Add Artist (discography) size, and show sizes in Download caption

db/migration/20201012210022_add_artist_playlist_size.go

@@ -0,0 +1,41 @@
+package migration
+
+import (
+	"database/sql"
+
+	"github.com/pressly/goose"
+)
+
+func init() {
+	goose.AddMigration(Up20201012210022, Down20201012210022)
+}
+
+func Up20201012210022(tx *sql.Tx) error {
+	_, err := tx.Exec(`
+alter table artist
+	add size integer default 0 not null;
+create index if not exists artist_size
+	on artist(size);
+
+alter table playlist
+	add size integer default 0 not null;
+create index if not exists playlist_size
+	on playlist(size);
+
+update playlist set size = ifnull((
+    select sum(size)
+    from media_file f
+             left join playlist_tracks pt on f.id = pt.media_file_id
+    where pt.playlist_id = playlist.id
+), 0);`)
+
+	if err != nil {
+		return err
+	}
+	notice(tx, "A full rescan will be performed to calculate artists (discographies) and playlists sizes.")
+	return forceFullRescan(tx)
+}
+
+func Down20201012210022(tx *sql.Tx) error {
+	return nil
+}