planner, statistics: fix the inconsistent est when table has no stats (#52427)

pkg/planner/cardinality/BUILD.bazel

@@ -59,7 +59,7 @@ go_test(
     data = glob(["testdata/**"]),
     embed = [":cardinality"],
     flaky = True,
-    shard_count = 27,
+    shard_count = 28,
     deps = [
         "//pkg/config",
         "//pkg/domain",

pkg/planner/cardinality/selectivity_test.go

@@ -1310,3 +1310,39 @@ func TestSubsetIdxCardinality(t *testing.T) {
 		testKit.MustQuery(input[i]).Check(testkit.Rows(output[i].Result...))
 	}
 }
+
+func TestBuiltinInEstWithoutStats(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)")
+	require.NoError(t, h.HandleDDLEvent(<-h.DDLEventCh()))
+	tk.MustExec("insert into t values(1), (2), (3), (4), (5), (6), (7), (8), (9), (10)")
+	require.NoError(t, h.DumpStatsDeltaToKV(true))
+	is := dom.InfoSchema()
+	require.NoError(t, h.Update(is))
+
+	tk.MustQuery("explain format='brief' select * from t where a in (1, 2, 3, 4, 5, 6, 7, 8)").Check(testkit.Rows(
+		"TableReader 0.08 root  data:Selection",
+		"└─Selection 0.08 cop[tikv]  in(test.t.a, 1, 2, 3, 4, 5, 6, 7, 8)",
+		"  └─TableFullScan 10.00 cop[tikv] table:t keep order:false, stats:pseudo",
+	))
+
+	h.Clear()
+	require.NoError(t, h.InitStatsLite(is))
+	tk.MustQuery("explain format='brief' select * from t where a in (1, 2, 3, 4, 5, 6, 7, 8)").Check(testkit.Rows(
+		"TableReader 0.08 root  data:Selection",
+		"└─Selection 0.08 cop[tikv]  in(test.t.a, 1, 2, 3, 4, 5, 6, 7, 8)",
+		"  └─TableFullScan 10.00 cop[tikv] table:t keep order:false, stats:pseudo",
+	))
+
+	h.Clear()
+	require.NoError(t, h.InitStats(is))
+	tk.MustQuery("explain format='brief' select * from t where a in (1, 2, 3, 4, 5, 6, 7, 8)").Check(testkit.Rows(
+		"TableReader 0.08 root  data:Selection",
+		"└─Selection 0.08 cop[tikv]  in(test.t.a, 1, 2, 3, 4, 5, 6, 7, 8)",
+		"  └─TableFullScan 10.00 cop[tikv] table:t keep order:false, stats:pseudo",
+	))
+}

pkg/planner/core/collect_column_stats_usage.go

@@ -195,11 +195,21 @@ func (c *columnStatsUsageCollector) addHistNeededColumns(ds *DataSource) {
 	colIDSet := intset.NewFastIntSet()
 
 	for _, col := range columns {
+		// If the column is plan-generated one, Skip it.
+		// TODO: we may need to consider the ExtraHandle.
+		if col.ID < 0 {
+			continue
+		}
 		tblColID := model.TableItemID{TableID: ds.physicalTableID, ID: col.ID, IsIndex: false}
 		colIDSet.Insert(int(col.ID))
 		c.histNeededCols[tblColID] = true
 	}
 	for _, col := range ds.Columns {
+		// If the column is plan-generated one, Skip it.
+		// TODO: we may need to consider the ExtraHandle.
+		if col.ID < 0 {
+			continue
+		}
 		if !colIDSet.Has(int(col.ID)) && !col.Hidden {
 			tblColID := model.TableItemID{TableID: ds.physicalTableID, ID: col.ID, IsIndex: false}
 			if _, ok := c.histNeededCols[tblColID]; ok {

pkg/statistics/handle/storage/read.go

@@ -572,7 +572,9 @@ func CleanFakeItemsForShowHistInFlights(statsCache statstypes.StatsCache) int {
 		if item.IsIndex {
 			_, loadNeeded = tbl.IndexIsLoadNeeded(item.ID)
 		} else {
-			_, loadNeeded = tbl.ColumnIsLoadNeeded(item.ID, true)
+			var analyzed bool
+			_, loadNeeded, analyzed = tbl.ColumnIsLoadNeeded(item.ID, true)
+			loadNeeded = loadNeeded && analyzed
 		}
 		if !loadNeeded {
 			statistics.HistogramNeededItems.Delete(item)
@@ -589,8 +591,8 @@ func loadNeededColumnHistograms(sctx sessionctx.Context, statsCache statstypes.S
 		return nil
 	}
 	var colInfo *model.ColumnInfo
-	_, loadNeeded := tbl.ColumnIsLoadNeeded(col.ID, true)
-	if !loadNeeded {
+	_, loadNeeded, analyzed := tbl.ColumnIsLoadNeeded(col.ID, true)
+	if !loadNeeded || !analyzed {
 		statistics.HistogramNeededItems.Delete(col)
 		return nil
 	}

pkg/statistics/handle/syncload/stats_syncload.go

@@ -155,7 +155,7 @@ func (s *statsSyncLoad) removeHistLoadedColumns(neededItems []model.StatsLoadIte
 			}
 			continue
 		}
-		_, loadNeeded := tbl.ColumnIsLoadNeeded(item.ID, item.FullLoad)
+		_, loadNeeded, _ := tbl.ColumnIsLoadNeeded(item.ID, item.FullLoad)
 		if loadNeeded {
 			remainedItems = append(remainedItems, item)
 		}
@@ -270,7 +270,7 @@ func (s *statsSyncLoad) handleOneItemTask(sctx sessionctx.Context, task *statsty
 			wrapper.idxInfo = tbl.ColAndIdxExistenceMap.GetIndex(item.ID)
 		}
 	} else {
-		col, loadNeeded := tbl.ColumnIsLoadNeeded(item.ID, task.Item.FullLoad)
+		col, loadNeeded, analyzed := tbl.ColumnIsLoadNeeded(item.ID, task.Item.FullLoad)
 		if !loadNeeded {
 			return result, nil
 		}
@@ -279,6 +279,20 @@ func (s *statsSyncLoad) handleOneItemTask(sctx sessionctx.Context, task *statsty
 		} else {
 			wrapper.colInfo = tbl.ColAndIdxExistenceMap.GetCol(item.ID)
 		}
+		// If this column is not analyzed yet and we don't have it in memory.
+		// We create a fake one for the pseudo estimation.
+		if loadNeeded && !analyzed {
+			wrapper.col = &statistics.Column{
+				PhysicalID: item.TableID,
+				Info:       wrapper.colInfo,
+				Histogram:  *statistics.NewHistogram(item.ID, 0, 0, 0, &wrapper.colInfo.FieldType, 0, 0),
+				IsHandle:   tbl.IsPkIsHandle && mysql.HasPriKeyFlag(wrapper.colInfo.GetFlag()),
+			}
+			if s.updateCachedItem(item, wrapper.col, wrapper.idx, task.Item.FullLoad) {
+				return result, nil
+			}
+			return nil, nil
+		}
 	}
 	t := time.Now()
 	needUpdate := false

pkg/statistics/table.go

@@ -626,25 +626,37 @@ func (t *Table) GetStatsHealthy() (int64, bool) {
 // The Column should be visible in the table and really has analyzed statistics in the stroage.
 // Also, if the stats has been loaded into the memory, we also don't need to load it.
 // We return the Column together with the checking result, to avoid accessing the map multiple times.
-func (t *Table) ColumnIsLoadNeeded(id int64, fullLoad bool) (*Column, bool) {
+// The first bool is whether we have it in memory. The second bool is whether this column has stats in the system table or not.
+func (t *Table) ColumnIsLoadNeeded(id int64, fullLoad bool) (*Column, bool, bool) {
+	if t.Pseudo {
+		return nil, false, false
+	}
 	col, ok := t.Columns[id]
 	hasAnalyzed := t.ColAndIdxExistenceMap.HasAnalyzed(id, false)
 
-	// If it's not analyzed yet. Don't need to load it.
+	// If it's not analyzed yet.
 	if !hasAnalyzed {
-		return nil, false
+		// If we don't have it in memory, we create a fake hist for pseudo estimation (see handleOneItemTask()).
+		if !ok {
+			// If we don't have this column. We skip it.
+			// It's something ridiculous. But it's possible that the stats don't have some ColumnInfo.
+			// We need to find a way to maintain it more correctly.
+			return nil, t.ColAndIdxExistenceMap.Has(id, false), false
+		}
+		// Otherwise we don't need to load it.
+		return nil, false, false
 	}
 
 	// Restore the condition from the simplified form:
 	// 1. !ok && hasAnalyzed => need load
 	// 2. ok && hasAnalyzed && fullLoad && !col.IsFullLoad => need load
 	// 3. ok && hasAnalyzed && !fullLoad && !col.statsInitialized => need load
 	if !ok || (fullLoad && !col.IsFullLoad()) || (!fullLoad && !col.statsInitialized) {
-		return col, true
+		return col, true, true
 	}
 
 	// Otherwise don't need load it.
-	return col, false
+	return col, false, true
 }
 
 // IndexIsLoadNeeded checks whether the index needs trigger the async/sync load.