From 87999d1d4ac60b0242701418c809ee6177e93ed5 Mon Sep 17 00:00:00 2001
From: Yuanjia Zhang <zhangyuanjia@pingcap.com>
Date: Wed, 29 May 2024 17:23:51 +0800
Subject: [PATCH] planner: fix small regression caused by #53094 (#53646)

ref pingcap/tidb#50618
---
 pkg/planner/core/plan_cache.go       | 39 ++++++++++++++++------------
 pkg/planner/core/plan_cache_lru.go   |  4 +++
 pkg/planner/core/plan_cache_utils.go |  4 +--
 3 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/pkg/planner/core/plan_cache.go b/pkg/planner/core/plan_cache.go
index c2ca1ff8d250b..6ad798d3f80e3 100644
--- a/pkg/planner/core/plan_cache.go
+++ b/pkg/planner/core/plan_cache.go
@@ -215,32 +215,39 @@ func GetPlanFromSessionPlanCache(ctx context.Context, sctx sessionctx.Context,
 		}
 	}
 
-	matchOpts, err := GetMatchOpts(sctx, is, stmt, params)
-	if err != nil {
-		return nil, nil, err
-	}
+	var matchOpts *utilpc.PlanCacheMatchOpts
 	if stmtCtx.UseCache() {
-		if plan, names, ok, err := getCachedPlan(sctx, isNonPrepared, cacheKey, bindSQL, is, stmt, matchOpts); err != nil || ok {
-			return plan, names, err
+		var cacheVal kvcache.Value
+		var hit, isPointPlan bool
+		if stmt.PointGet.Executor != nil { // if it's PointGet Plan, no need to use MatchOpts
+			cacheVal, hit = sctx.GetSessionPlanCache().Get(cacheKey, nil)
+			isPointPlan = true
+		} else {
+			matchOpts = GetMatchOpts(sctx, is, stmt, params)
+			cacheVal, hit = sctx.GetSessionPlanCache().Get(cacheKey, matchOpts)
+		}
+		if hit {
+			if plan, names, ok, err := adjustCachedPlan(sctx, cacheVal.(*PlanCacheValue), isNonPrepared, isPointPlan, cacheKey, bindSQL, is, stmt); err != nil || ok {
+				return plan, names, err
+			}
 		}
 	}
+	if matchOpts == nil {
+		matchOpts = GetMatchOpts(sctx, is, stmt, params)
+	}
 
 	return generateNewPlan(ctx, sctx, isNonPrepared, is, stmt, cacheKey, latestSchemaVersion, bindSQL, matchOpts)
 }
 
-func getCachedPlan(sctx sessionctx.Context, isNonPrepared bool, cacheKey kvcache.Key, bindSQL string,
-	is infoschema.InfoSchema, stmt *PlanCacheStmt, matchOpts *utilpc.PlanCacheMatchOpts) (base.Plan,
+func adjustCachedPlan(sctx sessionctx.Context, cachedVal *PlanCacheValue, isNonPrepared, isPointPlan bool,
+	cacheKey kvcache.Key, bindSQL string, is infoschema.InfoSchema, stmt *PlanCacheStmt) (base.Plan,
 	[]*types.FieldName, bool, error) {
 	sessVars := sctx.GetSessionVars()
 	stmtCtx := sessVars.StmtCtx
-
-	candidate, exist := sctx.GetSessionPlanCache().Get(cacheKey, matchOpts)
-	if !exist {
-		return nil, nil, false, nil
-	}
-	cachedVal := candidate.(*PlanCacheValue)
-	if err := checkPreparedPriv(sctx, stmt, is); err != nil {
-		return nil, nil, false, err
+	if !isPointPlan { // keep the prior behavior
+		if err := checkPreparedPriv(sctx, stmt, is); err != nil {
+			return nil, nil, false, err
+		}
 	}
 	for tblInfo, unionScan := range cachedVal.TblInfo2UnionScan {
 		if !unionScan && tableHasDirtyContent(sctx.GetPlanCtx(), tblInfo) {
diff --git a/pkg/planner/core/plan_cache_lru.go b/pkg/planner/core/plan_cache_lru.go
index ce74307738e29..6be81eac0246e 100644
--- a/pkg/planner/core/plan_cache_lru.go
+++ b/pkg/planner/core/plan_cache_lru.go
@@ -253,6 +253,10 @@ func (l *LRUPlanCache) memoryControl() {
 // PickPlanFromBucket pick one plan from bucket
 func (l *LRUPlanCache) pickFromBucket(bucket map[*list.Element]struct{}, matchOpts *utilpc.PlanCacheMatchOpts) (*list.Element, bool) {
 	for k := range bucket {
+		if matchOpts == nil { // for PointGet Plan
+			return k, true
+		}
+
 		plan := k.Value.(*planCacheEntry).PlanValue.(*PlanCacheValue)
 		// check param types' compatibility
 		ok1 := checkTypesCompatibility4PC(plan.matchOpts.ParamTypes, matchOpts.ParamTypes)
diff --git a/pkg/planner/core/plan_cache_utils.go b/pkg/planner/core/plan_cache_utils.go
index 7909f35921787..c5833c11a89bb 100644
--- a/pkg/planner/core/plan_cache_utils.go
+++ b/pkg/planner/core/plan_cache_utils.go
@@ -559,7 +559,7 @@ func GetPreparedStmt(stmt *ast.ExecuteStmt, vars *variable.SessionVars) (*PlanCa
 
 // GetMatchOpts get options to fetch plan or generate new plan
 // we can add more options here
-func GetMatchOpts(sctx sessionctx.Context, is infoschema.InfoSchema, stmt *PlanCacheStmt, params []expression.Expression) (*utilpc.PlanCacheMatchOpts, error) {
+func GetMatchOpts(sctx sessionctx.Context, is infoschema.InfoSchema, stmt *PlanCacheStmt, params []expression.Expression) *utilpc.PlanCacheMatchOpts {
 	var statsVerHash uint64
 	var limitOffsetAndCount []uint64
 
@@ -606,7 +606,7 @@ func GetMatchOpts(sctx sessionctx.Context, is infoschema.InfoSchema, stmt *PlanC
 		StatsVersionHash:    statsVerHash,
 		ParamTypes:          parseParamTypes(sctx, params),
 		ForeignKeyChecks:    sctx.GetSessionVars().ForeignKeyChecks,
-	}, nil
+	}
 }
 
 // CheckTypesCompatibility4PC compares FieldSlice with []*types.FieldType