canopy-network/canopy · error · ErrStoreGet

reverse iterator not supported on subtree store

Error message

reverse iterator not supported on subtree store

What it means

Raised unconditionally by subtreeStore.ReIterator for the same reason as Iterator: the subtree store is a pending-writes overlay with no reverse (descending-key) scan capability. Reverse iteration is intentionally unsupported rather than silently incorrect.

Source

Thrown at store/txn.go:370

	s.l.Lock()
	s.ops[lib.MemHash(key)] = valueOp{key: key, value: value, version: s.version, op: opSet}
	s.l.Unlock()
	return nil
}

func (s *subtreeStore) Delete(key []byte) lib.ErrorI {
	s.l.Lock()
	s.ops[lib.MemHash(key)] = valueOp{key: key, version: s.version, op: opDelete}
	s.l.Unlock()
	return nil
}

func (s *subtreeStore) Iterator([]byte) (lib.IteratorI, lib.ErrorI) {
	return nil, ErrStoreGet(fmt.Errorf("iterator not supported on subtree store"))
}

func (s *subtreeStore) RevIterator([]byte) (lib.IteratorI, lib.ErrorI) {
	return nil, ErrStoreGet(fmt.Errorf("reverse iterator not supported on subtree store"))
}

// Copy creates a new Txn with the same configuration and txn as the original
func (t *Txn) Copy(reader TxnReaderI, writer TxnWriterI) *Txn {
	return &Txn{
		reader:       reader,
		writer:       writer,
		prefix:       t.prefix,
		state:        t.state,
		sort:         t.sort,
		writeVersion: t.writeVersion,
		txn:          t.txn.copy(),
	}
}

// txn() returns a copy of the current transaction txn
func (t *txn) copy() *txn {
	t.l.Lock()

View on GitHub (pinned to ee8197d91d)

Solutions

1. Perform reverse iteration on the underlying versioned store instead of the subtree overlay.
2. Collect written keys in a list and sort descending if reverse traversal of pending ops is required.
3. Restrict subtreeStore usage to Get/Set/Delete point operations.

When it happens

Trigger: Thrown at store/txn.go:370 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of canopy-network/canopy@ee8197d91d (2026-09-06). Data as JSON: /api/errors/899aa25898821ae4. Report an issue: GitHub.