| 1 | package draftstate |
| 2 | |
| 3 | import ( |
| 4 | "database/sql" |
| 5 | "fmt" |
| 6 | "os" |
| 7 | "path/filepath" |
| 8 | ) |
| 9 | |
| 10 | // VACUUM INTO reads a consistent SQLite snapshot including committed WAL |
| 11 | // frames. Copying only the main database would lose acknowledged input. |
| 12 | func backupBeforeUpgrade(db *sql.DB, path string, version int) error { |
| 13 | backup := fmt.Sprintf("%s.pre-v%d.sqlite", path, SchemaVersion) |
| 14 | if _, err := os.Stat(backup); err == nil { |
| 15 | return nil |
| 16 | } else if !os.IsNotExist(err) { |
| 17 | return err |
| 18 | } |
| 19 | file, err := os.CreateTemp(filepath.Dir(path), ".draft-upgrade-*.sqlite") |
| 20 | if err != nil { |
| 21 | return err |
| 22 | } |
| 23 | temporary := file.Name() |
| 24 | if err := file.Close(); err != nil { |
| 25 | return err |
| 26 | } |
| 27 | defer os.Remove(temporary) |
| 28 | if _, err := db.Exec(`VACUUM INTO ?`, temporary); err != nil { |
| 29 | return fmt.Errorf("backup draft schema %d: %w", version, err) |
| 30 | } |
| 31 | if err := os.Chmod(temporary, 0600); err != nil { |
| 32 | return err |
| 33 | } |
| 34 | // Link publishes without replacing a snapshot another upgrader produced. |
| 35 | if err := os.Link(temporary, backup); err != nil && !os.IsExist(err) { |
| 36 | return err |
| 37 | } |
| 38 | return nil |
| 39 | } |
| 40 |