statistics: fix wrong point range in crossValidationSelectivity (#33357)

ref pingcap/tidb#28030

statistics/integration_test.go

@@ -625,3 +625,22 @@ func TestNotLoadedStatsOnAllNULLCol(t *testing.T) {
 		"  └─TableReader(Probe) 4.00 root  data:TableFullScan",
 		"    └─TableFullScan 4.00 cop[tikv] table:t1 keep order:false"))
 }
+
+func TestCrossValidationSelectivity(t *testing.T) {
+	store, dom, clean := testkit.CreateMockStoreAndDomain(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	h := dom.StatsHandle()
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("set @@tidb_analyze_version = 1")
+	tk.MustExec("create table t (a int, b int, c int, primary key (a, b) clustered)")
+	require.NoError(t, h.HandleDDLEvent(<-h.DDLEventCh()))
+	tk.MustExec("insert into t values (1,2,3), (1,4,5)")
+	require.NoError(t, h.DumpStatsDeltaToKV(handle.DumpAll))
+	tk.MustExec("analyze table t")
+	tk.MustQuery("explain format = 'brief' select * from t where a = 1 and b > 0 and b < 1000 and c > 1000").Check(testkit.Rows(
+		"TableReader 0.00 root  data:Selection",
+		"└─Selection 0.00 cop[tikv]  gt(test.t.c, 1000)",
+		"  └─TableRangeScan 2.00 cop[tikv] table:t range:(1 0,1 1000), keep order:false"))
+}

statistics/table.go

@@ -591,23 +591,13 @@ func (coll *HistColl) crossValidationSelectivity(sctx sessionctx.Context, idx *I
 			if col.IsInvalid(sctx, coll.Pseudo) {
 				continue
 			}
-			lowExclude := idxPointRange.LowExclude
-			highExclude := idxPointRange.HighExclude
-			// Consider this case:
-			// create table t(a int, b int, c int, primary key(a,b,c));
-			// insert into t values(1,1,1),(2,2,3);
-			// explain select * from t where (a,b) in ((1,1),(2,2)) and c > 2;
-			// For column a, we will get range: (1, 1], (2, 2], but GetColumnRowCount() with rang = (2, 2] will return 0.
-			// And the result of the explain statement will output estRow 0.0. So we change it to [2, 2].
-			if lowExclude != highExclude && i < usedColsLen {
-				lowExclude = false
-				highExclude = false
-			}
+			// Since the column range is point range(LowVal is equal to HighVal), we need to set both LowExclude and HighExclude to false.
+			// Otherwise we would get 0.0 estRow from GetColumnRowCount.
 			rang := ranger.Range{
 				LowVal:      []types.Datum{idxPointRange.LowVal[i]},
-				LowExclude:  lowExclude,
+				LowExclude:  false,
 				HighVal:     []types.Datum{idxPointRange.HighVal[i]},
-				HighExclude: highExclude,
+				HighExclude: false,
 				Collators:   []collate.Collator{idxPointRange.Collators[i]},
 			}