVPs[0].ID.String())
 	})
+	t.Run("find all", func(t *testing.T) {
+		vps := []vc.VerifiablePresentation{vpAlice, vpBob}
+		c := setupStore(t, storageEngine.GetSQLDatabase())
+		for _, vp := range vps {
+			err := c.add(testServiceID, vp, 0)
+			require.NoError(t, err)
+		}
+
+		actualVPs, err := c.search(testServiceID, map[string]string{})
+		require.NoError(t, err)
+		require.Len(t, actualVPs, 2)
+	})
 	t.Run("not found", func(t *testing.T) {
 		vps := []vc.VerifiablePresentation{vpAlice, vpBob}
 		c := setupStore(t, storageEngine.GetSQLDatabase())