sessionctx: support encoding and decoding statement context

executor/executor.go

@@ -1919,14 +1919,19 @@ func ResetContextOfStmt(ctx sessionctx.Context, s ast.StmtNode) (err error) {
 		sc.IgnoreTruncate = true
 		sc.IgnoreZeroInDate = true
 		sc.AllowInvalidDate = vars.SQLMode.HasAllowInvalidDatesMode()
-		if stmt.Tp == ast.ShowWarnings || stmt.Tp == ast.ShowErrors {
+		if stmt.Tp == ast.ShowWarnings || stmt.Tp == ast.ShowErrors || stmt.Tp == ast.ShowSessionStates {
 			sc.InShowWarning = true
 			sc.SetWarnings(vars.StmtCtx.GetWarnings())
 		}
 	case *ast.SplitRegionStmt:
 		sc.IgnoreTruncate = false
 		sc.IgnoreZeroInDate = true
 		sc.AllowInvalidDate = vars.SQLMode.HasAllowInvalidDatesMode()
+	case *ast.SetSessionStatesStmt:
+		sc.InSetSessionStatesStmt = true
+		sc.IgnoreTruncate = true
+		sc.IgnoreZeroInDate = true
+		sc.AllowInvalidDate = vars.SQLMode.HasAllowInvalidDatesMode()
 	default:
 		sc.IgnoreTruncate = true
 		sc.IgnoreZeroInDate = true
@@ -1945,7 +1950,7 @@ func ResetContextOfStmt(ctx sessionctx.Context, s ast.StmtNode) (err error) {
 		sc.PrevLastInsertID = vars.StmtCtx.PrevLastInsertID
 	}
 	sc.PrevAffectedRows = 0
-	if vars.StmtCtx.InUpdateStmt || vars.StmtCtx.InDeleteStmt || vars.StmtCtx.InInsertStmt {
+	if vars.StmtCtx.InUpdateStmt || vars.StmtCtx.InDeleteStmt || vars.StmtCtx.InInsertStmt || vars.StmtCtx.InSetSessionStatesStmt {
 		sc.PrevAffectedRows = int64(vars.StmtCtx.AffectedRows())
 	} else if vars.StmtCtx.InSelectStmt {
 		sc.PrevAffectedRows = -1

session/session.go

@@ -3543,15 +3543,16 @@ func (s *session) EncodeSessionStates(ctx context.Context, sctx sessionctx.Conte
 
 // DecodeSessionStates implements SessionStatesHandler.DecodeSessionStates interface.
 func (s *session) DecodeSessionStates(ctx context.Context, sctx sessionctx.Context, sessionStates *sessionstates.SessionStates) (err error) {
-	if err = s.sessionVars.DecodeSessionStates(ctx, sessionStates); err != nil {
-		return err
-	}
-
 	// Decode session variables.
 	for name, val := range sessionStates.SystemVars {
 		if err = variable.SetSessionSystemVar(s.sessionVars, name, val); err != nil {
 			return err
 		}
 	}
+
+	// Decode stmt ctx after session vars because setting session vars may override stmt ctx, such as warnings.
+	if err = s.sessionVars.DecodeSessionStates(ctx, sessionStates); err != nil {
+		return err
+	}
 	return err
 }

sessionctx/sessionstates/session_states.go

@@ -18,6 +18,7 @@ import (
 	"time"
 
 	ptypes "github.com/pingcap/tidb/parser/types"
+	"github.com/pingcap/tidb/sessionctx/stmtctx"
 	"github.com/pingcap/tidb/types"
 )
 
@@ -52,4 +53,7 @@ type SessionStates struct {
 	FoundInBinding       bool                         `json:"in-binding,omitempty"`
 	SequenceLatestValues map[int64]int64              `json:"seq-values,omitempty"`
 	MPPStoreLastFailTime map[string]time.Time         `json:"store-fail-time,omitempty"`
+	LastAffectedRows     int64                        `json:"affected-rows,omitempty"`
+	LastInsertID         uint64                       `json:"last-insert-id,omitempty"`
+	Warnings             []stmtctx.SQLWarn            `json:"warnings,omitempty"`
 }

sessionctx/sessionstates/session_states_test.go

@@ -435,6 +435,125 @@ func TestSessionCtx(t *testing.T) {
 	}
 }
 
+func TestStatementCtx(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("create table test.t1(id int auto_increment primary key, str char(1))")
+
+	tests := []struct {
+		setFunc   func(tk *testkit.TestKit) any
+		checkFunc func(tk *testkit.TestKit, param any)
+	}{
+		{
+			// check LastAffectedRows
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustQuery("show warnings")
+				return nil
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("select row_count()").Check(testkit.Rows("0"))
+				tk.MustQuery("select row_count()").Check(testkit.Rows("-1"))
+			},
+		},
+		{
+			// check LastAffectedRows
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustQuery("select 1")
+				return nil
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("select row_count()").Check(testkit.Rows("-1"))
+			},
+		},
+		{
+			// check LastAffectedRows
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustExec("insert into test.t1(str) value('a'), ('b'), ('c')")
+				return nil
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("select row_count()").Check(testkit.Rows("3"))
+				tk.MustQuery("select row_count()").Check(testkit.Rows("-1"))
+			},
+		},
+		{
+			// check LastInsertID
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("select @@last_insert_id").Check(testkit.Rows("0"))
+			},
+		},
+		{
+			// check LastInsertID
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustExec("insert into test.t1(str) value('d')")
+				rows := tk.MustQuery("select @@last_insert_id").Rows()
+				require.NotEqual(t, "0", rows[0][0].(string))
+				return rows
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("select @@last_insert_id").Check(param.([][]any))
+			},
+		},
+		{
+			// check Warning
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustQuery("select 1")
+				tk.MustQuery("show warnings").Check(testkit.Rows())
+				tk.MustQuery("show errors").Check(testkit.Rows())
+				return nil
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("show warnings").Check(testkit.Rows())
+				tk.MustQuery("show errors").Check(testkit.Rows())
+				tk.MustQuery("select @@warning_count, @@error_count").Check(testkit.Rows("0 0"))
+			},
+		},
+		{
+			// check Warning
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustGetErrCode("insert into test.t1(str) value('ef')", errno.ErrDataTooLong)
+				rows := tk.MustQuery("show warnings").Rows()
+				require.Equal(t, 1, len(rows))
+				tk.MustQuery("show errors").Check(rows)
+				return rows
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("show warnings").Check(param.([][]any))
+				tk.MustQuery("show errors").Check(param.([][]any))
+				tk.MustQuery("select @@warning_count, @@error_count").Check(testkit.Rows("1 1"))
+			},
+		},
+		{
+			// check Warning
+			setFunc: func(tk *testkit.TestKit) any {
+				tk.MustExec("set sql_mode=''")
+				tk.MustExec("insert into test.t1(str) value('ef'), ('ef')")
+				rows := tk.MustQuery("show warnings").Rows()
+				require.Equal(t, 2, len(rows))
+				tk.MustQuery("show errors").Check(testkit.Rows())
+				return rows
+			},
+			checkFunc: func(tk *testkit.TestKit, param any) {
+				tk.MustQuery("show warnings").Check(param.([][]any))
+				tk.MustQuery("show errors").Check(testkit.Rows())
+				tk.MustQuery("select @@warning_count, @@error_count").Check(testkit.Rows("2 0"))
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		tk1 := testkit.NewTestKit(t, store)
+		var param any
+		if tt.setFunc != nil {
+			param = tt.setFunc(tk1)
+		}
+		tk2 := testkit.NewTestKit(t, store)
+		showSessionStatesAndSet(t, tk1, tk2)
+		tt.checkFunc(tk2, param)
+	}
+}
+
 func showSessionStatesAndSet(t *testing.T, tk1, tk2 *testkit.TestKit) {
 	rows := tk1.MustQuery("show session_states").Rows()
 	require.Len(t, rows, 1)

sessionctx/stmtctx/stmtctx.go

@@ -15,17 +15,20 @@
 package stmtctx
 
 import (
+	"encoding/json"
 	"math"
 	"sort"
 	"strconv"
 	"sync"
 	"sync/atomic"
 	"time"
 
+	"github.com/pingcap/errors"
 	"github.com/pingcap/tidb/parser"
 	"github.com/pingcap/tidb/parser/ast"
 	"github.com/pingcap/tidb/parser/model"
 	"github.com/pingcap/tidb/parser/mysql"
+	"github.com/pingcap/tidb/parser/terror"
 	"github.com/pingcap/tidb/util/disk"
 	"github.com/pingcap/tidb/util/execdetails"
 	"github.com/pingcap/tidb/util/memory"
@@ -60,6 +63,43 @@ type SQLWarn struct {
 	Err   error
 }
 
+type jsonSQLWarn struct {
+	Level  string        `json:"level"`
+	SQLErr *terror.Error `json:"err,omitempty"`
+	Msg    string        `json:"msg,omitempty"`
+}
+
+// MarshalJSON implements the Marshaler.MarshalJSON interface.
+func (warn *SQLWarn) MarshalJSON() ([]byte, error) {
+	w := &jsonSQLWarn{
+		Level: warn.Level,
+	}
+	e := errors.Cause(warn.Err)
+	switch x := e.(type) {
+	case *terror.Error:
+		// Omit outter errors because only the most inner error matters.
+		w.SQLErr = x
+	default:
+		w.Msg = e.Error()
+	}
+	return json.Marshal(w)
+}
+
+// UnmarshalJSON implements the Unmarshaler.UnmarshalJSON interface.
+func (warn *SQLWarn) UnmarshalJSON(data []byte) error {
+	var w jsonSQLWarn
+	if err := json.Unmarshal(data, &w); err != nil {
+		return err
+	}
+	warn.Level = w.Level
+	if w.SQLErr != nil {
+		warn.Err = w.SQLErr
+	} else {
+		warn.Err = errors.New(w.Msg)
+	}
+	return nil
+}
+
 // StatementContext contains variables for a statement.
 // It should be reset before executing a statement.
 type StatementContext struct {
@@ -76,6 +116,7 @@ type StatementContext struct {
 	InLoadDataStmt         bool
 	InExplainStmt          bool
 	InCreateOrAlterStmt    bool
+	InSetSessionStatesStmt bool
 	InPreparedPlanBuilding bool
 	IgnoreTruncate         bool
 	IgnoreZeroInDate       bool
@@ -406,6 +447,13 @@ func (sc *StatementContext) AddAffectedRows(rows uint64) {
 	sc.mu.affectedRows += rows
 }
 
+// SetAffectedRows sets affected rows.
+func (sc *StatementContext) SetAffectedRows(rows uint64) {
+	sc.mu.Lock()
+	sc.mu.affectedRows = rows
+	sc.mu.Unlock()
+}
+
 // AffectedRows gets affected rows.
 func (sc *StatementContext) AffectedRows() uint64 {
 	sc.mu.Lock()
@@ -558,6 +606,7 @@ func (sc *StatementContext) SetWarnings(warns []SQLWarn) {
 	sc.mu.Lock()
 	defer sc.mu.Unlock()
 	sc.mu.warnings = warns
+	sc.mu.errorCount = 0
 	for _, w := range warns {
 		if w.Level == WarnLevelError {
 			sc.mu.errorCount++

sessionctx/stmtctx/stmtctx_test.go

@@ -16,12 +16,15 @@ package stmtctx_test
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"testing"
 	"time"
 
+	"github.com/pingcap/errors"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
+	"github.com/pingcap/tidb/sessionctx/variable"
 	"github.com/pingcap/tidb/testkit"
 	"github.com/pingcap/tidb/util/execdetails"
 	"github.com/stretchr/testify/require"
@@ -143,3 +146,43 @@ func TestWeakConsistencyRead(t *testing.T) {
 	execAndCheck("execute s", testkit.Rows("1 1 2"), kv.SI)
 	tk.MustExec("rollback")
 }
+
+func TestMarshalSQLWarn(t *testing.T) {
+	warns := []stmtctx.SQLWarn{
+		{
+			Level: stmtctx.WarnLevelError,
+			Err:   errors.New("any error"),
+		},
+		{
+			Level: stmtctx.WarnLevelError,
+			Err:   errors.Trace(errors.New("any error")),
+		},
+		{
+			Level: stmtctx.WarnLevelWarning,
+			Err:   variable.ErrUnknownSystemVar.GenWithStackByArgs("unknown"),
+		},
+		{
+			Level: stmtctx.WarnLevelWarning,
+			Err:   errors.Trace(variable.ErrUnknownSystemVar.GenWithStackByArgs("unknown")),
+		},
+	}
+
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	// First query can trigger loading global variables, which produces warnings.
+	tk.MustQuery("select 1")
+	tk.Session().GetSessionVars().StmtCtx.SetWarnings(warns)
+	rows := tk.MustQuery("show warnings").Rows()
+	require.Equal(t, len(warns), len(rows))
+
+	// The unmarshalled result doesn't need to be exactly the same with the original one.
+	// We only need that the results of `show warnings` are the same.
+	bytes, err := json.Marshal(warns)
+	require.NoError(t, err)
+	var newWarns []stmtctx.SQLWarn
+	err = json.Unmarshal(bytes, &newWarns)
+	require.NoError(t, err)
+	tk.Session().GetSessionVars().StmtCtx.SetWarnings(newWarns)
+	tk.MustQuery("show warnings").Check(rows)
+}

sessionctx/variable/session.go

@@ -1867,6 +1867,11 @@ func (s *SessionVars) EncodeSessionStates(ctx context.Context, sessionStates *se
 	sessionStates.MPPStoreLastFailTime = s.MPPStoreLastFailTime
 	sessionStates.FoundInPlanCache = s.PrevFoundInPlanCache
 	sessionStates.FoundInBinding = s.PrevFoundInBinding
+
+	// Encode StatementContext. We encode it here to avoid circle dependency.
+	sessionStates.LastAffectedRows = s.StmtCtx.PrevAffectedRows
+	sessionStates.LastInsertID = s.StmtCtx.PrevLastInsertID
+	sessionStates.Warnings = s.StmtCtx.GetWarnings()
 	return
 }
 
@@ -1902,6 +1907,11 @@ func (s *SessionVars) DecodeSessionStates(ctx context.Context, sessionStates *se
 	}
 	s.FoundInPlanCache = sessionStates.FoundInPlanCache
 	s.FoundInBinding = sessionStates.FoundInBinding
+
+	// Decode StatementContext.
+	s.StmtCtx.SetAffectedRows(uint64(sessionStates.LastAffectedRows))
+	s.StmtCtx.PrevLastInsertID = sessionStates.LastInsertID
+	s.StmtCtx.SetWarnings(sessionStates.Warnings)
 	return
 }