executor: fix IsPointGet judgment condition (#10278)

executor/adapter.go

@@ -309,11 +309,11 @@ func (a *ExecStmt) buildExecutor(ctx sessionctx.Context) (Executor, error) {
 	if _, ok := a.Plan.(*plannercore.Execute); !ok {
 		// Do not sync transaction for Execute statement, because the real optimization work is done in
 		// "ExecuteExec.Build".
-		isPointGet, err := IsPointGetWithPKOrUniqueKeyByAutoCommit(ctx, a.Plan)
+		useMaxTS, err := IsPointGetWithPKOrUniqueKeyByAutoCommit(ctx, a.Plan)
 		if err != nil {
 			return nil, errors.Trace(err)
 		}
-		if isPointGet {
+		if useMaxTS {
 			logutil.Logger(context.Background()).Debug("init txnStartTS with MaxUint64", zap.Uint64("conn", ctx.GetSessionVars().ConnectionID), zap.String("text", a.Text))
 			err = ctx.InitTxnWithStartTS(math.MaxUint64)
 		}
@@ -324,7 +324,7 @@ func (a *ExecStmt) buildExecutor(ctx sessionctx.Context) (Executor, error) {
 		stmtCtx := ctx.GetSessionVars().StmtCtx
 		if stmtPri := stmtCtx.Priority; stmtPri == mysql.NoPriority {
 			switch {
-			case isPointGet:
+			case useMaxTS:
 				stmtCtx.Priority = kv.PriorityHigh
 			case a.Expensive:
 				stmtCtx.Priority = kv.PriorityLow
@@ -461,7 +461,7 @@ func (a *ExecStmt) getStatsInfo() map[string]uint64 {
 // IsPointGetWithPKOrUniqueKeyByAutoCommit returns true when meets following conditions:
 //  1. ctx is auto commit tagged
 //  2. txn is not valid
-//  2. plan is point get by pk or unique key
+//  2. plan is point get by pk, or point get by unique index (no double read)
 func IsPointGetWithPKOrUniqueKeyByAutoCommit(ctx sessionctx.Context, p plannercore.Plan) (bool, error) {
 	// check auto commit
 	if !ctx.GetSessionVars().IsAutocommit() {
@@ -489,14 +489,14 @@ func IsPointGetWithPKOrUniqueKeyByAutoCommit(ctx sessionctx.Context, p plannerco
 	case *plannercore.PhysicalIndexReader:
 		indexScan := v.IndexPlans[0].(*plannercore.PhysicalIndexScan)
 		return indexScan.IsPointGetByUniqueKey(ctx.GetSessionVars().StmtCtx), nil
-	case *plannercore.PhysicalIndexLookUpReader:
-		indexScan := v.IndexPlans[0].(*plannercore.PhysicalIndexScan)
-		return indexScan.IsPointGetByUniqueKey(ctx.GetSessionVars().StmtCtx), nil
 	case *plannercore.PhysicalTableReader:
 		tableScan := v.TablePlans[0].(*plannercore.PhysicalTableScan)
 		return len(tableScan.Ranges) == 1 && tableScan.Ranges[0].IsPoint(ctx.GetSessionVars().StmtCtx), nil
 	case *plannercore.PointGetPlan:
-		return true, nil
+		// If the PointGetPlan needs to read data using unique index (double read), we
+		// can't use max uint64, because using math.MaxUint64 can't guarantee repeatable-read
+		// and the data and index would be inconsistent!
+		return v.IndexInfo == nil, nil
 	default:
 		return false, nil
 	}

executor/executor_test.go

@@ -64,6 +64,7 @@ import (
 	"github.com/pingcap/tidb/util/testutil"
 	"github.com/pingcap/tidb/util/timeutil"
 	"github.com/pingcap/tipb/go-tipb"
+	"github.com/tiancaiamao/debugger"
 	"go.uber.org/zap"
 	"go.uber.org/zap/zapcore"
 	"golang.org/x/net/context"
@@ -1850,7 +1851,8 @@ func (s *testSuite) TestIsPointGet(c *C) {
 	tk.MustExec("use mysql")
 	ctx := tk.Se.(sessionctx.Context)
 	tests := map[string]bool{
-		"select * from help_topic where name='aaa'":         true,
+		"select * from help_topic where name='aaa'":         false,
+		"select 1 from help_topic where name='aaa'":         true,
 		"select * from help_topic where help_topic_id=1":    true,
 		"select * from help_topic where help_category_id=1": false,
 	}
@@ -1869,6 +1871,36 @@ func (s *testSuite) TestIsPointGet(c *C) {
 	}
 }
 
+func (s *testSuite) TestPointGetRepeatableRead(c *C) {
+	gofail.Enable("github.com/pingcap/tidb/executor/pointGetRepeatableReadTest1", `return(true)`)
+	gofail.Enable("github.com/pingcap/tidb/executor/pointGetRepeatableReadTest2", `return(true)`)
+	defer gofail.Disable("github.com/pingcap/tidb/executor/pointGetRepeatableReadTest1")
+	defer gofail.Disable("github.com/pingcap/tidb/executor/pointGetRepeatableReadTest2")
+
+	tk1 := testkit.NewTestKit(c, s.store)
+	tk1.MustExec("use test")
+	tk1.MustExec(`create table point_get (a int, b int, c int,
+			primary key k_a(a),
+			unique key k_b(b))`)
+	tk1.MustExec("insert into point_get values (1, 1, 1)")
+	tk2 := testkit.NewTestKit(c, s.store)
+	tk2.MustExec("use test")
+
+	go func() {
+		ctx := context.WithValue(context.Background(), "pointGetRepeatableReadTest", true)
+		rs, err := tk1.Se.Execute(ctx, "select c from point_get where b = 1")
+		c.Assert(err, IsNil)
+		result := tk1.ResultSetToResultWithCtx(ctx, rs[0], Commentf("execute sql fail"))
+		result.Check(testkit.Rows("1"))
+	}()
+
+	label := debugger.Bind("point-get-g2")
+	debugger.Continue("point-get-g1")
+	debugger.Breakpoint(label)
+	tk2.MustExec("update point_get set b = 2, c = 2 where a = 1")
+	debugger.Continue("point-get-g1")
+}
+
 func (s *testSuite) TestRow(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")

executor/point_get.go

@@ -27,6 +27,7 @@ import (
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tidb/util/codec"
+	"github.com/tiancaiamao/debugger"
 	"golang.org/x/net/context"
 )
 
@@ -71,6 +72,13 @@ func (e *PointGetExecutor) Close() error {
 	return nil
 }
 
+func dummyUseDebuggerPackageToMakeGoLintHappy() {
+	// debugger is import and used in gofail only
+	// We need to **use** it, otherwise 'make check' would complain:
+	// imported and not used: "github.com/tiancaiamao/debugger"
+	debugger.Bind("xx")
+}
+
 // Next implements the Executor interface.
 func (e *PointGetExecutor) Next(ctx context.Context, chk *chunk.Chunk) error {
 	chk.Reset()
@@ -88,6 +96,13 @@ func (e *PointGetExecutor) Next(ctx context.Context, chk *chunk.Chunk) error {
 		if err1 != nil {
 			return errors.Trace(err1)
 		}
+
+		// gofail: var pointGetRepeatableReadTest1 bool
+		// if pointGetRepeatableReadTest1 && ctx.Value("pointGetRepeatableReadTest") != nil {
+		// 	label := debugger.Bind("point-get-g1")
+		// 	debugger.Breakpoint(label)
+		// }
+
 		handleVal, err1 := e.get(idxKey)
 		if err1 != nil && !kv.ErrNotExist.Equal(err1) {
 			return errors.Trace(err1)
@@ -99,7 +114,15 @@ func (e *PointGetExecutor) Next(ctx context.Context, chk *chunk.Chunk) error {
 		if err1 != nil {
 			return errors.Trace(err1)
 		}
+
+		// gofail: var pointGetRepeatableReadTest2 bool
+		// if pointGetRepeatableReadTest2 && ctx.Value("pointGetRepeatableReadTest") != nil {
+		// 	label := debugger.Bind("point-get-g1")
+		// 	debugger.Continue("point-get-g2")
+		// 	debugger.Breakpoint(label)
+		// }
 	}
+
 	key := tablecodec.EncodeRowKeyWithHandle(e.tblInfo.ID, e.handle)
 	val, err := e.get(key)
 	if err != nil && !kv.ErrNotExist.Equal(err) {

go.mod

@@ -59,6 +59,7 @@ require (
 	github.com/prometheus/procfs v0.0.0-20180408092902-8b1c2da0d56d // indirect
 	github.com/sirupsen/logrus v0.0.0-20170323161349-3bcb09397d6d
 	github.com/spaolacci/murmur3 v0.0.0-20150829172844-0d12bf811670
+	github.com/tiancaiamao/debugger v0.0.0-20190428065433-3a10ffa41d22
 	github.com/twinj/uuid v0.0.0-20150629100731-70cac2bcd273
 	github.com/uber/jaeger-client-go v2.8.0+incompatible
 	github.com/uber/jaeger-lib v1.1.0 // indirect

go.sum

@@ -123,6 +123,8 @@ github.com/spaolacci/murmur3 v0.0.0-20150829172844-0d12bf811670/go.mod h1:JwIasO
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/tiancaiamao/debugger v0.0.0-20190428065433-3a10ffa41d22 h1:P4sgavMKEdqNOws2VfR2c/Bye9nYFgV8gHyiW1wpQhE=
+github.com/tiancaiamao/debugger v0.0.0-20190428065433-3a10ffa41d22/go.mod h1:qaShs3uDBYnvaQZJAJ6PjPg8kuAHR9zUJ8ilSLK1y/w=
 github.com/twinj/uuid v0.0.0-20150629100731-70cac2bcd273 h1:YqFyfcgqxQqjpRr0SEG0Z555J/3kPqDL/xmRyeAaX/0=
 github.com/twinj/uuid v0.0.0-20150629100731-70cac2bcd273/go.mod h1:mMgcE1RHFUFqe5AfiwlINXisXfDGro23fWdPUfOMjRY=
 github.com/uber/jaeger-client-go v2.8.0+incompatible h1:7DGH8Hqk6PirD+GE+bvCf0cLnspLuae7N1NcwMeQcyg=

util/testkit/testkit.go

@@ -183,7 +183,12 @@ func (tk *TestKit) MustQuery(sql string, args ...interface{}) *Result {
 // ResultSetToResult converts sqlexec.RecordSet to testkit.Result.
 // It is used to check results of execute statement in binary mode.
 func (tk *TestKit) ResultSetToResult(rs sqlexec.RecordSet, comment check.CommentInterface) *Result {
-	rows, err := session.GetRows4Test(context.Background(), tk.Se, rs)
+	return tk.ResultSetToResultWithCtx(context.Background(), rs, comment)
+}
+
+// ResultSetToResultWithCtx converts sqlexec.RecordSet to testkit.Result.
+func (tk *TestKit) ResultSetToResultWithCtx(ctx context.Context, rs sqlexec.RecordSet, comment check.CommentInterface) *Result {
+	rows, err := session.GetRows4Test(ctx, tk.Se, rs)
 	tk.c.Assert(errors.ErrorStack(err), check.Equals, "", comment)
 	err = rs.Close()
 	tk.c.Assert(errors.ErrorStack(err), check.Equals, "", comment)