From ffaf2ac9eeec01d0089bc5106dfa63f6dbe8ee8f Mon Sep 17 00:00:00 2001
From: Yuanjia Zhang <zhangyuanjia@pingcap.com>
Date: Fri, 30 Dec 2022 10:20:17 +0800
Subject: [PATCH] planner: remove the unnecessary skip-plan-cache flag in
 StmtCtx (#40235)

---
 expression/builtin_compare.go       | 2 +-
 expression/util.go                  | 2 +-
 planner/core/expression_rewriter.go | 2 +-
 planner/core/plan_cache.go          | 4 ++--
 sessionctx/stmtctx/stmtctx.go       | 5 ++---
 5 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/expression/builtin_compare.go b/expression/builtin_compare.go
index 4ffd0a3dbe6be..dec5d06983679 100644
--- a/expression/builtin_compare.go
+++ b/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)
 	}
diff --git a/expression/util.go b/expression/util.go
index e19ec047e43d0..0de4253aec5f9 100644
--- a/expression/util.go
+++ b/expression/util.go
@@ -1241,7 +1241,7 @@ 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)
diff --git a/planner/core/expression_rewriter.go b/planner/core/expression_rewriter.go
index 2694d81ef0a65..5a8f8a2df9f35 100644
--- a/planner/core/expression_rewriter.go
+++ b/planner/core/expression_rewriter.go
@@ -1567,7 +1567,7 @@ func (er *expressionRewriter) inToExpression(lLen int, not bool, tp *types.Field
 					} else {
 						continue
 					}
-				} else if er.sctx.GetSessionVars().StmtCtx.SkipPlanCache {
+				} else if !er.sctx.GetSessionVars().StmtCtx.UseCache {
 					// We should remove the mutable constant for correctness, because its value may be changed.
 					expression.RemoveMutableConst(er.sctx, []expression.Expression{c})
 				}
diff --git a/planner/core/plan_cache.go b/planner/core/plan_cache.go
index 9739a63f2b8ff..8036f4067ce65 100644
--- a/planner/core/plan_cache.go
+++ b/planner/core/plan_cache.go
@@ -280,7 +280,7 @@ func generateNewPlan(ctx context.Context, sctx sessionctx.Context, isNonPrepared
 	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)
@@ -640,7 +640,7 @@ 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 (
diff --git a/sessionctx/stmtctx/stmtctx.go b/sessionctx/stmtctx/stmtctx.go
index cfe017c7c8805..01ead10e580fc 100644
--- a/sessionctx/stmtctx/stmtctx.go
+++ b/sessionctx/stmtctx/stmtctx.go
@@ -172,7 +172,6 @@ type StatementContext struct {
 	InNullRejectCheck             bool
 	AllowInvalidDate              bool
 	IgnoreNoPartition             bool
-	SkipPlanCache                 bool
 	IgnoreExplainIDSuffix         bool
 	SkipUTF8Check                 bool
 	SkipASCIICheck                bool
@@ -611,10 +610,10 @@ 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)
 }