planner, statistics: skip plan cache for sync-load fallback plans (pingcap#67411)

close pingcap#66585

Author: winoros

pkg/planner/core/casetest/planstats/BUILD.bazel

@@ -9,7 +9,7 @@ go_test(
     ],
     data = glob(["testdata/**"]),
     flaky = True,
-    shard_count = 7,
+    shard_count = 8,
     deps = [
         "//pkg/config",
         "//pkg/domain",
@@ -25,6 +25,7 @@ go_test(
         "//pkg/sessionctx",
         "//pkg/sessionctx/stmtctx",
         "//pkg/statistics",
+        "//pkg/statistics/asyncload",
         "//pkg/statistics/handle/ddl/testutil",
         "//pkg/statistics/handle/types",
         "//pkg/testkit",

pkg/planner/core/casetest/planstats/plan_stats_test.go

@@ -37,6 +37,7 @@ import (
 	"github.com/pingcap/tidb/pkg/sessionctx"
 	"github.com/pingcap/tidb/pkg/sessionctx/stmtctx"
 	"github.com/pingcap/tidb/pkg/statistics"
+	"github.com/pingcap/tidb/pkg/statistics/asyncload"
 	"github.com/pingcap/tidb/pkg/statistics/handle/ddl/testutil"
 	"github.com/pingcap/tidb/pkg/statistics/handle/types"
 	"github.com/pingcap/tidb/pkg/testkit"
@@ -404,6 +405,85 @@ func TestPlanStatsLoadTimeout(t *testing.T) {
 	})
 }
 
+func TestPreparedPlanCacheInvalidatedAfterSyncLoadTimeoutFallback(t *testing.T) {
+	originConfig := config.GetGlobalConfig()
+	newConfig := config.NewConfig()
+	newConfig.Performance.StatsLoadConcurrency = -1 // no worker to consume channel
+	newConfig.Performance.StatsLoadQueueSize = 1
+	config.StoreGlobalConfig(newConfig)
+	t.Cleanup(func() {
+		config.StoreGlobalConfig(originConfig)
+	})
+
+	store, dom := testkit.CreateMockStoreAndDomain(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	originalPseudoTimeout := tk.MustQuery("select @@tidb_stats_load_pseudo_timeout").Rows()[0][0].(string)
+	defer func() {
+		tk.MustExec(fmt.Sprintf("set global tidb_stats_load_pseudo_timeout = %v", originalPseudoTimeout))
+	}()
+
+	oriLease := dom.StatsHandle().Lease()
+	dom.StatsHandle().SetLease(1)
+	defer func() {
+		dom.StatsHandle().SetLease(oriLease)
+	}()
+
+	tk.MustExec("set global tidb_stats_load_pseudo_timeout = 1")
+	tk.MustExec("set @@session.tidb_enable_prepared_plan_cache = 1")
+	tk.MustExec("set @@session.tidb_plan_cache_invalidation_on_fresh_stats = 1")
+	tk.MustExec("set @@session.tidb_stats_load_sync_wait = 1")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(a int primary key, b int)")
+	tk.MustExec("insert into t values (1,1),(2,2),(3,3),(4,4),(5,5)")
+	tk.MustExec("analyze table t all columns")
+	require.NoError(t, dom.StatsHandle().Update(context.Background(), dom.InfoSchema()))
+
+	tbl, err := dom.InfoSchema().TableByName(context.Background(), ast.NewCIStr("test"), ast.NewCIStr("t"))
+	require.NoError(t, err)
+	tblInfo := tbl.Meta()
+	colBID := tblInfo.Columns[1].ID
+
+	statsTbl := dom.StatsHandle().GetPhysicalTableStats(tblInfo.ID, tblInfo)
+	colBStats := statsTbl.GetCol(colBID)
+	require.NotNil(t, colBStats)
+	require.True(t, colBStats.IsAllEvicted())
+
+	tk.MustExec("prepare st from 'select * from t where b > ?'")
+	tk.MustExec("set @p = 2")
+	tk.MustExec("execute st using @p")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	// Wait for the async histogram load item corresponding to column b to be marked
+	// as sync-load failed, which confirms the sync-load path timed out and fell back
+	// to async loading for this full-load stats item.
+	require.Eventually(t, func() bool {
+		for _, item := range asyncload.AsyncLoadHistogramNeededItems.AllItems() {
+			if item.TableID == tblInfo.ID && item.ID == colBID && !item.IsIndex && item.FullLoad && item.IsSyncLoadFailed {
+				return true
+			}
+		}
+		return false
+	}, 5*time.Second, 100*time.Millisecond)
+
+	tk.MustExec("execute st using @p")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	require.Equal(t, 0, tk.Session().GetSessionPlanCache().Size())
+
+	require.NoError(t, dom.StatsHandle().LoadNeededHistograms(dom.InfoSchema()))
+	statsTbl = dom.StatsHandle().GetPhysicalTableStats(tblInfo.ID, tblInfo)
+	colBStats = statsTbl.GetCol(colBID)
+	require.NotNil(t, colBStats)
+	require.True(t, colBStats.IsFullLoad())
+
+	tk.MustExec("execute st using @p")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	require.Equal(t, 1, tk.Session().GetSessionPlanCache().Size())
+
+	tk.MustExec("execute st using @p")
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
+}
+
 func TestPlanStatsStatusRecord(t *testing.T) {
 	defer config.RestoreFunc()()
 	config.UpdateGlobal(func(conf *config.Config) {

pkg/planner/core/rule/rule_collect_plan_stats.go

@@ -39,6 +39,8 @@ import (
 // CollectPredicateColumnsPoint collects the columns that are used in the predicates.
 type CollectPredicateColumnsPoint struct{}
 
+const skipPlanCacheReasonSyncLoadFallback = "sync-load timed out and fell back to pseudo stats"
+
 // Optimize implements LogicalOptRule.<0th> interface.
 func (c *CollectPredicateColumnsPoint) Optimize(_ context.Context, plan base.LogicalPlan) (base.LogicalPlan, bool, error) {
 	planChanged := false
@@ -349,6 +351,7 @@ func RequestLoadStats(ctx base.PlanContext, neededHistItems []model.StatsLoadIte
 	if err != nil {
 		stmtCtx.IsSyncStatsFailed = true
 		if vardef.StatsLoadPseudoTimeout.Load() {
+			stmtCtx.SetSkipPlanCache(skipPlanCacheReasonSyncLoadFallback)
 			logutil.ErrVerboseLogger().Warn("RequestLoadStats failed", zap.Error(err))
 			stmtCtx.AppendWarning(err)
 			return nil
@@ -373,6 +376,7 @@ func SyncWaitStatsLoad(plan base.LogicalPlan) error {
 	if err != nil {
 		stmtCtx.IsSyncStatsFailed = true
 		if vardef.StatsLoadPseudoTimeout.Load() {
+			stmtCtx.SetSkipPlanCache(skipPlanCacheReasonSyncLoadFallback)
 			logutil.ErrVerboseLogger().Warn("SyncWaitStatsLoad failed", zap.Error(err))
 			stmtCtx.AppendWarning(err)
 			return nil