stats: fix selectivity estimation for primary key (#8134) (#8149)

pingcap · Nov 2, 2018 · cc0949d · cc0949d
1 parent f48a510
commit cc0949d
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Showing 7 changed files with 27 additions and 6 deletions.
diff --git a/statistics/bootstrap.go b/statistics/bootstrap.go
@@ -120,7 +120,7 @@ func (h *Handle) initStatsHistograms4Chunk(is infoschema.InfoSchema, tables stat
 				continue
 			}
 			hist := NewHistogram(id, ndv, nullCount, version, &colInfo.FieldType, 0, totColSize)
-			table.Columns[hist.ID] = &Column{Histogram: *hist, Info: colInfo, Count: nullCount}
+			table.Columns[hist.ID] = &Column{Histogram: *hist, Info: colInfo, Count: nullCount, isHandle: tbl.Meta().PKIsHandle && mysql.HasPriKeyFlag(colInfo.Flag)}
 		}
 	}
 }

diff --git a/statistics/dump.go b/statistics/dump.go
@@ -216,6 +216,7 @@ func TableStatsFromJSON(tableInfo *model.TableInfo, physicalID int64, jsonTbl *J
 				CMSketch:  CMSketchFromProto(jsonCol.CMSketch),
 				Info:      colInfo,
 				Count:     count,
+				isHandle:  tableInfo.PKIsHandle && mysql.HasPriKeyFlag(colInfo.Flag),
 			}
 			tbl.Columns[col.ID] = col
 		}

diff --git a/statistics/handle.go b/statistics/handle.go
@@ -258,7 +258,7 @@ func (h *Handle) LoadNeededHistograms() error {
 		if err != nil {
 			return errors.Trace(err)
 		}
-		tbl.Columns[c.ID] = &Column{Histogram: *hg, Info: c.Info, CMSketch: cms, Count: int64(hg.totalRowCount())}
+		tbl.Columns[c.ID] = &Column{Histogram: *hg, Info: c.Info, CMSketch: cms, Count: int64(hg.totalRowCount()), isHandle: c.isHandle}
 		h.UpdateTableStats([]*Table{tbl}, nil)
 		histogramNeededColumns.delete(col)
 	}

diff --git a/statistics/histogram.go b/statistics/histogram.go
@@ -720,8 +720,9 @@ func (e *ErrorRate) merge(rate *ErrorRate) {
 type Column struct {
 	Histogram
 	*CMSketch
-	Count int64
-	Info  *model.ColumnInfo
+	Count    int64
+	Info     *model.ColumnInfo
+	isHandle bool
 	ErrorRate
 }
 

diff --git a/statistics/selectivity.go b/statistics/selectivity.go
@@ -180,7 +180,7 @@ func (coll *HistColl) Selectivity(ctx sessionctx.Context, exprs []expression.Exp
 				return 0, errors.Trace(err)
 			}
 			sets = append(sets, &exprSet{tp: colType, ID: id, mask: maskCovered, ranges: ranges, numCols: 1})
-			if mysql.HasPriKeyFlag(colInfo.Info.Flag) {
+			if colInfo.isHandle {
 				sets[len(sets)-1].tp = pkType
 			}
 		}

diff --git a/statistics/selectivity_test.go b/statistics/selectivity_test.go
@@ -324,6 +324,23 @@ func (s *testSelectivitySuite) TestEstimationForUnknownValues(c *C) {
 	c.Assert(count, Equals, 0.0)
 }
 
+func (s *testSelectivitySuite) TestPrimaryKeySelectivity(c *C) {
+	testKit := testkit.NewTestKit(c, s.store)
+	testKit.MustExec("use test")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec("create table t(a char(10) primary key, b int)")
+	testKit.MustQuery(`explain select * from t where a > "t"`).Check(testkit.Rows(
+		"IndexLookUp_10 3333.33 root ",
+		"├─IndexScan_8 3333.33 cop table:t, index:a, range:(\"t\",+inf], keep order:false, stats:pseudo",
+		"└─TableScan_9 3333.33 cop table:t, keep order:false, stats:pseudo"))
+
+	testKit.MustExec("drop table t")
+	testKit.MustExec("create table t(a int primary key, b int)")
+	testKit.MustQuery(`explain select * from t where a > 1`).Check(testkit.Rows(
+		"TableReader_6 3333.33 root data:TableScan_5",
+		"└─TableScan_5 3333.33 cop table:t, range:(1,+inf], keep order:false, stats:pseudo"))
+}
+
 func BenchmarkSelectivity(b *testing.B) {
 	c := &C{}
 	s := &testSelectivitySuite{}

diff --git a/statistics/table.go b/statistics/table.go
@@ -188,6 +188,7 @@ func (h *Handle) columnStatsFromStorage(row chunk.Row, table *Table, tableInfo *
 				Info:      colInfo,
 				Count:     count + nullCount,
 				ErrorRate: errorRate,
+				isHandle:  tableInfo.PKIsHandle && mysql.HasPriKeyFlag(colInfo.Flag),
 			}
 			break
 		}
@@ -206,6 +207,7 @@ func (h *Handle) columnStatsFromStorage(row chunk.Row, table *Table, tableInfo *
 				CMSketch:  cms,
 				Count:     int64(hg.totalRowCount()),
 				ErrorRate: errorRate,
+				isHandle:  tableInfo.PKIsHandle && mysql.HasPriKeyFlag(colInfo.Flag),
 			}
 			break
 		}
@@ -610,7 +612,7 @@ func PseudoTable(tblInfo *model.TableInfo) *Table {
 	}
 	for _, col := range tblInfo.Columns {
 		if col.State == model.StatePublic {
-			t.Columns[col.ID] = &Column{Info: col}
+			t.Columns[col.ID] = &Column{Info: col, isHandle: tblInfo.PKIsHandle && mysql.HasPriKeyFlag(col.Flag)}
 		}
 	}
 	for _, idx := range tblInfo.Indices {