*: add a config to enable write statements to read on TiFlash

planner/core/integration_test.go

@@ -7130,3 +7130,54 @@ func TestCastTimeAsDurationToTiFlash(t *testing.T) {
  }
  tk.MustQuery("explain select cast(a as time), cast(b as time) from t;").CheckAt([]int{0, 2, 4}, rows)
 }
+
+func TestEnableTiFlashReadForWriteStmt(t *testing.T) {
+ store, dom := testkit.CreateMockStoreAndDomain(t)
+ tk := testkit.NewTestKit(t, store)
+
+ tk.MustExec("use test")
+ tk.MustExec("drop table if exists t")
+ tk.MustExec("create table t(a int, b int)")
+ tk.MustExec("insert into t values(1, 2)")
+ tk.MustExec("drop table if exists t2")
+ tk.MustExec("create table t2(a int)")
+ tk.MustExec("set @@tidb_allow_mpp=1; set @@tidb_enforce_mpp=1")
+ tk.MustExec("set @@tidb_isolation_read_engines = 'tiflash'")
+ tk.MustExec("set @@tidb_enable_tiflash_read_for_write_stmt = ON")
+
+ tbl, err := dom.InfoSchema().TableByName(model.CIStr{O: "test", L: "test"}, model.CIStr{O: "t", L: "t"})
+ require.NoError(t, err)
+ // Set the hacked TiFlash replica for explain tests.
+ tbl.Meta().TiFlashReplica = &model.TiFlashReplicaInfo{Count: 1, Available: true}
+
+ tbl2, err := dom.InfoSchema().TableByName(model.CIStr{O: "test", L: "test"}, model.CIStr{O: "t2", L: "t2"})
+ require.NoError(t, err)
+ // Set the hacked TiFlash replica for explain tests.
+ tbl2.Meta().TiFlashReplica = &model.TiFlashReplicaInfo{Count: 1, Available: true}
+
+ checkMpp := func(r [][]interface{}) {
+ check := false
+ for i := range r {
+ if r[i][2] == "mpp[tiflash]" {
+ check = true
+ break
+ }
+ }
+ require.Equal(t, check, true)
+ }
+
+ // Insert into ... select
+ rs := tk.MustQuery("explain insert into t2 select a+b from t").Rows()
+ checkMpp(rs)
+
+ rs = tk.MustQuery("explain insert into t2 select t.a from t2 join t on t2.a = t.a").Rows()
+ checkMpp(rs)
+
+ // Replace into ... select
+ rs = tk.MustQuery("explain replace into t2 select a+b from t").Rows()
+ checkMpp(rs)
+
+ // CTE
+ rs = tk.MustQuery("explain update t set a=a+1 where b in (select a from t2 where t.a > t2.a)").Rows()
+ checkMpp(rs)
+}

planner/optimize.go

@@ -88,9 +88,7 @@ func Optimize(ctx context.Context, sctx sessionctx.Context, node ast.Node, is in
  }
  }
 
- // Because for write stmt, TiFlash has a different results when lock the data in point get plan. We ban the TiFlash
- // engine in not read only stmt.
- if _, isolationReadContainTiFlash := sessVars.IsolationReadEngines[kv.TiFlash]; isolationReadContainTiFlash && !IsReadOnly(node, sessVars) {
+ if _, isolationReadContainTiFlash := sessVars.IsolationReadEngines[kv.TiFlash]; isolationReadContainTiFlash && !sessVars.EnableTiFlashReadForWriteStmt && !IsReadOnly(node, sessVars) {
  delete(sessVars.IsolationReadEngines, kv.TiFlash)
  defer func() {
  sessVars.IsolationReadEngines[kv.TiFlash] = struct{}{}

sessionctx/variable/session.go

@@ -1234,6 +1234,9 @@ type SessionVars struct {
  // ConstraintCheckInPlacePessimistic controls whether to skip the locking of some keys in pessimistic transactions.
  // Postpone the conflict check and constraint check to prewrite or later pessimistic locking requests.
  ConstraintCheckInPlacePessimistic bool
+
+ // EnableTiFlashReadForWriteStmt indicates whether to enable TiFlash to read for write statements.
+ EnableTiFlashReadForWriteStmt bool
 }
 
 // GetPreparedStmtByName returns the prepared statement specified by stmtName.
@@ -1432,94 +1435,95 @@ func NewSessionVars() *SessionVars {
  values: make(map[string]types.Datum),
  types: make(map[string]*types.FieldType),
  },
- systems: make(map[string]string),
- stmtVars: make(map[string]string),
- PreparedStmts: make(map[uint32]interface{}),
- PreparedStmtNameToID: make(map[string]uint32),
- PreparedParams: make([]types.Datum, 0, 10),
- TxnCtx: &TransactionContext{},
- RetryInfo: &RetryInfo{},
- ActiveRoles: make([]*auth.RoleIdentity, 0, 10),
- StrictSQLMode: true,
- AutoIncrementIncrement: DefAutoIncrementIncrement,
- AutoIncrementOffset: DefAutoIncrementOffset,
- Status: mysql.ServerStatusAutocommit,
- StmtCtx: new(stmtctx.StatementContext),
- AllowAggPushDown: false,
- AllowCartesianBCJ: DefOptCartesianBCJ,
- MPPOuterJoinFixedBuildSide: DefOptMPPOuterJoinFixedBuildSide,
- BroadcastJoinThresholdSize: DefBroadcastJoinThresholdSize,
- BroadcastJoinThresholdCount: DefBroadcastJoinThresholdSize,
- OptimizerSelectivityLevel: DefTiDBOptimizerSelectivityLevel,
- EnableOuterJoinReorder: DefTiDBEnableOuterJoinReorder,
- RetryLimit: DefTiDBRetryLimit,
- DisableTxnAutoRetry: DefTiDBDisableTxnAutoRetry,
- DDLReorgPriority: kv.PriorityLow,
- allowInSubqToJoinAndAgg: DefOptInSubqToJoinAndAgg,
- preferRangeScan: DefOptPreferRangeScan,
- EnableCorrelationAdjustment: DefOptEnableCorrelationAdjustment,
- LimitPushDownThreshold: DefOptLimitPushDownThreshold,
- CorrelationThreshold: DefOptCorrelationThreshold,
- CorrelationExpFactor: DefOptCorrelationExpFactor,
- cpuFactor: DefOptCPUFactor,
- copCPUFactor: DefOptCopCPUFactor,
- CopTiFlashConcurrencyFactor: DefOptTiFlashConcurrencyFactor,
- networkFactor: DefOptNetworkFactor,
- scanFactor: DefOptScanFactor,
- descScanFactor: DefOptDescScanFactor,
- seekFactor: DefOptSeekFactor,
- memoryFactor: DefOptMemoryFactor,
- diskFactor: DefOptDiskFactor,
- concurrencyFactor: DefOptConcurrencyFactor,
- EnableVectorizedExpression: DefEnableVectorizedExpression,
- CommandValue: uint32(mysql.ComSleep),
- TiDBOptJoinReorderThreshold: DefTiDBOptJoinReorderThreshold,
- SlowQueryFile: config.GetGlobalConfig().Log.SlowQueryFile,
- WaitSplitRegionFinish: DefTiDBWaitSplitRegionFinish,
- WaitSplitRegionTimeout: DefWaitSplitRegionTimeout,
- enableIndexMerge: DefTiDBEnableIndexMerge,
- NoopFuncsMode: TiDBOptOnOffWarn(DefTiDBEnableNoopFuncs),
- replicaRead: kv.ReplicaReadLeader,
- AllowRemoveAutoInc: DefTiDBAllowRemoveAutoInc,
- UsePlanBaselines: DefTiDBUsePlanBaselines,
- EvolvePlanBaselines: DefTiDBEvolvePlanBaselines,
- EnableExtendedStats: false,
- IsolationReadEngines: make(map[kv.StoreType]struct{}),
- LockWaitTimeout: DefInnodbLockWaitTimeout * 1000,
- MetricSchemaStep: DefTiDBMetricSchemaStep,
- MetricSchemaRangeDuration: DefTiDBMetricSchemaRangeDuration,
- SequenceState: NewSequenceState(),
- WindowingUseHighPrecision: true,
- PrevFoundInPlanCache: DefTiDBFoundInPlanCache,
- FoundInPlanCache: DefTiDBFoundInPlanCache,
- PrevFoundInBinding: DefTiDBFoundInBinding,
- FoundInBinding: DefTiDBFoundInBinding,
- SelectLimit: math.MaxUint64,
- AllowAutoRandExplicitInsert: DefTiDBAllowAutoRandExplicitInsert,
- EnableClusteredIndex: DefTiDBEnableClusteredIndex,
- EnableParallelApply: DefTiDBEnableParallelApply,
- ShardAllocateStep: DefTiDBShardAllocateStep,
- EnableAmendPessimisticTxn: DefTiDBEnableAmendPessimisticTxn,
- PartitionPruneMode: *atomic2.NewString(DefTiDBPartitionPruneMode),
- TxnScope: kv.NewDefaultTxnScopeVar(),
- EnabledRateLimitAction: DefTiDBEnableRateLimitAction,
- EnableAsyncCommit: DefTiDBEnableAsyncCommit,
- Enable1PC: DefTiDBEnable1PC,
- GuaranteeLinearizability: DefTiDBGuaranteeLinearizability,
- AnalyzeVersion: DefTiDBAnalyzeVersion,
- EnableIndexMergeJoin: DefTiDBEnableIndexMergeJoin,
- AllowFallbackToTiKV: make(map[kv.StoreType]struct{}),
- CTEMaxRecursionDepth: DefCTEMaxRecursionDepth,
- TMPTableSize: DefTiDBTmpTableMaxSize,
- MPPStoreLastFailTime: make(map[string]time.Time),
- MPPStoreFailTTL: DefTiDBMPPStoreFailTTL,
- Rng: mathutil.NewWithTime(),
- StatsLoadSyncWait: StatsLoadSyncWait.Load(),
- EnableLegacyInstanceScope: DefEnableLegacyInstanceScope,
- RemoveOrderbyInSubquery: DefTiDBRemoveOrderbyInSubquery,
- EnableSkewDistinctAgg: DefTiDBSkewDistinctAgg,
- MaxAllowedPacket: DefMaxAllowedPacket,
- TiFlashFastScan: DefTiFlashFastScan,
+ systems: make(map[string]string),
+ stmtVars: make(map[string]string),
+ PreparedStmts: make(map[uint32]interface{}),
+ PreparedStmtNameToID: make(map[string]uint32),
+ PreparedParams: make([]types.Datum, 0, 10),
+ TxnCtx: &TransactionContext{},
+ RetryInfo: &RetryInfo{},
+ ActiveRoles: make([]*auth.RoleIdentity, 0, 10),
+ StrictSQLMode: true,
+ AutoIncrementIncrement: DefAutoIncrementIncrement,
+ AutoIncrementOffset: DefAutoIncrementOffset,
+ Status: mysql.ServerStatusAutocommit,
+ StmtCtx: new(stmtctx.StatementContext),
+ AllowAggPushDown: false,
+ AllowCartesianBCJ: DefOptCartesianBCJ,
+ MPPOuterJoinFixedBuildSide: DefOptMPPOuterJoinFixedBuildSide,
+ BroadcastJoinThresholdSize: DefBroadcastJoinThresholdSize,
+ BroadcastJoinThresholdCount: DefBroadcastJoinThresholdSize,
+ OptimizerSelectivityLevel: DefTiDBOptimizerSelectivityLevel,
+ EnableOuterJoinReorder: DefTiDBEnableOuterJoinReorder,
+ RetryLimit: DefTiDBRetryLimit,
+ DisableTxnAutoRetry: DefTiDBDisableTxnAutoRetry,
+ DDLReorgPriority: kv.PriorityLow,
+ allowInSubqToJoinAndAgg: DefOptInSubqToJoinAndAgg,
+ preferRangeScan: DefOptPreferRangeScan,
+ EnableCorrelationAdjustment: DefOptEnableCorrelationAdjustment,
+ LimitPushDownThreshold: DefOptLimitPushDownThreshold,
+ CorrelationThreshold: DefOptCorrelationThreshold,
+ CorrelationExpFactor: DefOptCorrelationExpFactor,
+ cpuFactor: DefOptCPUFactor,
+ copCPUFactor: DefOptCopCPUFactor,
+ CopTiFlashConcurrencyFactor: DefOptTiFlashConcurrencyFactor,
+ networkFactor: DefOptNetworkFactor,
+ scanFactor: DefOptScanFactor,
+ descScanFactor: DefOptDescScanFactor,
+ seekFactor: DefOptSeekFactor,
+ memoryFactor: DefOptMemoryFactor,
+ diskFactor: DefOptDiskFactor,
+ concurrencyFactor: DefOptConcurrencyFactor,
+ EnableVectorizedExpression: DefEnableVectorizedExpression,
+ CommandValue: uint32(mysql.ComSleep),
+ TiDBOptJoinReorderThreshold: DefTiDBOptJoinReorderThreshold,
+ SlowQueryFile: config.GetGlobalConfig().Log.SlowQueryFile,
+ WaitSplitRegionFinish: DefTiDBWaitSplitRegionFinish,
+ WaitSplitRegionTimeout: DefWaitSplitRegionTimeout,
+ enableIndexMerge: DefTiDBEnableIndexMerge,
+ NoopFuncsMode: TiDBOptOnOffWarn(DefTiDBEnableNoopFuncs),
+ replicaRead: kv.ReplicaReadLeader,
+ AllowRemoveAutoInc: DefTiDBAllowRemoveAutoInc,
+ UsePlanBaselines: DefTiDBUsePlanBaselines,
+ EvolvePlanBaselines: DefTiDBEvolvePlanBaselines,
+ EnableExtendedStats: false,
+ IsolationReadEngines: make(map[kv.StoreType]struct{}),
+ LockWaitTimeout: DefInnodbLockWaitTimeout * 1000,
+ MetricSchemaStep: DefTiDBMetricSchemaStep,
+ MetricSchemaRangeDuration: DefTiDBMetricSchemaRangeDuration,
+ SequenceState: NewSequenceState(),
+ WindowingUseHighPrecision: true,
+ PrevFoundInPlanCache: DefTiDBFoundInPlanCache,
+ FoundInPlanCache: DefTiDBFoundInPlanCache,
+ PrevFoundInBinding: DefTiDBFoundInBinding,
+ FoundInBinding: DefTiDBFoundInBinding,
+ SelectLimit: math.MaxUint64,
+ AllowAutoRandExplicitInsert: DefTiDBAllowAutoRandExplicitInsert,
+ EnableClusteredIndex: DefTiDBEnableClusteredIndex,
+ EnableParallelApply: DefTiDBEnableParallelApply,
+ ShardAllocateStep: DefTiDBShardAllocateStep,
+ EnableAmendPessimisticTxn: DefTiDBEnableAmendPessimisticTxn,
+ PartitionPruneMode: *atomic2.NewString(DefTiDBPartitionPruneMode),
+ TxnScope: kv.NewDefaultTxnScopeVar(),
+ EnabledRateLimitAction: DefTiDBEnableRateLimitAction,
+ EnableAsyncCommit: DefTiDBEnableAsyncCommit,
+ Enable1PC: DefTiDBEnable1PC,
+ GuaranteeLinearizability: DefTiDBGuaranteeLinearizability,
+ AnalyzeVersion: DefTiDBAnalyzeVersion,
+ EnableIndexMergeJoin: DefTiDBEnableIndexMergeJoin,
+ AllowFallbackToTiKV: make(map[kv.StoreType]struct{}),
+ CTEMaxRecursionDepth: DefCTEMaxRecursionDepth,
+ TMPTableSize: DefTiDBTmpTableMaxSize,
+ MPPStoreLastFailTime: make(map[string]time.Time),
+ MPPStoreFailTTL: DefTiDBMPPStoreFailTTL,
+ Rng: mathutil.NewWithTime(),
+ StatsLoadSyncWait: StatsLoadSyncWait.Load(),
+ EnableLegacyInstanceScope: DefEnableLegacyInstanceScope,
+ RemoveOrderbyInSubquery: DefTiDBRemoveOrderbyInSubquery,
+ EnableSkewDistinctAgg: DefTiDBSkewDistinctAgg,
+ MaxAllowedPacket: DefMaxAllowedPacket,
+ TiFlashFastScan: DefTiFlashFastScan,
+ EnableTiFlashReadForWriteStmt: DefTiDBEnableTiFlashReadForWriteStmt,
  }
  vars.KVVars = tikvstore.NewVariables(&vars.Killed)
  vars.Concurrency = Concurrency{

sessionctx/variable/sysvar.go

@@ -1791,6 +1791,10 @@ var defaultSysVars = []*SysVar{
  }
  return nil
  }},
+ {Scope: ScopeGlobal | ScopeSession, Name: TiDBEnableTiFlashReadForWriteStmt, Value: BoolToOnOff(DefTiDBEnableTiFlashReadForWriteStmt), Type: TypeBool, SetSession: func(s *SessionVars, val string) error {
+ s.EnableTiFlashReadForWriteStmt = TiDBOptOn(val)
+ return nil
+ }},
 }
 
 // FeedbackProbability points to the FeedbackProbability in statistics package.

sessionctx/variable/tidb_vars.go

@@ -232,8 +232,11 @@ const (
  // RequireSecureTransport indicates the secure mode for data transport
  RequireSecureTransport = "require_secure_transport"
 
- // TiFlashFastScan indicates whether use fast scan in tiflash .
+ // TiFlashFastScan indicates whether use fast scan in tiflash.
  TiFlashFastScan = "tiflash_fastscan"
+
+ // TiDBEnableTiFlashReadForWriteStmt indicates whether to enable TiFlash to read for write statements.
+ TiDBEnableTiFlashReadForWriteStmt = "tidb_enable_tiflash_read_for_write_stmt"
 )
 
 // TiDB system variable names that both in session and global scope.
@@ -1023,6 +1026,7 @@ const (
  DefExecutorConcurrency = 5
  DefTiDBEnableGeneralPlanCache = false
  DefTiDBGeneralPlanCacheSize = 100
+ DefTiDBEnableTiFlashReadForWriteStmt = false
  // MaxDDLReorgBatchSize is exported for testing.
  MaxDDLReorgBatchSize int32 = 10240
  MinDDLReorgBatchSize int32 = 32