Fix age sort direction and revert broad getSort null change

- Revert IS NULL addition in getSort (caused unintended side effects)
- Add targeted birthdate case in getPerformerSort that flips direction
  (birthdate is inverse to age: lower date = older, so ASC exchanges
  with DESC) and adds IS NULL for nulls-last behavior

Author: slick-daddy

pkg/sqlite/performer.go

@@ -872,6 +872,17 @@ func (qb *PerformerStore) getPerformerSort(findFilter *models.FindFilterType) (s
 		sortQuery += qb.sortByLastOAt(direction)
 	case "latest_scene":
 		sortQuery += qb.sortByLatestScene(direction)
+	case "birthdate":
+		// birthdate is inversely related to age (older = lower date).
+		// flip direction so DESC means "oldest first".
+		colName := getColumn(performerTable, "birthdate")
+		dir := getSortDirection(direction)
+		if dir == "ASC" {
+			dir = "DESC"
+		} else {
+			dir = "ASC"
+		}
+		sortQuery += " ORDER BY " + colName + " IS NULL, " + colName + " " + dir
 	default:
 		sortQuery += getSort(sort, direction, "performers")
 	}

pkg/sqlite/sql.go

@@ -99,7 +99,7 @@ func getSort(sort string, direction string, tableName string) string {
 		return " ORDER BY COUNT(distinct " + colName + ") " + direction
 	case strings.Compare(sort, "filesize") == 0:
 		colName := getColumn(tableName, "size")
-		return " ORDER BY " + colName + " IS NULL, " + colName + " " + direction
+		return " ORDER BY " + colName + " " + direction
 	case strings.HasPrefix(sort, randomSeedPrefix):
 		// seed as a parameter from the UI
 		seedStr := sort[len(randomSeedPrefix):]
@@ -117,13 +117,13 @@ func getSort(sort string, direction string, tableName string) string {
 			colName = sort
 		}
 		if strings.Compare(sort, "name") == 0 {
-			return " ORDER BY " + colName + " IS NULL, " + colName + " COLLATE NATURAL_CI " + direction
+			return " ORDER BY " + colName + " COLLATE NATURAL_CI " + direction
 		}
 		if strings.Compare(sort, "title") == 0 {
-			return " ORDER BY " + colName + " IS NULL, " + colName + " COLLATE NATURAL_CI " + direction
+			return " ORDER BY " + colName + " COLLATE NATURAL_CI " + direction
 		}
 
-		return " ORDER BY " + colName + " IS NULL, " + colName + " " + direction
+		return " ORDER BY " + colName + " " + direction
 	}
 }