planner: evict all cached plans after disabling instance plan cache (#…

…57341)

ref #54057

pkg/domain/domain.go

@@ -3207,7 +3207,8 @@ func (do *Domain) planCacheEvictTrigger() {
 		case <-ticker.C:
 			// trigger the eviction
 			begin := time.Now()
-			detailInfo, numEvicted := do.instancePlanCache.Evict()
+			enabled := variable.EnableInstancePlanCache.Load()
+			detailInfo, numEvicted := do.instancePlanCache.Evict(!enabled) // evict all if the plan cache is disabled
 			metrics2.GetPlanCacheInstanceEvict().Set(float64(numEvicted))
 			if numEvicted > 0 {
 				logutil.BgLogger().Info("instance plan eviction",

pkg/planner/core/plan_cache_instance.go

@@ -134,13 +134,13 @@ func (pc *instancePlanCache) Put(key string, value, paramTypes any) (succ bool)
 // step 1: iterate all values to collect their last_used
 // step 2: estimate an eviction threshold time based on all last_used values
 // step 3: iterate all values again and evict qualified values
-func (pc *instancePlanCache) Evict() (detailInfo string, numEvicted int) {
+func (pc *instancePlanCache) Evict(evictAll bool) (detailInfo string, numEvicted int) {
 	pc.evictMutex.Lock() // make sure only one thread to trigger eviction for safety
 	defer pc.evictMutex.Unlock()
 	pc.inEvict.Store(true)
 	defer pc.inEvict.Store(false)
 	currentTot, softLimit := pc.totCost.Load(), pc.softMemLimit.Load()
-	if currentTot < softLimit {
+	if !evictAll && currentTot < softLimit {
 		detailInfo = fmt.Sprintf("memory usage is below the soft limit, currentTot: %v, softLimit: %v", currentTot, softLimit)
 		return
 	}
@@ -149,7 +149,12 @@ func (pc *instancePlanCache) Evict() (detailInfo string, numEvicted int) {
 		lastUsedTimes = append(lastUsedTimes, this.lastUsed.Load())
 		return false
 	})
-	threshold := pc.calcEvictionThreshold(lastUsedTimes) // step 2
+	var threshold time.Time
+	if evictAll {
+		threshold = time.Now().Add(time.Hour * 24) // a future time
+	} else {
+		threshold = pc.calcEvictionThreshold(lastUsedTimes) // step 2
+	}
 	detailInfo = fmt.Sprintf("evict threshold: %v", threshold)
 	pc.foreach(func(prev, this *instancePCNode) bool { // step 3
 		if !this.lastUsed.Load().After(threshold) { // if lastUsed<=threshold, evict this value

pkg/planner/core/plan_cache_instance_test.go

@@ -84,7 +84,7 @@ func TestInstancePlanCacheBasic(t *testing.T) {
 	_hit(t, pc, 1, 0) // access 1-3 to refresh their last_used
 	_hit(t, pc, 2, 0)
 	_hit(t, pc, 3, 0)
-	_, numEvicted := pc.Evict()
+	_, numEvicted := pc.Evict(false)
 	require.Equal(t, numEvicted > 0, true)
 	require.Equal(t, pc.MemUsage(), int64(300))
 	_hit(t, pc, 1, 0) // access 1-3 to refresh their last_used
@@ -98,7 +98,7 @@ func TestInstancePlanCacheBasic(t *testing.T) {
 	_put(pc, 1, 100, 0)
 	_put(pc, 2, 100, 0)
 	_put(pc, 3, 100, 0)
-	_, numEvicted = pc.Evict()
+	_, numEvicted = pc.Evict(false)
 	require.Equal(t, numEvicted > 0, false)
 	require.Equal(t, pc.MemUsage(), int64(300))
 	_hit(t, pc, 1, 0)
@@ -115,7 +115,7 @@ func TestInstancePlanCacheBasic(t *testing.T) {
 	numHeads := 0
 	pcImpl.heads.Range(func(k, v any) bool { numHeads++; return true })
 	require.Equal(t, numHeads, 3)
-	_, numEvicted = pc.Evict()
+	_, numEvicted = pc.Evict(false)
 	require.Equal(t, numEvicted > 0, true)
 	require.Equal(t, pc.MemUsage(), int64(0))
 	numHeads = 0
@@ -177,7 +177,7 @@ func TestInstancePlanCacheWithMatchOpts(t *testing.T) {
 	_hit(t, pc, 1, 1) // refresh 1-3's last_used
 	_hit(t, pc, 1, 2)
 	_hit(t, pc, 1, 3)
-	_, numEvicted := pc.Evict()
+	_, numEvicted := pc.Evict(false)
 	require.True(t, numEvicted > 0)
 	require.Equal(t, pc.MemUsage(), int64(300))
 	_hit(t, pc, 1, 1)
@@ -187,6 +187,27 @@ func TestInstancePlanCacheWithMatchOpts(t *testing.T) {
 	_miss(t, pc, 1, 5)
 }
 
+func TestInstancePlanCacheEvictAll(t *testing.T) {
+	sctx := MockContext()
+	defer func() {
+		domain.GetDomain(sctx).StatsHandle().Close()
+	}()
+	sctx.GetSessionVars().PlanCacheInvalidationOnFreshStats = true
+
+	// same key with different statsHash
+	pc := NewInstancePlanCache(1000, 1000)
+	_put(pc, 1, 100, 1)
+	_put(pc, 1, 100, 2)
+	_put(pc, 1, 100, 3)
+	_, numEvicted := pc.Evict(true)
+	require.Equal(t, 3, numEvicted)
+	_miss(t, pc, 1, 1)
+	_miss(t, pc, 1, 2)
+	_miss(t, pc, 1, 3)
+	require.Equal(t, pc.MemUsage(), int64(0))
+	require.Equal(t, pc.Size(), int64(0))
+}
+
 func TestInstancePlanCacheConcurrentRead(t *testing.T) {
 	sctx := MockContext()
 	defer func() {

pkg/sessionctx/context.go

@@ -68,7 +68,7 @@ type InstancePlanCache interface {
 	// Put puts the key and value into the cache.
 	Put(key string, value, paramTypes any) (succ bool)
 	// Evict evicts some cached values.
-	Evict() (detailInfo string, numEvicted int)
+	Evict(evictAll bool) (detailInfo string, numEvicted int)
 	// Size returns the number of cached values.
 	Size() int64
 	// MemUsage returns the total memory usage of this plan cache.