statistics: change the upper bound of the out-of-range estimation to modify count | tidb-test=pr/2012

statistics/column.go

@@ -184,7 +184,7 @@ func (c *Column) equalRowCount(sctx sessionctx.Context, val types.Datum, encoded
 }
 
 // GetColumnRowCount estimates the row count by a slice of Range.
-func (c *Column) GetColumnRowCount(sctx sessionctx.Context, ranges []*ranger.Range, realtimeRowCount int64, pkIsHandle bool) (float64, error) {
+func (c *Column) GetColumnRowCount(sctx sessionctx.Context, ranges []*ranger.Range, realtimeRowCount, modifyCount int64, pkIsHandle bool) (float64, error) {
 	sc := sctx.GetSessionVars().StmtCtx
 	var rowCount float64
 	for _, rg := range ranges {
@@ -281,11 +281,7 @@ func (c *Column) GetColumnRowCount(sctx sessionctx.Context, ranges []*ranger.Ran
 
 		// handling the out-of-range part
 		if (c.outOfRange(lowVal) && !lowVal.IsNull()) || c.outOfRange(highVal) {
-			increaseCount := realtimeRowCount - int64(c.TotalRowCount())
-			if increaseCount < 0 {
-				increaseCount = 0
-			}
-			cnt += c.Histogram.outOfRangeRowCount(&lowVal, &highVal, increaseCount)
+			cnt += c.Histogram.outOfRangeRowCount(&lowVal, &highVal, modifyCount)
 		}
 
 		rowCount += cnt

statistics/handle/update.go

@@ -1474,10 +1474,10 @@ func (h *Handle) RecalculateExpectCount(q *statistics.QueryFeedback, enablePseud
 	expected := 0.0
 	if isIndex {
 		idx := t.Indices[id]
-		expected, err = idx.GetRowCount(sctx, nil, ranges, t.Count)
+		expected, err = idx.GetRowCount(sctx, nil, ranges, t.Count, t.ModifyCount)
 	} else {
 		c := t.Columns[id]
-		expected, err = c.GetColumnRowCount(sctx, ranges, t.Count, true)
+		expected, err = c.GetColumnRowCount(sctx, ranges, t.Count, t.ModifyCount, true)
 	}
 	q.Expected = int64(expected)
 	return err

statistics/histogram.go

@@ -778,7 +778,7 @@ func (hg *Histogram) outOfRange(val types.Datum) bool {
 
 // outOfRangeRowCount estimate the row count of part of [lDatum, rDatum] which is out of range of the histogram.
 // Here we assume the density of data is decreasing from the lower/upper bound of the histogram toward outside.
-// The maximum row count it can get is the increaseCount. It reaches the maximum when out-of-range width reaches histogram range width.
+// The maximum row count it can get is the modifyCount. It reaches the maximum when out-of-range width reaches histogram range width.
 // As it shows below. To calculate the out-of-range row count, we need to calculate the percentage of the shaded area.
 // Note that we assume histL-boundL == histR-histL == boundR-histR here.
 /*
@@ -795,7 +795,7 @@ func (hg *Histogram) outOfRange(val types.Datum) bool {
          │   │
     lDatum  rDatum
 */
-func (hg *Histogram) outOfRangeRowCount(lDatum, rDatum *types.Datum, increaseCount int64) float64 {
+func (hg *Histogram) outOfRangeRowCount(lDatum, rDatum *types.Datum, modifyCount int64) float64 {
 	if hg.Len() == 0 {
 		return 0
 	}
@@ -879,8 +879,14 @@ func (hg *Histogram) outOfRangeRowCount(lDatum, rDatum *types.Datum, increaseCou
 		totalPercent = 1
 	}
 	rowCount := totalPercent * hg.notNullCount()
-	if rowCount > float64(increaseCount) {
-		return float64(increaseCount)
+
+	// Use the modifyCount as the upper bound. Note that modifyCount contains insert, delete and update. So this is
+	// a rather loose upper bound.
+	// There are some scenarios where we need to handle out-of-range estimation after both insert and delete happen.
+	// But we don't know how many increases are in the modifyCount. So we have to use this loose bound to ensure it
+	// can produce a reasonable results in this scenario.
+	if rowCount > float64(modifyCount) {
+		return float64(modifyCount)
 	}
 	return rowCount
 }

statistics/index.go

@@ -216,7 +216,7 @@ func (idx *Index) QueryBytes(d []byte) uint64 {
 
 // GetRowCount returns the row count of the given ranges.
 // It uses the modifyCount to adjust the influence of modifications on the table.
-func (idx *Index) GetRowCount(sctx sessionctx.Context, coll *HistColl, indexRanges []*ranger.Range, realtimeRowCount int64) (float64, error) {
+func (idx *Index) GetRowCount(sctx sessionctx.Context, coll *HistColl, indexRanges []*ranger.Range, realtimeRowCount, modifyCount int64) (float64, error) {
 	idx.checkStats()
 	sc := sctx.GetSessionVars().StmtCtx
 	totalCount := float64(0)
@@ -309,11 +309,7 @@ func (idx *Index) GetRowCount(sctx sessionctx.Context, coll *HistColl, indexRang
 
 		// handling the out-of-range part
 		if (idx.outOfRange(l) && !(isSingleCol && lowIsNull)) || idx.outOfRange(r) {
-			increaseCount := realtimeRowCount - int64(idx.TotalRowCount())
-			if increaseCount < 0 {
-				increaseCount = 0
-			}
-			totalCount += idx.Histogram.outOfRangeRowCount(&l, &r, increaseCount)
+			totalCount += idx.Histogram.outOfRangeRowCount(&l, &r, modifyCount)
 		}
 	}
 	totalCount = mathutil.Clamp(totalCount, 0, float64(realtimeRowCount))

statistics/selectivity_test.go

@@ -127,7 +127,7 @@ func TestOutOfRangeEstimation(t *testing.T) {
 	statsTbl := h.GetTableStats(table.Meta())
 	sctx := mock.NewContext()
 	col := statsTbl.Columns[table.Meta().Columns[0].ID]
-	count, err := col.GetColumnRowCount(sctx, getRange(900, 900), statsTbl.Count, false)
+	count, err := col.GetColumnRowCount(sctx, getRange(900, 900), statsTbl.Count, statsTbl.ModifyCount, false)
 	require.NoError(t, err)
 	// Because the ANALYZE collect data by random sampling, so the result is not an accurate value.
 	// so we use a range here.
@@ -146,8 +146,9 @@ func TestOutOfRangeEstimation(t *testing.T) {
 	statsSuiteData := statistics.GetStatsSuiteData()
 	statsSuiteData.LoadTestCases(t, &input, &output)
 	increasedTblRowCount := int64(float64(statsTbl.Count) * 1.5)
+	modifyCount := int64(float64(statsTbl.Count) * 0.5)
 	for i, ran := range input {
-		count, err = col.GetColumnRowCount(sctx, getRange(ran.Start, ran.End), increasedTblRowCount, false)
+		count, err = col.GetColumnRowCount(sctx, getRange(ran.Start, ran.End), increasedTblRowCount, modifyCount, false)
 		require.NoError(t, err)
 		testdata.OnRecord(func() {
 			output[i].Start = ran.Start
@@ -159,6 +160,42 @@ func TestOutOfRangeEstimation(t *testing.T) {
 	}
 }
 
+// TestOutOfRangeEstimationAfterDelete tests the out-of-range estimation after deletion happen.
+// The test result doesn't perfectly reflect the actual data distribution, but this is the expected behavior for now.
+func TestOutOfRangeEstimationAfterDelete(t *testing.T) {
+	store, dom := testkit.CreateMockStoreAndDomain(t)
+	testKit := testkit.NewTestKit(t, store)
+	h := dom.StatsHandle()
+	testKit.MustExec("use test")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec("create table t(a int unsigned)")
+	require.NoError(t, h.HandleDDLEvent(<-h.DDLEventCh()))
+	for i := 0; i < 3000; i++ {
+		testKit.MustExec(fmt.Sprintf("insert into t values (%v)", i/5+300)) // [300, 900)
+	}
+	require.Nil(t, h.DumpStatsDeltaToKV(handle.DumpAll))
+	testKit.MustExec("analyze table t with 1 samplerate, 0 topn")
+	testKit.MustExec("delete from t where a < 500")
+	require.Nil(t, h.DumpStatsDeltaToKV(handle.DumpAll))
+	require.Nil(t, h.Update(dom.InfoSchema()))
+	var (
+		input  []string
+		output []struct {
+			SQL    string
+			Result []string
+		}
+	)
+	statsSuiteData := statistics.GetStatsSuiteData()
+	statsSuiteData.LoadTestCases(t, &input, &output)
+	for i := range input {
+		testdata.OnRecord(func() {
+			output[i].SQL = input[i]
+			output[i].Result = testdata.ConvertRowsToStrings(testKit.MustQuery(input[i]).Rows())
+		})
+		testKit.MustQuery(input[i]).Check(testkit.Rows(output[i].Result...))
+	}
+}
+
 func TestEstimationForUnknownValues(t *testing.T) {
 	store, dom := testkit.CreateMockStoreAndDomain(t)
 	testKit := testkit.NewTestKit(t, store)
@@ -543,6 +580,7 @@ func TestSelectivity(t *testing.T) {
 		require.Truef(t, math.Abs(ratio-tt.selectivity) < eps, "for %s, needed: %v, got: %v", tt.exprs, tt.selectivity, ratio)
 
 		histColl.Count *= 10
+		histColl.ModifyCount = histColl.Count * 9
 		ratio, _, err = histColl.Selectivity(sctx, sel.Conditions, nil)
 		require.NoErrorf(t, err, "for %s", tt.exprs)
 		require.Truef(t, math.Abs(ratio-tt.selectivityAfterIncrease) < eps, "for %s, needed: %v, got: %v", tt.exprs, tt.selectivityAfterIncrease, ratio)
@@ -748,7 +786,7 @@ func TestSmallRangeEstimation(t *testing.T) {
 	statsSuiteData := statistics.GetStatsSuiteData()
 	statsSuiteData.LoadTestCases(t, &input, &output)
 	for i, ran := range input {
-		count, err := col.GetColumnRowCount(sctx, getRange(ran.Start, ran.End), statsTbl.Count, false)
+		count, err := col.GetColumnRowCount(sctx, getRange(ran.Start, ran.End), statsTbl.Count, statsTbl.ModifyCount, false)
 		require.NoError(t, err)
 		testdata.OnRecord(func() {
 			output[i].Start = ran.Start
@@ -991,3 +1029,49 @@ type outputType struct {
 	SQL    string
 	Result []string
 }
+
+func TestGlobalStatsOutOfRangeEstimationAfterDelete(t *testing.T) {
+	store, dom := testkit.CreateMockStoreAndDomain(t)
+	testKit := testkit.NewTestKit(t, store)
+	h := dom.StatsHandle()
+	testKit.MustExec("use test")
+	testKit.MustExec("set @@tidb_partition_prune_mode='dynamic'")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec("create table t(a int unsigned) " +
+		"partition by range (a) " +
+		"(partition p0 values less than (400), " +
+		"partition p1 values less than (600), " +
+		"partition p2 values less than (800)," +
+		"partition p3 values less than (1000)," +
+		"partition p4 values less than (1200))")
+	require.NoError(t, h.HandleDDLEvent(<-h.DDLEventCh()))
+	for i := 0; i < 3000; i++ {
+		testKit.MustExec(fmt.Sprintf("insert into t values (%v)", i/5+300)) // [300, 900)
+	}
+	require.Nil(t, h.DumpStatsDeltaToKV(handle.DumpAll))
+	testKit.MustExec("analyze table t with 1 samplerate, 0 topn")
+	testKit.MustExec("delete from t where a < 500")
+	require.Nil(t, h.DumpStatsDeltaToKV(handle.DumpAll))
+	require.Nil(t, h.Update(dom.InfoSchema()))
+	var (
+		input  []string
+		output []struct {
+			SQL    string
+			Result []string
+		}
+	)
+	statsSuiteData := statistics.GetStatsSuiteData()
+	statsSuiteData.LoadTestCases(t, &input, &output)
+	for i := range input {
+		testdata.OnRecord(func() {
+			output[i].SQL = input[i]
+			output[i].Result = testdata.ConvertRowsToStrings(testKit.MustQuery(input[i]).Rows())
+		})
+		testKit.MustQuery(input[i]).Check(testkit.Rows(output[i].Result...))
+	}
+	testKit.MustExec("analyze table t partition p4 with 1 samplerate, 0 topn")
+	require.Nil(t, h.Update(dom.InfoSchema()))
+	for i := range input {
+		testKit.MustQuery(input[i]).Check(testkit.Rows(output[i].Result...))
+	}
+}

statistics/table.go

@@ -566,7 +566,7 @@ func (coll *HistColl) GetRowCountByIntColumnRanges(sctx sessionctx.Context, colI
 		}
 		return result, nil
 	}
-	result, err = c.GetColumnRowCount(sctx, intRanges, coll.Count, true)
+	result, err = c.GetColumnRowCount(sctx, intRanges, coll.Count, coll.ModifyCount, true)
 	if sc.EnableOptimizerCETrace {
 		CETraceRange(sctx, coll.PhysicalID, []string{c.Info.Name.O}, intRanges, "Column Stats", uint64(result))
 	}
@@ -587,7 +587,7 @@ func (coll *HistColl) GetRowCountByColumnRanges(sctx sessionctx.Context, colID i
 		}
 		return result, err
 	}
-	result, err := c.GetColumnRowCount(sctx, colRanges, coll.Count, false)
+	result, err := c.GetColumnRowCount(sctx, colRanges, coll.Count, coll.ModifyCount, false)
 	if sc.EnableOptimizerCETrace {
 		CETraceRange(sctx, coll.PhysicalID, []string{c.Info.Name.O}, colRanges, "Column Stats", uint64(result))
 	}
@@ -623,7 +623,7 @@ func (coll *HistColl) GetRowCountByIndexRanges(sctx sessionctx.Context, idxID in
 	if idx.CMSketch != nil && idx.StatsVer == Version1 {
 		result, err = coll.getIndexRowCount(sctx, idxID, indexRanges)
 	} else {
-		result, err = idx.GetRowCount(sctx, coll, indexRanges, coll.Count)
+		result, err = idx.GetRowCount(sctx, coll, indexRanges, coll.Count, coll.ModifyCount)
 	}
 	if sc.EnableOptimizerCETrace {
 		CETraceRange(sctx, coll.PhysicalID, colNames, indexRanges, "Index Stats", uint64(result))
@@ -959,7 +959,7 @@ func (coll *HistColl) crossValidationSelectivity(sctx sessionctx.Context, idx *I
 				Collators:   []collate.Collator{idxPointRange.Collators[i]},
 			}
 
-			rowCount, err := col.GetColumnRowCount(sctx, []*ranger.Range{&rang}, coll.Count, col.IsHandle)
+			rowCount, err := col.GetColumnRowCount(sctx, []*ranger.Range{&rang}, coll.Count, coll.ModifyCount, col.IsHandle)
 			if err != nil {
 				return 0, 0, err
 			}
@@ -1031,7 +1031,7 @@ func (coll *HistColl) getIndexRowCount(sctx sessionctx.Context, idxID int64, ind
 		// on single-column index, use previous way as well, because CMSketch does not contain null
 		// values in this case.
 		if rangePosition == 0 || isSingleColIdxNullRange(idx, ran) {
-			count, err := idx.GetRowCount(sctx, nil, []*ranger.Range{ran}, coll.Count)
+			count, err := idx.GetRowCount(sctx, nil, []*ranger.Range{ran}, coll.Count, coll.ModifyCount)
 			if err != nil {
 				return 0, errors.Trace(err)
 			}

statistics/testdata/stats_suite_in.json

@@ -259,5 +259,41 @@
         "End": 0
       }
     ]
+  },
+  {
+    "name": "TestOutOfRangeEstimationAfterDelete",
+    "cases": [
+      "explain format = 'brief' select * from t where a <= 300",
+      "explain format = 'brief' select * from t where a < 300",
+      "explain format = 'brief' select * from t where a <= 500",
+      "explain format = 'brief' select * from t where a >= 300 and a <= 900",
+      "explain format = 'brief' select * from t where a >= 900",
+      "explain format = 'brief' select * from t where a > 900",
+      "explain format = 'brief' select * from t where a >= 300",
+      "explain format = 'brief' select * from t where a <= 900",
+      "explain format = 'brief' select * from t where a > 800 and a < 1000",
+      "explain format = 'brief' select * from t where a > 900 and a < 1000",
+      "explain format = 'brief' select * from t where a > 900 and a < 1100",
+      "explain format = 'brief' select * from t where a > 200 and a < 300",
+      "explain format = 'brief' select * from t where a > 100 and a < 300"
+    ]
+  },
+  {
+    "name": "TestGlobalStatsOutOfRangeEstimationAfterDelete",
+    "cases": [
+      "explain format = 'brief' select * from t where a <= 300",
+      "explain format = 'brief' select * from t where a < 300",
+      "explain format = 'brief' select * from t where a <= 500",
+      "explain format = 'brief' select * from t where a >= 300 and a <= 900",
+      "explain format = 'brief' select * from t where a >= 900",
+      "explain format = 'brief' select * from t where a > 900",
+      "explain format = 'brief' select * from t where a >= 300",
+      "explain format = 'brief' select * from t where a <= 900",
+      "explain format = 'brief' select * from t where a > 800 and a < 1000",
+      "explain format = 'brief' select * from t where a > 900 and a < 1000",
+      "explain format = 'brief' select * from t where a > 900 and a < 1100",
+      "explain format = 'brief' select * from t where a > 200 and a < 300",
+      "explain format = 'brief' select * from t where a > 100 and a < 300"
+    ]
   }
 ]