From 735e1717ca8edded2507222931eedb63546d4d56 Mon Sep 17 00:00:00 2001
From: xuyifan <675434007@qq.com>
Date: Thu, 9 Mar 2023 20:02:13 +0800
Subject: [PATCH 1/2] fix unnecessary index fmsketch loading

---
 statistics/integration_test.go      | 24 ++++++++++++++++++++++++
 statistics/interact_with_storage.go | 15 ++++++++++-----
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/statistics/integration_test.go b/statistics/integration_test.go
index 1c8672b790ffd..4f2c87fdd09f5 100644
--- a/statistics/integration_test.go
+++ b/statistics/integration_test.go
@@ -693,3 +693,27 @@ func TestSingleColumnIndexNDV(t *testing.T) {
 		require.Equal(t, expectedResults[i][2], row[7]) // null_count
 	}
 }
+
+func TestUpdateNotLoadIndexFMSketch(t *testing.T) {
+	store, dom := testkit.CreateMockStoreAndDomain(t)
+	tk := testkit.NewTestKit(t, store)
+	h := dom.StatsHandle()
+	tk.MustExec("use test")
+	tk.MustExec("create table t(a int, b int, index idx(a)) partition by range (a) (partition p0 values less than (10),partition p1 values less than maxvalue)")
+	tk.MustExec("insert into t values (1,2), (3,4), (5,6), (7,8)")
+	require.NoError(t, h.HandleDDLEvent(<-h.DDLEventCh()))
+	tk.MustExec("analyze table t")
+	is := dom.InfoSchema()
+	tbl, err := is.TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
+	require.NoError(t, err)
+	tblInfo := tbl.Meta()
+	idxInfo := tblInfo.Indices[0]
+	p0 := tblInfo.Partition.Definitions[0]
+	p1 := tblInfo.Partition.Definitions[1]
+	require.Nil(t, h.GetPartitionStats(tblInfo, p0.ID).Indices[idxInfo.ID].FMSketch)
+	require.Nil(t, h.GetPartitionStats(tblInfo, p1.ID).Indices[idxInfo.ID].FMSketch)
+	h.Clear()
+	require.NoError(t, h.Update(is))
+	require.Nil(t, h.GetPartitionStats(tblInfo, p0.ID).Indices[idxInfo.ID].FMSketch)
+	require.Nil(t, h.GetPartitionStats(tblInfo, p1.ID).Indices[idxInfo.ID].FMSketch)
+}
diff --git a/statistics/interact_with_storage.go b/statistics/interact_with_storage.go
index c0acce31b77b7..ba7f6f78cb78c 100644
--- a/statistics/interact_with_storage.go
+++ b/statistics/interact_with_storage.go
@@ -253,7 +253,7 @@ func ExtendedStatsFromStorage(reader *StatsReader, table *Table, physicalID int6
 	return table, nil
 }
 
-func indexStatsFromStorage(reader *StatsReader, row chunk.Row, table *Table, tableInfo *model.TableInfo) error {
+func indexStatsFromStorage(reader *StatsReader, row chunk.Row, table *Table, tableInfo *model.TableInfo, loadAll bool) error {
 	histID := row.GetInt64(2)
 	distinct := row.GetInt64(3)
 	histVer := row.GetUint64(4)
@@ -279,9 +279,14 @@ func indexStatsFromStorage(reader *StatsReader, row chunk.Row, table *Table, tab
 			if err != nil {
 				return errors.Trace(err)
 			}
-			fmSketch, err := FMSketchFromStorage(reader, table.PhysicalID, 1, histID)
-			if err != nil {
-				return errors.Trace(err)
+			var fmSketch *FMSketch
+			if loadAll {
+				// FMSketch is only used when merging partition stats into global stats. When merging partition stats into global stats,
+				// we load all the statistics, i.e., loadAll is true.
+				fmSketch, err = FMSketchFromStorage(reader, table.PhysicalID, 1, histID)
+				if err != nil {
+					return errors.Trace(err)
+				}
 			}
 			idx = &Index{
 				Histogram:  *hg,
@@ -454,7 +459,7 @@ func TableStatsFromStorage(reader *StatsReader, tableInfo *model.TableInfo, phys
 	}
 	for _, row := range rows {
 		if row.GetInt64(1) > 0 {
-			err = indexStatsFromStorage(reader, row, table, tableInfo)
+			err = indexStatsFromStorage(reader, row, table, tableInfo, loadAll)
 		} else {
 			err = columnStatsFromStorage(reader, row, table, tableInfo, loadAll, lease)
 		}

From cf420a2e9e4c4b753f6bd5e6fa909ec091e90750 Mon Sep 17 00:00:00 2001
From: xuyifan <675434007@qq.com>
Date: Fri, 10 Mar 2023 15:02:56 +0800
Subject: [PATCH 2/2] fmt

---
 statistics/integration_test.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/statistics/integration_test.go b/statistics/integration_test.go
index e5bf21776f47e..a7563a6b06542 100644
--- a/statistics/integration_test.go
+++ b/statistics/integration_test.go
@@ -743,4 +743,3 @@ func TestUpdateNotLoadIndexFMSketch(t *testing.T) {
 	require.Nil(t, h.GetPartitionStats(tblInfo, p0.ID).Indices[idxInfo.ID].FMSketch)
 	require.Nil(t, h.GetPartitionStats(tblInfo, p1.ID).Indices[idxInfo.ID].FMSketch)
 }
-