planner: remove the unnecessary skip-plan-cache flag in StmtCtx (#40235)

expression/builtin_compare.go

@@ -1586,7 +1586,7 @@ func (c *compareFunctionClass) refineArgs(ctx sessionctx.Context, args []Express
 		} else {
 			return args
 		}
-	} else if ctx.GetSessionVars().StmtCtx.SkipPlanCache {
+	} else if !ctx.GetSessionVars().StmtCtx.UseCache {
 		// We should remove the mutable constant for correctness, because its value may be changed.
 		RemoveMutableConst(ctx, args)
 	}

expression/expression.go

@@ -816,8 +816,7 @@ func SplitDNFItems(onExpr Expression) []Expression {
 // If the Expression is a non-constant value, it means the result is unknown.
 func EvaluateExprWithNull(ctx sessionctx.Context, schema *Schema, expr Expression) Expression {
 	if MaybeOverOptimized4PlanCache(ctx, []Expression{expr}) {
-		ctx.GetSessionVars().StmtCtx.SkipPlanCache = true
-		ctx.GetSessionVars().StmtCtx.AppendWarning(errors.New("skip plan-cache: %v affects null check"))
+		ctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.New("skip plan-cache: %v affects null check"))
 	}
 	if ctx.GetSessionVars().StmtCtx.InNullRejectCheck {
 		expr, _ = evaluateExprWithNullInNullRejectCheck(ctx, schema, expr)

expression/expression_test.go

@@ -77,7 +77,7 @@ func TestEvaluateExprWithNullAndParameters(t *testing.T) {
 	res = EvaluateExprWithNull(ctx, schema, ltWithParam)
 	_, isConst := res.(*Constant)
 	require.True(t, isConst) // this expression is evaluated and skip-plan cache flag is set.
-	require.True(t, ctx.GetSessionVars().StmtCtx.SkipPlanCache)
+	require.False(t, ctx.GetSessionVars().StmtCtx.UseCache)
 }
 
 func TestEvaluateExprWithNullNoChangeRetType(t *testing.T) {

expression/util.go

@@ -1239,7 +1239,7 @@ func ContainCorrelatedColumn(exprs []Expression) bool {
 // TODO: Do more careful check here.
 func MaybeOverOptimized4PlanCache(ctx sessionctx.Context, exprs []Expression) bool {
 	// If we do not enable plan cache, all the optimization can work correctly.
-	if !ctx.GetSessionVars().StmtCtx.UseCache || ctx.GetSessionVars().StmtCtx.SkipPlanCache {
+	if !ctx.GetSessionVars().StmtCtx.UseCache {
 		return false
 	}
 	return containMutableConst(ctx, exprs)

planner/core/plan_cache.go

@@ -276,7 +276,7 @@ func generateNewPlan(ctx context.Context, sctx sessionctx.Context, isGeneralPlan
 	if containTableDual(p) && paramNum > 0 {
 		stmtCtx.SetSkipPlanCache(errors.New("skip plan-cache: get a TableDual plan"))
 	}
-	if stmtAst.UseCache && !stmtCtx.SkipPlanCache && !ignorePlanCache {
+	if stmtCtx.UseCache && !ignorePlanCache {
 		// rebuild key to exclude kv.TiFlash when stmt is not read only
 		if _, isolationReadContainTiFlash := sessVars.IsolationReadEngines[kv.TiFlash]; isolationReadContainTiFlash && !IsReadOnly(stmtAst.Stmt, sessVars) {
 			delete(sessVars.IsolationReadEngines, kv.TiFlash)
@@ -636,7 +636,7 @@ func CheckPreparedPriv(sctx sessionctx.Context, stmt *PlanCacheStmt, is infosche
 // short paths for these executions, currently "point select" and "point update"
 func tryCachePointPlan(_ context.Context, sctx sessionctx.Context,
 	stmt *PlanCacheStmt, _ infoschema.InfoSchema, p Plan) error {
-	if !sctx.GetSessionVars().StmtCtx.UseCache || sctx.GetSessionVars().StmtCtx.SkipPlanCache {
+	if !sctx.GetSessionVars().StmtCtx.UseCache {
 		return nil
 	}
 	var (

sessionctx/stmtctx/stmtctx.go

@@ -171,7 +171,6 @@ type StatementContext struct {
 	InNullRejectCheck             bool
 	AllowInvalidDate              bool
 	IgnoreNoPartition             bool
-	SkipPlanCache                 bool
 	IgnoreExplainIDSuffix         bool
 	SkipUTF8Check                 bool
 	SkipASCIICheck                bool
@@ -599,10 +598,10 @@ func (sc *StatementContext) SetPlanHint(hint string) {
 
 // SetSkipPlanCache sets to skip the plan cache and records the reason.
 func (sc *StatementContext) SetSkipPlanCache(reason error) {
-	if sc.UseCache && sc.SkipPlanCache {
+	if !sc.UseCache {
 		return // avoid unnecessary warnings
 	}
-	sc.SkipPlanCache = true
+	sc.UseCache = false
 	sc.AppendWarning(reason)
 }
 

util/ranger/detacher.go

@@ -582,8 +582,7 @@ func ExtractEqAndInCondition(sctx sessionctx.Context, conditions []expression.Ex
 		if len(points[offset]) == 0 { // Early termination if false expression found
 			if expression.MaybeOverOptimized4PlanCache(sctx, conditions) {
 				// `a>@x and a<@y` --> `invalid-range if @x>=@y`
-				sctx.GetSessionVars().StmtCtx.SkipPlanCache = true
-				sctx.GetSessionVars().StmtCtx.AppendWarning(errors.Errorf("skip plan-cache: some parameters may be overwritten"))
+				sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: some parameters may be overwritten"))
 			}
 			return nil, nil, nil, nil, true
 		}
@@ -607,8 +606,7 @@ func ExtractEqAndInCondition(sctx sessionctx.Context, conditions []expression.Ex
 		} else if len(points[i]) == 0 { // Early termination if false expression found
 			if expression.MaybeOverOptimized4PlanCache(sctx, conditions) {
 				// `a>@x and a<@y` --> `invalid-range if @x>=@y`
-				sctx.GetSessionVars().StmtCtx.SkipPlanCache = true
-				sctx.GetSessionVars().StmtCtx.AppendWarning(errors.Errorf("skip plan-cache: some parameters may be overwritten"))
+				sctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.Errorf("skip plan-cache: some parameters may be overwritten"))
 			}
 			return nil, nil, nil, nil, true
 		} else {