updates the enum migration to perform a singular update for all values, using an SQL case statement

internal/db/bundb/migrations/util.go

@@ -35,6 +35,11 @@ import (
 	"github.com/uptrace/bun/schema"
 )
 
+// formatQuery formats given query + args according to given bun dialect, using for debug logging.
+func formatQuery(d schema.Dialect, query string, args ...any) string {
+	return schema.NewFormatter(d).FormatQuery(query, args...)
+}
+
 // convertEnums performs a transaction that converts
 // a table's column of our old-style enums (strings) to
 // more performant and space-saving integer types.
@@ -82,26 +87,31 @@ func convertEnums[OldType ~string, NewType ~int16](
 		return gtserror.Newf("error selecting total count: %w", err)
 	}
 
-	var updated int
+	var args []any
-	for old, new := range mapping {
+	var qbuf byteutil.Buffer
 
-		// Update old to new values.
+	// Prepare a singular UPDATE statement using
-		res, err := tx.NewUpdate().
+	// SET $newColumn = (CASE $column WHEN $old THEN $new ... END)
-			Table(table).
+	qbuf.WriteString("UPDATE ? SET ? = (CASE ? ")
-			Where("? = ?", bun.Ident(column), old).
+	args = append(args, bun.Ident(table))
-			Set("? = ?", bun.Ident(newColumn), new).
+	args = append(args, bun.Ident(newColumn))
-			Exec(ctx)
+	args = append(args, bun.Ident(column))
+	for old, new := range mapping {
+		qbuf.WriteString("WHEN ? THEN ? ")
+		args = append(args, old, new)
+	}
+	qbuf.WriteString("ELSE ? END)")
+	args = append(args, *defaultValue)
+
+	// Execute the prepared raw query with arguments.
+	res, err := tx.NewRaw(qbuf.String(), args...).Exec(ctx)
 	if err != nil {
 		return gtserror.Newf("error updating old column values: %w", err)
 	}
 
 	// Count number items updated.
-		n, _ := res.RowsAffected()
+	updated, _ := res.RowsAffected()
-		updated += int(n)
+	if total != int(updated) {
-	}
-
-	// Check total updated.
-	if total != updated {
 		log.Warnf(ctx, "total=%d does not match updated=%d", total, updated)
 	}