txn: skips resolving lock in auto commit optimistic statement (pingcap#58676)

close pingcap#58675

Author: ekexium

pkg/kv/option.go

@@ -116,6 +116,8 @@ const (
 	SessionID
 	// BackgroundGoroutineLifecycleHooks is the hooks to track the start and end of background goroutine
 	BackgroundGoroutineLifecycleHooks
+	// PrewriteEncounterLockPolicy is the policy to handle lock conflict during prewrite
+	PrewriteEncounterLockPolicy
 )
 
 // TxnSizeLimits is the argument type for `SizeLimits` option

pkg/session/txn.go

@@ -665,23 +665,23 @@ type txnFuture struct {
 }
 
 func (tf *txnFuture) wait() (kv.Transaction, error) {
+	options := []tikv.TxnOption{tikv.WithTxnScope(tf.txnScope)}
 	startTS, err := tf.future.Wait()
 	failpoint.Inject("txnFutureWait", func() {})
 	if err == nil {
-		if tf.pipelined {
-			return tf.store.Begin(tikv.WithTxnScope(tf.txnScope), tikv.WithStartTS(startTS), tikv.WithDefaultPipelinedTxn())
+		options = append(options, tikv.WithStartTS(startTS))
+	} else {
+		if config.GetGlobalConfig().Store == config.StoreTypeUniStore {
+			return nil, err
 		}
-		return tf.store.Begin(tikv.WithTxnScope(tf.txnScope), tikv.WithStartTS(startTS))
-	} else if config.GetGlobalConfig().Store == config.StoreTypeUniStore {
-		return nil, err
+		logutil.BgLogger().Warn("wait tso failed", zap.Error(err))
 	}
 
-	logutil.BgLogger().Warn("wait tso failed", zap.Error(err))
-	// It would retry get timestamp.
 	if tf.pipelined {
-		return tf.store.Begin(tikv.WithTxnScope(tf.txnScope), tikv.WithDefaultPipelinedTxn())
+		options = append(options, tikv.WithDefaultPipelinedTxn())
 	}
-	return tf.store.Begin(tikv.WithTxnScope(tf.txnScope))
+
+	return tf.store.Begin(options...)
 }
 
 // HasDirtyContent checks whether there's dirty update on the given table.

pkg/sessiontxn/isolation/base.go

@@ -614,6 +614,21 @@ func (p *baseTxnContextProvider) SetOptionsBeforeCommit(
 	if commitTSChecker != nil {
 		txn.SetOption(kv.CommitTSUpperBoundCheck, commitTSChecker)
 	}
+
+	// Optimization:
+	// If an auto-commit optimistic transaction can retry in pessimistic mode,
+	// do not resolve locks when prewrite.
+	// 1. safety: The locks can be resolved later when it retries in pessimistic mode.
+	// 2. benefit: In high-contention scenarios, pessimistic transactions perform better.
+	prewriteEncounterLockPolicy := transaction.TryResolvePolicy
+	if sessVars.TxnCtx.CouldRetry &&
+		sessVars.IsAutocommit() &&
+		!sessVars.InTxn() &&
+		!sessVars.TxnCtx.IsPessimistic {
+		prewriteEncounterLockPolicy = transaction.NoResolvePolicy
+	}
+	txn.SetOption(kv.PrewriteEncounterLockPolicy, prewriteEncounterLockPolicy)
+
 	return nil
 }
 

pkg/sessiontxn/isolation/optimistic.go

@@ -46,21 +46,32 @@ func (p *OptimisticTxnContextProvider) ResetForNewTxn(sctx sessionctx.Context, c
 	p.getStmtForUpdateTSFunc = p.getTxnStartTS
 }
 
-func (p *OptimisticTxnContextProvider) onTxnActive(_ kv.Transaction, tp sessiontxn.EnterNewTxnType) {
+func (p *OptimisticTxnContextProvider) onTxnActive(
+	txn kv.Transaction,
+	tp sessiontxn.EnterNewTxnType,
+) {
 	sessVars := p.sctx.GetSessionVars()
-	sessVars.TxnCtx.CouldRetry = isOptimisticTxnRetryable(sessVars, tp)
+	sessVars.TxnCtx.CouldRetry = isOptimisticTxnRetryable(sessVars, tp, txn.IsPipelined())
 }
 
 // isOptimisticTxnRetryable (if returns true) means the transaction could retry.
 // We only consider retry in this optimistic mode.
 // If the session is already in transaction, enable retry or internal SQL could retry.
 // If not, the transaction could always retry, because it should be auto committed transaction.
 // Anyway the retry limit is 0, the transaction could not retry.
-func isOptimisticTxnRetryable(sessVars *variable.SessionVars, tp sessiontxn.EnterNewTxnType) bool {
+func isOptimisticTxnRetryable(
+	sessVars *variable.SessionVars,
+	tp sessiontxn.EnterNewTxnType,
+	isPipelined bool,
+) bool {
 	if tp == sessiontxn.EnterNewTxnDefault {
 		return false
 	}
 
+	if isPipelined {
+		return false
+	}
+
 	// If retry limit is 0, the transaction could not retry.
 	if sessVars.RetryLimit == 0 {
 		return false

pkg/store/driver/txn/txn_driver.go

@@ -311,6 +311,8 @@ func (txn *tikvTxn) SetOption(opt int, val any) {
 		txn.KVTxn.SetSessionID(val.(uint64))
 	case kv.BackgroundGoroutineLifecycleHooks:
 		txn.KVTxn.SetBackgroundGoroutineLifecycleHooks(val.(transaction.LifecycleHooks))
+	case kv.PrewriteEncounterLockPolicy:
+		txn.KVTxn.SetPrewriteEncounterLockPolicy(val.(transaction.PrewriteEncounterLockPolicy))
 	}
 }