dgraph-io/badger · error

ErrBannedKey

ErrBannedKey

Error message

Key is using the banned prefix

What it means

ErrBannedKey is returned when a read/write key belongs to a banned namespace. When WithNamespaceOffset is configured, the uint64 namespace extracted at that offset is checked against db.bannedNamespaces (db.go:1945) and banned namespaces are rejected on both reads and writes.

Source

Thrown at errors.go:47

	// ErrConflict is returned when a transaction conflicts with another transaction. This can
	// happen if the read rows had been updated concurrently by another transaction.
	ErrConflict = stderrors.New("Transaction Conflict. Please retry")

	// ErrReadOnlyTxn is returned if an update function is called on a read-only transaction.
	ErrReadOnlyTxn = stderrors.New("No sets or deletes are allowed in a read-only transaction")

	// ErrDiscardedTxn is returned if a previously discarded transaction is reused.
	ErrDiscardedTxn = stderrors.New("This transaction has been discarded. Create a new one")

	// ErrEmptyKey is returned if an empty key is passed on an update function.
	ErrEmptyKey = stderrors.New("Key cannot be empty")

	// ErrInvalidKey is returned if the key has a special !badger! prefix,
	// reserved for internal usage.
	ErrInvalidKey = stderrors.New("Key is using a reserved !badger! prefix")

	// ErrBannedKey is returned if the read/write key belongs to any banned namespace.
	ErrBannedKey = stderrors.New("Key is using the banned prefix")

	// ErrThresholdZero is returned if threshold is set to zero, and value log GC is called.
	// In such a case, GC can't be run.
	ErrThresholdZero = stderrors.New(
		"Value log GC can't run because threshold is set to zero")

	// ErrNoRewrite is returned if a call for value log GC doesn't result in a log file rewrite.
	ErrNoRewrite = stderrors.New(
		"Value log GC attempt didn't result in any cleanup")

	// ErrRejected is returned if a value log GC is called either while another GC is running, or
	// after DB::Close has been called.
	ErrRejected = stderrors.New("Value log GC request rejected")

	// ErrInvalidRequest is returned if the user request is invalid.
	ErrInvalidRequest = stderrors.New("Invalid request")

	// ErrManagedTxn is returned if the user tries to use an API which isn't

View on GitHub (pinned to 2a001d466f)

Solutions

1. Stop issuing keys for banned namespaces in the application layer
2. Remove the namespace from the banned list with SetBannedNamespaces if the ban was unintended
3. Ensure keys are at least NamespaceOffset+8 bytes long so the namespace is read correctly

Example fix

// before
key := makeTenantKey(tenantID, k) // tenantID may be banned
rerr := txn.Get(key)               // ErrBannedKey
// after
if banned[tenantID] {
    return fmt.Errorf("tenant %d is banned", tenantID)
}
rerr := txn.Get(makeTenantKey(tenantID, k))

if len(key) < db.opt.NamespaceOffset+8 {
    return errors.New("key too short to carry namespace")
}
ns := binary.BigEndian.Uint64(key[db.opt.NamespaceOffset:])
if banned.Has(ns) {
    return fmt.Errorf("namespace %d is banned", ns)
}

if _, err := txn.Get(key); err != nil {
    if errors.Is(err, badger.ErrBannedKey) {
        return ErrTenantBlocked
    }
    return err
}

When it happens

Trigger: Any Set/Get/Delete whose key, at opt.NamespaceOffset, encodes a namespace previously registered via db.SetBannedNamespaces; keys shorter than NamespaceOffset+8 may also misbehave in that check.

Common situations: Multi-tenant setups banning a tenant's namespace (e.g. after abuse or data deletion) while old application code still sends that tenant's keys.

Related errors

• ErrValueLogSize
• ErrEmptyKey
• ErrInvalidKey
• ErrInvalidRequest
• ErrZeroBandwidth

AI-assisted analysis of dgraph-io/badger@2a001d466f (2026-09-05). Data as JSON: /api/errors/27822da52984e993. Report an issue: GitHub.