statistics: update the global stats correctly after truncate a partition

pkg/statistics/handle/ddl/BUILD.bazel

@@ -5,6 +5,7 @@ go_library(
     srcs = [
         "ddl.go",
         "exchange_partition.go",
+        "truncate_partition.go",
     ],
     importpath = "github.com/pingcap/tidb/pkg/statistics/handle/ddl",
     visibility = ["//visibility:public"],
@@ -28,7 +29,7 @@ go_test(
     timeout = "short",
     srcs = ["ddl_test.go"],
     flaky = True,
-    shard_count = 6,
+    shard_count = 8,
     deps = [
         "//pkg/parser/model",
         "//pkg/planner/cardinality",

pkg/statistics/handle/ddl/ddl.go

@@ -116,11 +116,8 @@ func (h *ddlHandlerImpl) HandleDDLEvent(t *util.DDLEvent) error {
 			}
 		}
 	case model.ActionTruncateTablePartition:
-		globalTableInfo, addedPartInfo, _ := t.GetTruncatePartitionInfo()
-		for _, def := range addedPartInfo.Definitions {
-			if err := h.statsWriter.InsertTableStats2KV(globalTableInfo, def.ID); err != nil {
-				return err
-			}
+		if err := h.onTruncatePartitions(t); err != nil {
+			return err
 		}
 	case model.ActionDropTablePartition:
 		globalTableInfo, droppedPartitionInfo := t.GetDropPartitionInfo()

pkg/statistics/handle/ddl/ddl_test.go

@@ -255,21 +255,6 @@ PARTITION BY RANGE ( a ) (
 			require.False(t, statsTbl.Pseudo)
 		}
 
-		truncatePartition := "alter table t truncate partition p4"
-		testKit.MustExec(truncatePartition)
-		is = do.InfoSchema()
-		tbl, err = is.TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
-		require.NoError(t, err)
-		tableInfo = tbl.Meta()
-		err = h.HandleDDLEvent(<-h.DDLEventCh())
-		require.NoError(t, err)
-		require.Nil(t, h.Update(is))
-		pi = tableInfo.GetPartitionInfo()
-		for _, def := range pi.Definitions {
-			statsTbl := h.GetPartitionStats(tableInfo, def.ID)
-			require.False(t, statsTbl.Pseudo)
-		}
-
 		reorganizePartition := "alter table t reorganize partition p0,p1 into (partition p0 values less than (11))"
 		testKit.MustExec(reorganizePartition)
 		is = do.InfoSchema()
@@ -287,6 +272,158 @@ PARTITION BY RANGE ( a ) (
 	}
 }
 
+func TestTruncateAPartition(t *testing.T) {
+	store, do := testkit.CreateMockStoreAndDomain(t)
+	testKit := testkit.NewTestKit(t, store)
+	h := do.StatsHandle()
+	testKit.MustExec("use test")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec(`
+		create table t (
+			a int,
+			b int,
+			primary key(a),
+			index idx(b)
+		)
+		partition by range (a) (
+			partition p0 values less than (6),
+			partition p1 values less than (11),
+			partition p2 values less than (16),
+			partition p3 values less than (21)
+		)
+	`)
+	testKit.MustExec("insert into t values (1,2),(2,2),(6,2),(11,2),(16,2)")
+	testKit.MustExec("analyze table t")
+	is := do.InfoSchema()
+	tbl, err := is.TableByName(
+		model.NewCIStr("test"), model.NewCIStr("t"),
+	)
+	require.NoError(t, err)
+	tableInfo := tbl.Meta()
+	pi := tableInfo.GetPartitionInfo()
+	for _, def := range pi.Definitions {
+		statsTbl := h.GetPartitionStats(tableInfo, def.ID)
+		require.False(t, statsTbl.Pseudo)
+	}
+	err = h.Update(is)
+	require.NoError(t, err)
+
+	// Get partition p0's stats update version.
+	partitionID := pi.Definitions[0].ID
+	// Get it from stats_meat first.
+	rows := testKit.MustQuery(
+		"select version from mysql.stats_meta where table_id = ?", partitionID,
+	).Rows()
+	require.Len(t, rows, 1)
+	version := rows[0][0].(string)
+
+	testKit.MustExec("alter table t truncate partition p0")
+	// Find the truncate partition event.
+	var truncatePartitionEvent *util.DDLEvent
+	for {
+		event := <-h.DDLEventCh()
+		if event.GetType() == model.ActionTruncateTablePartition {
+			truncatePartitionEvent = event
+			break
+		}
+	}
+	err = h.HandleDDLEvent(truncatePartitionEvent)
+	require.NoError(t, err)
+	// Check global stats meta.
+	// Because we have truncated a partition, the count should be 5 - 2 = 3 and the modify count should be 2.
+	testKit.MustQuery(
+		"select count, modify_count from mysql.stats_meta where table_id = ?", tableInfo.ID,
+	).Check(
+		testkit.Rows("3 2"),
+	)
+
+	// Check the version again.
+	rows = testKit.MustQuery(
+		"select version from mysql.stats_meta where table_id = ?", partitionID,
+	).Rows()
+	require.Len(t, rows, 1)
+	// Version gets updated after truncate the partition.
+	require.NotEqual(t, version, rows[0][0].(string))
+}
+
+func TestTruncatePartitions(t *testing.T) {
+	store, do := testkit.CreateMockStoreAndDomain(t)
+	testKit := testkit.NewTestKit(t, store)
+	h := do.StatsHandle()
+	testKit.MustExec("use test")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec(`
+		create table t (
+			a int,
+			b int,
+			primary key(a),
+			index idx(b)
+		)
+		partition by range (a) (
+			partition p0 values less than (6),
+			partition p1 values less than (11),
+			partition p2 values less than (16),
+			partition p3 values less than (21)
+		)
+	`)
+	testKit.MustExec("insert into t values (1,2),(2,2),(6,2),(11,2),(16,2)")
+	testKit.MustExec("analyze table t")
+	is := do.InfoSchema()
+	tbl, err := is.TableByName(
+		model.NewCIStr("test"), model.NewCIStr("t"),
+	)
+	require.NoError(t, err)
+	tableInfo := tbl.Meta()
+	pi := tableInfo.GetPartitionInfo()
+	for _, def := range pi.Definitions {
+		statsTbl := h.GetPartitionStats(tableInfo, def.ID)
+		require.False(t, statsTbl.Pseudo)
+	}
+	err = h.Update(is)
+	require.NoError(t, err)
+
+	// Get partition p0 and p1's stats update version.
+	partitionP0ID := pi.Definitions[0].ID
+	partitionP1ID := pi.Definitions[1].ID
+	// Get it from stats_meat first.
+	rows := testKit.MustQuery(
+		"select version from mysql.stats_meta where table_id in (?, ?)", partitionP0ID, partitionP1ID,
+	).Rows()
+	require.Len(t, rows, 2)
+	versionP0 := rows[0][0].(string)
+	versionP1 := rows[1][0].(string)
+
+	// Truncate two partitions.
+	testKit.MustExec("alter table t truncate partition p0, p1")
+	// Find the truncate partition event.
+	var truncatePartitionEvent *util.DDLEvent
+	for {
+		event := <-h.DDLEventCh()
+		if event.GetType() == model.ActionTruncateTablePartition {
+			truncatePartitionEvent = event
+			break
+		}
+	}
+	err = h.HandleDDLEvent(truncatePartitionEvent)
+	require.NoError(t, err)
+	// Check global stats meta.
+	// Because we have truncated two partitions, the count should be 5 - 2 - 1  = 2 and the modify count should be 3.
+	testKit.MustQuery(
+		"select count, modify_count from mysql.stats_meta where table_id = ?", tableInfo.ID,
+	).Check(
+		testkit.Rows("2 3"),
+	)
+
+	// Check the version again.
+	rows = testKit.MustQuery(
+		"select version from mysql.stats_meta where table_id in (?, ?)", partitionP0ID, partitionP1ID,
+	).Rows()
+	require.Len(t, rows, 2)
+	// Version gets updated after truncate the partition.
+	require.NotEqual(t, versionP0, rows[0][0].(string))
+	require.NotEqual(t, versionP1, rows[1][0].(string))
+}
+
 func TestDropAPartition(t *testing.T) {
 	store, do := testkit.CreateMockStoreAndDomain(t)
 	testKit := testkit.NewTestKit(t, store)

pkg/statistics/handle/ddl/truncate_partition.go

@@ -0,0 +1,161 @@
+// Copyright 2023 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ddl
+
+import (
+	"github.com/pingcap/errors"
+	"github.com/pingcap/tidb/pkg/infoschema"
+	"github.com/pingcap/tidb/pkg/parser/model"
+	"github.com/pingcap/tidb/pkg/sessionctx"
+	"github.com/pingcap/tidb/pkg/sessionctx/variable"
+	"github.com/pingcap/tidb/pkg/statistics/handle/lockstats"
+	"github.com/pingcap/tidb/pkg/statistics/handle/logutil"
+	"github.com/pingcap/tidb/pkg/statistics/handle/storage"
+	"github.com/pingcap/tidb/pkg/statistics/handle/util"
+	"go.uber.org/zap"
+)
+
+func (h *ddlHandlerImpl) onTruncatePartitions(t *util.DDLEvent) error {
+	globalTableInfo, addedPartInfo, droppedPartInfo := t.GetTruncatePartitionInfo()
+	// First, add the new stats meta record for the new partitions.
+	for _, def := range addedPartInfo.Definitions {
+		if err := h.statsWriter.InsertTableStats2KV(globalTableInfo, def.ID); err != nil {
+			return err
+		}
+	}
+
+	// Second, clean up the old stats meta from global stats meta for the dropped partitions.
+	// Do not forget to put those operations in one transaction.
+	if err := util.CallWithSCtx(h.statsHandler.SPool(), func(sctx sessionctx.Context) error {
+		count := int64(0)
+		partitionIDs := make([]int64, 0, len(droppedPartInfo.Definitions))
+		partitionNames := make([]string, 0, len(droppedPartInfo.Definitions))
+		for _, def := range droppedPartInfo.Definitions {
+			// Get the count and modify count of the partition.
+			tableCount, _, _, err := storage.StatsMetaCountAndModifyCount(sctx, def.ID)
+			if err != nil {
+				return err
+			}
+			count += tableCount
+			partitionIDs = append(partitionIDs, def.ID)
+			partitionNames = append(partitionNames, def.Name.O)
+		}
+
+		if count != 0 {
+			is := sctx.GetDomainInfoSchema().(infoschema.InfoSchema)
+			globalTableSchema, ok := is.SchemaByTable(globalTableInfo)
+			if !ok {
+				return errors.Errorf("schema not found for table %s", globalTableInfo.Name.O)
+			}
+			lockedTables, err := lockstats.QueryLockedTables(sctx)
+			if err != nil {
+				return errors.Trace(err)
+			}
+			isLocked := false
+			if _, ok := lockedTables[globalTableInfo.ID]; ok {
+				isLocked = true
+			}
+			startTS, err := util.GetStartTS(sctx)
+			if err != nil {
+				return errors.Trace(err)
+			}
+
+			// Because we drop the partition, we should subtract the count from the global stats.
+			// Note: We don't need to subtract the modify count from the global stats.
+			// For example:
+			// 1. The partition has 100 rows.
+			// 2. We deleted 100 rows from the partition.
+			// 3. The global stats has `count - 100 rows` and 100 modify count.
+			// 4. We drop the partition.
+			// 5. The global stats should not be `count` and 0 modify count. We need to keep the modify count.
+			delta := -count
+			err = storage.UpdateStatsMeta(
+				sctx,
+				startTS,
+				variable.TableDelta{Count: count, Delta: delta},
+				globalTableInfo.ID,
+				isLocked,
+			)
+			if err != nil {
+				fields := truncatePartitionsLogFields(
+					globalTableSchema,
+					globalTableInfo,
+					partitionIDs,
+					partitionNames,
+					count,
+					delta,
+					startTS,
+					isLocked,
+				)
+				fields = append(fields, zap.Error(err))
+				logutil.StatsLogger().Error("Update global stats after truncate partition failed",
+					fields...,
+				)
+				return err
+			}
+
+			logutil.StatsLogger().Info("Update global stats after truncate partition",
+				truncatePartitionsLogFields(
+					globalTableSchema,
+					globalTableInfo,
+					partitionIDs,
+					partitionNames,
+					count,
+					delta,
+					startTS,
+					isLocked,
+				)...,
+			)
+			return nil
+		}
+
+		return nil
+	}, util.FlagWrapTxn); err != nil {
+		return err
+	}
+
+	// Third, clean up the old stats meta from partition stats meta for the dropped partitions.
+	// It's OK to put those operations in different transactions. Because it will not affect the correctness.
+	for _, def := range droppedPartInfo.Definitions {
+		if err := h.statsWriter.ResetTableStats2KVForDrop(def.ID); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func truncatePartitionsLogFields(
+	globalTableSchema *model.DBInfo,
+	globalTableInfo *model.TableInfo,
+	partitionIDs []int64,
+	partitionNames []string,
+	count int64,
+	delta int64,
+	startTS uint64,
+	isLocked bool,
+) []zap.Field {
+	return []zap.Field{
+		zap.String("schema", globalTableSchema.Name.O),
+		zap.Int64("tableID", globalTableInfo.ID),
+		zap.String("tableName", globalTableInfo.Name.O),
+		zap.Int64s("partitionIDs", partitionIDs),
+		zap.Strings("partitionNames", partitionNames),
+		zap.Int64("count", count),
+		zap.Int64("delta", delta),
+		zap.Uint64("startTS", startTS),
+		zap.Bool("isLocked", isLocked),
+	}
+}

pkg/statistics/handle/globalstats/global_stats_test.go

@@ -598,10 +598,9 @@ func TestDDLPartition4GlobalStats(t *testing.T) {
 	require.NoError(t, h.DumpStatsDeltaToKV(true))
 	require.NoError(t, h.HandleDDLEvent(<-h.DDLEventCh()))
 	require.NoError(t, h.Update(is))
-	// The value of global.count will not be updated automatically when we truncate the table partition.
-	// Because the partition-stats in the partition table which have been truncated has not been updated.
+	// We will update the global-stats after the truncate operation.
 	globalStats = h.GetTableStats(tableInfo)
-	require.Equal(t, int64(15), globalStats.RealtimeCount)
+	require.Equal(t, int64(11), globalStats.RealtimeCount)
 
 	tk.MustExec("analyze table t;")
 	result = tk.MustQuery("show stats_meta where table_name = 't';").Rows()