Method Init

core/metadata/db.go:156–236

Init ensures the database is at the correct version and performs any needed migrations.

(ctx context.Context)

// Init ensures the database is at the correct version
// and performs any needed migrations.
func (m *DB) Init(ctx context.Context) error {
	// errSkip is used when no migration or version needs to be written
	// to the database and the transaction can be immediately rolled
	// back rather than performing a much slower and unnecessary commit.
	var errSkip = errors.New("skip update")

	err := m.db.Update(func(tx *bolt.Tx) error {
		var (
			// current schema and version
			schema  = "v0"
			version = 0
		)

		// i represents the index of the first migration
		// which must be run to get the database up to date.
		// The migration's version will be checked in reverse
		// order, decrementing i for each migration which
		// represents a version newer than the current
		// database version
		i := len(migrations)

		for ; i > 0; i-- {
			migration := migrations[i-1]

			bkt := tx.Bucket([]byte(migration.schema))
			if bkt == nil {
				// Hasn't encountered another schema, go to next migration
				if schema == "v0" {
					continue
				}
				break
			}
			if schema == "v0" {
				schema = migration.schema
				vb := bkt.Get(bucketKeyDBVersion)
				if vb != nil {
					v, _ := binary.Varint(vb)
					version = int(v)
				}
			}

			if version >= migration.version {
				break
			}
		}

		// Previous version of database found
		if schema != "v0" {
			updates := migrations[i:]

			// No migration updates, return immediately
			if len(updates) == 0 {
				return errSkip
			}

			for _, m := range updates {
				t0 := time.Now()
				if err := m.migrate(tx); err != nil {