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// Copyright 2014 The Cockroach Authors.
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.
package batcheval
import (
// ErrTransactionUnsupported is returned when a non-transactional command is
// evaluated in the context of a transaction.
var ErrTransactionUnsupported = errors.New("not supported within a transaction")
// VerifyTransaction runs sanity checks verifying that the transaction in the
// header and the request are compatible.
func VerifyTransaction(
h roachpb.Header, args roachpb.Request, permittedStatuses ...roachpb.TransactionStatus,
) error {
if h.Txn == nil {
return errors.Errorf("no transaction specified to %s", args.Method())
if !bytes.Equal(args.Header().Key, h.Txn.Key) {
return errors.Errorf("request key %s should match txn key %s", args.Header().Key, h.Txn.Key)
statusPermitted := false
for _, s := range permittedStatuses {
if h.Txn.Status == s {
statusPermitted = true
if !statusPermitted {
return roachpb.NewTransactionStatusError(
fmt.Sprintf("cannot perform %s with txn status %v", args.Method(), h.Txn.Status),
return nil
// WriteAbortSpanOnResolve returns true if the abort span must be written when
// the transaction with the given status is resolved.
func WriteAbortSpanOnResolve(status roachpb.TransactionStatus) bool {
return status == roachpb.ABORTED
// SetAbortSpan clears any AbortSpan entry if poison is false.
// Otherwise, if poison is true, creates an entry for this transaction
// in the AbortSpan to prevent future reads or writes from
// spuriously succeeding on this range.
func SetAbortSpan(
ctx context.Context,
rec EvalContext,
batch engine.ReadWriter,
ms *enginepb.MVCCStats,
txn enginepb.TxnMeta,
poison bool,
) error {
// Read the current state of the AbortSpan so we can detect when
// no changes are needed. This can help us avoid unnecessary Raft
// proposals.
var curEntry roachpb.AbortSpanEntry
exists, err := rec.AbortSpan().Get(ctx, batch, txn.ID, &curEntry)
if err != nil {
return err
if !poison {
if !exists {
return nil
return rec.AbortSpan().Del(ctx, batch, ms, txn.ID)
entry := roachpb.AbortSpanEntry{
Key: txn.Key,
Timestamp: txn.Timestamp,
Priority: txn.Priority,
if exists && curEntry.Equal(entry) {
return nil
// curEntry already escapes, so assign entry to curEntry and pass
// that to Put instead of allowing entry to escape as well.
curEntry = entry
return rec.AbortSpan().Put(ctx, batch, ms, txn.ID, &curEntry)
// CanPushWithPriority returns true if the given pusher can push the pushee
// based on its priority.
func CanPushWithPriority(pusher, pushee *roachpb.Transaction) bool {
return (pusher.Priority > enginepb.MinTxnPriority && pushee.Priority == enginepb.MinTxnPriority) ||
(pusher.Priority == enginepb.MaxTxnPriority && pushee.Priority < pusher.Priority)
// CanCreateTxnRecord determines whether a transaction record can be created for
// the provided transaction. If not, the function will return an error. If so,
// the function may modify the provided transaction.
func CanCreateTxnRecord(rec EvalContext, txn *roachpb.Transaction) error {
// Provide the transaction's minimum timestamp. The transaction could not
// have written a transaction record previously with a timestamp below this.
// We use InclusiveTimeBounds to remain backward compatible. However, if we
// don't need to worry about compatibility, we require the transaction to
// have a minimum timestamp field.
// TODO(nvanbenschoten): Replace this with txn.MinTimestamp in v20.1.
txnMinTS, _ := txn.InclusiveTimeBounds()
if util.RaceEnabled {
newTxnMinTS := txn.MinTimestamp
if newTxnMinTS.IsEmpty() {
return errors.Errorf("no minimum transaction timestamp provided: %v", txn)
} else if newTxnMinTS != txnMinTS {
return errors.Errorf("minimum transaction timestamp differs from lower time bound: %v", txn)
ok, minCommitTS, reason := rec.CanCreateTxnRecord(txn.ID, txn.Key, txnMinTS)
if !ok {
return roachpb.NewTransactionAbortedError(reason)
return nil
// SynthesizeTxnFromMeta creates a synthetic transaction object from the
// provided transaction metadata. The synthetic transaction is not meant to be
// persisted, but can serve as a representation of the transaction for outside
// observation. The function also checks whether it is possible for the
// transaction to ever create a transaction record in the future. If not, the
// returned transaction will be marked as ABORTED and it is safe to assume that
// the transaction record will never be written in the future.
func SynthesizeTxnFromMeta(rec EvalContext, txn enginepb.TxnMeta) roachpb.Transaction {
// Construct the transaction object.
synthTxnRecord := roachpb.TransactionRecord{
TxnMeta: txn,
Status: roachpb.PENDING,
// Set the LastHeartbeat timestamp to the intent's timestamp.
// We use this as an indication of client activity.
LastHeartbeat: txn.Timestamp,
// Determine whether the transaction record could ever actually be written
// in the future.
txnMinTS := txn.MinTimestamp
if txnMinTS.IsEmpty() {
// If the transaction metadata's min timestamp is empty then provide its
// provisional commit timestamp to CanCreateTxnRecord. If this timestamp
// is larger than the transaction's real minimum timestamp then
// CanCreateTxnRecord may return false positives (i.e. it determines
// that the record could eventually be created when it actually
// couldn't) but will never return false negatives (i.e. it will never
// determine that the record could not be created when it actually
// could). This is important, because it means that we may end up
// failing to push a finalized transaction but will never determine that
// a transaction is finalized when it still could end up committing.
// TODO(nvanbenschoten): This case is only possible for intents that
// were written by a transaction coordinator before v19.2, which means
// that we can remove it in v20.1 and replace it with:
// synthTxnRecord.Status = roachpb.ABORTED
txnMinTS = txn.Timestamp
// If we don't need to worry about compatibility, disallow this case.
if util.RaceEnabled {
log.Fatalf(context.TODO(), "no minimum transaction timestamp provided: %v", txn)
ok, minCommitTS, _ := rec.CanCreateTxnRecord(txn.ID, txn.Key, txnMinTS)
if ok {
// Forward the provisional commit timestamp by the minimum timestamp that
// the transaction would be able to create a transaction record at.
} else {
// Mark the transaction as ABORTED because it is uncommittable.
synthTxnRecord.Status = roachpb.ABORTED
return synthTxnRecord.AsTransaction()
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