*: disable read committed isolation level

ddl/reorg.go

@@ -248,7 +248,6 @@ func (d *ddlCtx) buildDescTableScan(ctx context.Context, startTS uint64, tbl tab
 
 	builder.Request.NotFillCache = true
 	builder.Request.Priority = kv.PriorityLow
-	builder.Request.IsolationLevel = kv.SI
 
 	kvReq, err := builder.Build()
 	sctx := newContext(d.store)

distsql/request_builder.go

@@ -17,7 +17,6 @@ import (
 	"math"
 
 	"github.com/juju/errors"
-	"github.com/pingcap/tidb/ast"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/mysql"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
@@ -125,15 +124,9 @@ func (builder *RequestBuilder) SetKeepOrder(order bool) *RequestBuilder {
 	return builder
 }
 
-func (builder *RequestBuilder) getIsolationLevel(sv *variable.SessionVars) kv.IsoLevel {
-	var isoLevel string
-	if sv.TxnIsolationLevelOneShot.State == 2 {
-		isoLevel = sv.TxnIsolationLevelOneShot.Value
-	}
-	if isoLevel == "" {
-		isoLevel, _ = sv.GetSystemVar(variable.TxnIsolation)
-	}
-	if isoLevel == ast.ReadCommitted {
+func (builder *RequestBuilder) getIsolationLevel() kv.IsoLevel {
+	switch builder.Tp {
+	case kv.ReqTypeAnalyze:
 		return kv.RC
 	}
 	return kv.SI
@@ -155,7 +148,7 @@ func (builder *RequestBuilder) getKVPriority(sv *variable.SessionVars) int {
 // "Concurrency", "IsolationLevel", "NotFillCache".
 func (builder *RequestBuilder) SetFromSessionVars(sv *variable.SessionVars) *RequestBuilder {
 	builder.Request.Concurrency = sv.DistSQLScanConcurrency
-	builder.Request.IsolationLevel = builder.getIsolationLevel(sv)
+	builder.Request.IsolationLevel = builder.getIsolationLevel()
 	builder.Request.NotFillCache = sv.StmtCtx.NotFillCache
 	builder.Request.Priority = builder.getKVPriority(sv)
 	return builder

distsql/request_builder_test.go

@@ -507,7 +507,7 @@ func (s *testSuite) TestRequestBuilder5(c *C) {
 		KeepOrder:      true,
 		Desc:           false,
 		Concurrency:    15,
-		IsolationLevel: 0,
+		IsolationLevel: kv.RC,
 		Priority:       1,
 		NotFillCache:   true,
 		SyncLog:        false,

executor/analyze.go

@@ -20,7 +20,6 @@ import (
 	"github.com/juju/errors"
 	"github.com/pingcap/tidb/distsql"
 	"github.com/pingcap/tidb/domain"
-	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/metrics"
 	"github.com/pingcap/tidb/model"
 	"github.com/pingcap/tidb/mysql"
@@ -176,7 +175,6 @@ func (e *AnalyzeIndexExec) open() error {
 		SetKeepOrder(true).
 		Build()
 	kvReq.Concurrency = e.concurrency
-	kvReq.IsolationLevel = kv.RC
 	ctx := context.TODO()
 	e.result, err = distsql.Analyze(ctx, e.ctx.GetClient(), kvReq, e.ctx.GetSessionVars().KVVars)
 	if err != nil {
@@ -291,7 +289,6 @@ func (e *AnalyzeColumnsExec) buildResp(ranges []*ranger.Range) (distsql.SelectRe
 		SetAnalyzeRequest(e.analyzePB).
 		SetKeepOrder(e.keepOrder).
 		Build()
-	kvReq.IsolationLevel = kv.RC
 	kvReq.Concurrency = e.concurrency
 	if err != nil {
 		return nil, errors.Trace(err)

executor/set.go

@@ -22,7 +22,6 @@ import (
 	"github.com/pingcap/tidb/ast"
 	"github.com/pingcap/tidb/domain"
 	"github.com/pingcap/tidb/expression"
-	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/terror"
@@ -181,13 +180,6 @@ func (e *SetExecutor) setSysVariable(name string, v *expression.VarAssignment) e
 		log.Infof("con:%d %s=%s", sessionVars.ConnectionID, name, valStr)
 	}
 
-	if name == variable.TxnIsolation {
-		isoLevel, _ := sessionVars.GetSystemVar(variable.TxnIsolation)
-		if isoLevel == ast.ReadCommitted {
-			e.ctx.Txn().SetOption(kv.IsolationLevel, kv.RC)
-		}
-	}
-
 	return nil
 }
 

session/session.go

@@ -1351,10 +1351,6 @@ func (s *session) ActivePendingTxn() error {
 		return errors.Trace(err)
 	}
 	s.sessionVars.TxnCtx.StartTS = s.txn.StartTS()
-	isoLevel, _ := s.sessionVars.GetSystemVar(variable.TxnIsolation)
-	if isoLevel == ast.ReadCommitted {
-		s.txn.SetOption(kv.IsolationLevel, kv.RC)
-	}
 	return nil
 }
 

session/session_test.go

@@ -2000,7 +2000,7 @@ func (s *testSessionSuite) TestSetTransactionIsolationOneShot(c *C) {
 
 	// Check isolation level is set to read committed.
 	ctx := context.WithValue(context.Background(), "CheckSelectRequestHook", func(req *kv.Request) {
-		c.Assert(req.IsolationLevel, Equals, kv.RC)
+		c.Assert(req.IsolationLevel, Equals, kv.SI)
 	})
 	tk.Se.Execute(ctx, "select * from t where k = 1")
 

store/tikv/lock_test.go

@@ -181,22 +181,6 @@ func (s *testLockSuite) TestGetTxnStatus(c *C) {
 	c.Assert(status.IsCommitted(), IsFalse)
 }
 
-func (s *testLockSuite) TestRC(c *C) {
-	s.putKV(c, []byte("key"), []byte("v1"))
-
-	txn, err := s.store.Begin()
-	c.Assert(err, IsNil)
-	txn.Set([]byte("key"), []byte("v2"))
-	s.prewriteTxn(c, txn.(*tikvTxn))
-
-	txn2, err := s.store.Begin()
-	c.Assert(err, IsNil)
-	txn2.SetOption(kv.IsolationLevel, kv.RC)
-	val, err := txn2.Get([]byte("key"))
-	c.Assert(err, IsNil)
-	c.Assert(string(val), Equals, "v1")
-}
-
 func (s *testLockSuite) prewriteTxn(c *C, txn *tikvTxn) {
 	committer, err := newTwoPhaseCommitter(txn, 0)
 	c.Assert(err, IsNil)

store/tikv/scan.go

@@ -146,9 +146,8 @@ func (s *Scanner) getData(bo *Backoffer) error {
 				Version:  s.startTS(),
 			},
 			Context: pb.Context{
-				IsolationLevel: pbIsolationLevel(s.snapshot.isolationLevel),
-				Priority:       s.snapshot.priority,
-				NotFillCache:   s.snapshot.notFillCache,
+				Priority:     s.snapshot.priority,
+				NotFillCache: s.snapshot.notFillCache,
 			},
 		}
 		resp, err := sender.SendReq(bo, req, loc.Region, ReadTimeoutMedium)

store/tikv/snapshot.go

@@ -42,25 +42,23 @@ const (
 
 // tikvSnapshot implements the kv.Snapshot interface.
 type tikvSnapshot struct {
-	store          *tikvStore
-	version        kv.Version
-	isolationLevel kv.IsoLevel
-	priority       pb.CommandPri
-	notFillCache   bool
-	syncLog        bool
-	vars           *kv.Variables
+	store        *tikvStore
+	version      kv.Version
+	priority     pb.CommandPri
+	notFillCache bool
+	syncLog      bool
+	vars         *kv.Variables
 }
 
 var snapshotGP = gp.New(time.Minute)
 
 // newTiKVSnapshot creates a snapshot of an TiKV store.
 func newTiKVSnapshot(store *tikvStore, ver kv.Version) *tikvSnapshot {
 	return &tikvSnapshot{
-		store:          store,
-		version:        ver,
-		isolationLevel: kv.SI,
-		priority:       pb.CommandPri_Normal,
-		vars:           kv.DefaultVars,
+		store:    store,
+		version:  ver,
+		priority: pb.CommandPri_Normal,
+		vars:     kv.DefaultVars,
 	}
 }
 
@@ -151,9 +149,8 @@ func (s *tikvSnapshot) batchGetSingleRegion(bo *Backoffer, batch batchKeys, coll
 				Version: s.version.Ver,
 			},
 			Context: pb.Context{
-				Priority:       s.priority,
-				IsolationLevel: pbIsolationLevel(s.isolationLevel),
-				NotFillCache:   s.notFillCache,
+				Priority:     s.priority,
+				NotFillCache: s.notFillCache,
 			},
 		}
 		resp, err := sender.SendReq(bo, req, batch.region, ReadTimeoutMedium)
@@ -233,9 +230,8 @@ func (s *tikvSnapshot) get(bo *Backoffer, k kv.Key) ([]byte, error) {
 			Version: s.version.Ver,
 		},
 		Context: pb.Context{
-			Priority:       s.priority,
-			IsolationLevel: pbIsolationLevel(s.isolationLevel),
-			NotFillCache:   s.notFillCache,
+			Priority:     s.priority,
+			NotFillCache: s.notFillCache,
 		},
 	}
 	for {

store/tikv/txn.go

@@ -144,8 +144,6 @@ func (txn *tikvTxn) Delete(k kv.Key) error {
 func (txn *tikvTxn) SetOption(opt kv.Option, val interface{}) {
 	txn.us.SetOption(opt, val)
 	switch opt {
-	case kv.IsolationLevel:
-		txn.snapshot.isolationLevel = val.(kv.IsoLevel)
 	case kv.Priority:
 		txn.snapshot.priority = kvPriorityToCommandPri(val.(int))
 	case kv.NotFillCache:
@@ -157,9 +155,6 @@ func (txn *tikvTxn) SetOption(opt kv.Option, val interface{}) {
 
 func (txn *tikvTxn) DelOption(opt kv.Option) {
 	txn.us.DelOption(opt)
-	if opt == kv.IsolationLevel {
-		txn.snapshot.isolationLevel = kv.SI
-	}
 }
 
 func (txn *tikvTxn) Commit(ctx context.Context) error {