planner: remove userVarType in session variables

executor/set.go

@@ -92,7 +92,6 @@ func (e *SetExecutor) Next(ctx context.Context, req *chunk.Chunk) error {
 				sessionVars.UnsetUserVar(name)
 			} else {
 				sessionVars.Users[name] = value
-				sessionVars.UserVarTypes[name] = v.Expr.GetType()
 			}
 			sessionVars.UsersLock.Unlock()
 			continue

expression/builtin_other_test.go

@@ -136,14 +136,6 @@ func TestGetVar(t *testing.T) {
 	}
 	for _, kv := range sessionVars {
 		ctx.GetSessionVars().Users[kv.key] = types.NewDatum(kv.val)
-		var tp *types.FieldType
-		if _, ok := kv.val.(types.Time); ok {
-			tp = types.NewFieldType(mysql.TypeDatetime)
-		} else {
-			tp = types.NewFieldType(mysql.TypeVarString)
-		}
-		types.DefaultParamTypeForValue(kv.val, tp)
-		ctx.GetSessionVars().UserVarTypes[kv.key] = tp
 	}
 
 	testCases := []struct {
@@ -160,9 +152,12 @@ func TestGetVar(t *testing.T) {
 		{[]interface{}{"h"}, timeDec.String()},
 	}
 	for _, tc := range testCases {
-		tp, ok := ctx.GetSessionVars().UserVarTypes[tc.args[0].(string)]
+		userVar, ok := ctx.GetSessionVars().Users[tc.args[0].(string)]
+		tp := new(types.FieldType)
 		if !ok {
 			tp = types.NewFieldType(mysql.TypeVarString)
+		} else {
+			types.DefaultParamTypeForValue(userVar.GetValue(), tp)
 		}
 		fn, err := BuildGetVarFunction(ctx, datumsToConstants(types.MakeDatums(tc.args...))[0], tp)
 		require.NoError(t, err)

planner/core/expression_rewriter.go

@@ -1279,17 +1279,17 @@ func (er *expressionRewriter) rewriteVariable(v *ast.VariableExpr) {
 			// Store the field type of the variable into SessionVars.UserVarTypes.
 			// Normally we can infer the type from SessionVars.User, but we need SessionVars.UserVarTypes when
 			// GetVar has not been executed to fill the SessionVars.Users.
-			sessionVars.UsersLock.Lock()
-			sessionVars.UserVarTypes[name] = tp
-			sessionVars.UsersLock.Unlock()
 			return
 		}
 		sessionVars.UsersLock.RLock()
-		tp, ok := sessionVars.UserVarTypes[name]
+		userVar, ok := sessionVars.Users[name]
 		sessionVars.UsersLock.RUnlock()
+		tp := new(types.FieldType)
 		if !ok {
 			tp = types.NewFieldType(mysql.TypeVarString)
 			tp.SetFlen(mysql.MaxFieldVarCharLength)
+		} else {
+			types.DefaultParamTypeForValue(userVar.GetValue(), tp)
 		}
 		f, err := er.newFunction(ast.GetVar, tp, expression.DatumToConstant(types.NewStringDatum(name), mysql.TypeString, 0))
 		if err != nil {

planner/core/plan_cache.go

@@ -102,9 +102,12 @@ func parseParamTypes(sctx sessionctx.Context, params []expression.Expression) (p
 
 		// from text protocol, there must be a GetVar function
 		name := param.(*expression.ScalarFunction).GetArgs()[0].String()
-		tp := sctx.GetSessionVars().UserVarTypes[name]
-		if tp == nil {
+		userVar, ok := sctx.GetSessionVars().Users[name]
+		tp := new(types.FieldType)
+		if !ok {
 			tp = types.NewFieldType(mysql.TypeNull)
+		} else {
+			types.DefaultParamTypeForValue(userVar.GetValue(), tp)
 		}
 		paramTypes = append(paramTypes, tp)
 	}

sessionctx/variable/session.go

@@ -40,7 +40,6 @@ import (
 	"github.com/pingcap/tidb/parser/charset"
 	"github.com/pingcap/tidb/parser/model"
 	"github.com/pingcap/tidb/parser/mysql"
-	ptypes "github.com/pingcap/tidb/parser/types"
 	"github.com/pingcap/tidb/sessionctx/sessionstates"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
 	pumpcli "github.com/pingcap/tidb/tidb-binlog/pump_client"
@@ -565,7 +564,7 @@ type SessionVars struct {
 	Users map[string]types.Datum
 	// UserVarTypes stores the FieldType for user variables, it cannot be inferred from Users when Users have not been set yet.
 	// It is read/write protected by UsersLock.
-	UserVarTypes map[string]*types.FieldType
+	//UserVarTypes map[string]*types.FieldType
 	// systems variables, don't modify it directly, use GetSystemVar/SetSystemVar method.
 	systems map[string]string
 	// stmtVars variables are temporarily set by SET_VAR hint
@@ -1363,7 +1362,6 @@ func (connInfo *ConnectionInfo) IsSecureTransport() bool {
 func NewSessionVars() *SessionVars {
 	vars := &SessionVars{
 		Users:                       make(map[string]types.Datum),
-		UserVarTypes:                make(map[string]*types.FieldType),
 		systems:                     make(map[string]string),
 		stmtVars:                    make(map[string]string),
 		PreparedStmts:               make(map[uint32]interface{}),
@@ -1643,7 +1641,6 @@ func (s *SessionVars) SetUserVar(varName string, svalue string, collation string
 func (s *SessionVars) UnsetUserVar(varName string) {
 	varName = strings.ToLower(varName)
 	delete(s.Users, varName)
-	delete(s.UserVarTypes, varName)
 }
 
 // SetLastInsertID saves the last insert id to the session context.
@@ -2005,10 +2002,6 @@ func (s *SessionVars) EncodeSessionStates(ctx context.Context, sessionStates *se
 	for name, userVar := range s.Users {
 		sessionStates.UserVars[name] = userVar.Clone()
 	}
-	sessionStates.UserVarTypes = make(map[string]*ptypes.FieldType, len(s.UserVarTypes))
-	for name, userVarType := range s.UserVarTypes {
-		sessionStates.UserVarTypes[name] = userVarType.Clone()
-	}
 	s.UsersLock.RUnlock()
 
 	// Encode other session contexts.
@@ -2043,10 +2036,6 @@ func (s *SessionVars) DecodeSessionStates(ctx context.Context, sessionStates *se
 	for name, userVar := range sessionStates.UserVars {
 		s.Users[name] = *userVar.Clone()
 	}
-	s.UserVarTypes = make(map[string]*ptypes.FieldType, len(sessionStates.UserVarTypes))
-	for name, userVarType := range sessionStates.UserVarTypes {
-		s.UserVarTypes[name] = userVarType.Clone()
-	}
 	s.UsersLock.Unlock()
 
 	// Decode other session contexts.