statistics: add more tests to check accurateness of global-stats (#22948

)

statistics/fmsketch.go

@@ -170,6 +170,7 @@ func DecodeFMSketch(data []byte) (*FMSketch, error) {
 		return nil, errors.Trace(err)
 	}
 	fm := FMSketchFromProto(p)
+	fm.maxSize = 10000 // TODO: add this attribute to PB and persist it instead of using a fixed number(executor.maxSketchSize)
 	return fm, nil
 }
 

statistics/handle/handle.go

@@ -821,7 +821,15 @@ func (h *Handle) TableStatsFromStorage(tableInfo *model.TableInfo, physicalID in
 		table = table.Copy()
 	}
 	table.Pseudo = false
-	rows, _, err := reader.read("select table_id, is_index, hist_id, distinct_count, version, null_count, tot_col_size, stats_ver, flag, correlation, last_analyze_pos from mysql.stats_histograms where table_id = %?", physicalID)
+
+	rows, _, err := reader.read("select modify_count, count from mysql.stats_meta where table_id = %?", physicalID)
+	if err != nil || len(rows) == 0 {
+		return nil, err
+	}
+	table.ModifyCount = rows[0].GetInt64(0)
+	table.Count = rows[0].GetInt64(1)
+
+	rows, _, err = reader.read("select table_id, is_index, hist_id, distinct_count, version, null_count, tot_col_size, stats_ver, flag, correlation, last_analyze_pos from mysql.stats_histograms where table_id = %?", physicalID)
 	// Check deleted table.
 	if err != nil || len(rows) == 0 {
 		return nil, nil

statistics/handle/handle_test.go

@@ -762,6 +762,42 @@ func (s *testStatsSuite) TestBuildGlobalLevelStats(c *C) {
 	c.Assert(len(result.Rows()), Equals, 20)
 }
 
+func (s *testStatsSuite) TestGlobalStatsData(c *C) {
+	defer cleanEnv(c, s.store, s.do)
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec(`
+create table t (
+	a int,
+	key(a)
+)
+partition by range (a) (
+	partition p0 values less than (10),
+	partition p1 values less than (20)
+)`)
+	tk.MustExec("set @@tidb_partition_prune_mode='dynamic-only'")
+	tk.MustExec("insert into t values (1), (5), (null), (11), (15)")
+	c.Assert(s.do.StatsHandle().DumpStatsDeltaToKV(handle.DumpAll), IsNil)
+	tk.MustExec("analyze table t")
+
+	tk.MustQuery("select modify_count, count from mysql.stats_meta order by table_id asc").Check(
+		testkit.Rows("0 5", "0 3", "0 2")) // global row-count = sum(partition row-count)
+
+	// distinct, null_count, tot_col_size should be the sum of their values in partition-stats, and correlation should be 0
+	tk.MustQuery("select distinct_count, null_count, tot_col_size, correlation from mysql.stats_histograms where is_index=0 order by table_id asc").Check(
+		testkit.Rows("4 1 4 0", "2 1 2 1", "2 0 2 1"))
+
+	tk.MustQuery("show stats_buckets where is_index=0").Check(
+		testkit.Rows("test t global a 0 0 2 1 1 5 0", "test t global a 0 1 4 1 5 15 0",
+			"test t p0 a 0 0 1 1 1 1 0", "test t p0 a 0 1 2 1 5 5 0",
+			"test t p1 a 0 0 1 1 11 11 0", "test t p1 a 0 1 2 1 15 15 0"))
+	tk.MustQuery("show stats_buckets where is_index=1").Check(
+		testkit.Rows("test t global a 1 0 2 1 1 5 0", "test t global a 1 1 4 1 5 15 0",
+			"test t p0 a 1 0 1 1 1 1 0", "test t p0 a 1 1 2 1 5 5 0",
+			"test t p1 a 1 0 1 1 11 11 0", "test t p1 a 1 1 2 1 15 15 0"))
+}
+
 func (s *testStatsSuite) TestExtendedStatsDefaultSwitch(c *C) {
 	defer cleanEnv(c, s.store, s.do)
 	tk := testkit.NewTestKit(c, s.store)