stats: remove the lower bound of auto analyze ratio

sessionctx/variable/varsutil.go

@@ -537,6 +537,12 @@ func ValidateSetSystemVar(vars *SessionVars, name string, value string) (string,
 			return "", err
 		}
 		return v, nil
+	case TiDBAutoAnalyzeRatio:
+		v, err := strconv.ParseFloat(value, 64)
+		if err != nil || v < 0 {
+			return value, ErrWrongValueForVar.GenWithStackByArgs(name, value)
+		}
+		return value, nil
 	case TxnIsolation, TransactionIsolation:
 		upVal := strings.ToUpper(value)
 		_, exists := TxIsolationNames[upVal]

statistics/handle/update.go

@@ -636,13 +636,9 @@ func NeedAnalyzeTable(tbl *statistics.Table, limit time.Duration, autoAnalyzeRat
 		return false, ""
 	}
 	// Tests if current time is within the time period.
-	return timeutil.WithinDayTimePeriod(start, end, now), fmt.Sprintf("too many modifications(%v/%v)", tbl.ModifyCount, tbl.Count)
+	return timeutil.WithinDayTimePeriod(start, end, now), fmt.Sprintf("too many modifications(%v/%v>%v)", tbl.ModifyCount, tbl.Count, autoAnalyzeRatio)
 }
 
-const (
-	minAutoAnalyzeRatio = 0.3
-)
-
 func (h *Handle) getAutoAnalyzeParameters() map[string]string {
 	sql := fmt.Sprintf("select variable_name, variable_value from mysql.global_variables where variable_name in ('%s', '%s', '%s')",
 		variable.TiDBAutoAnalyzeRatio, variable.TiDBAutoAnalyzeStartTime, variable.TiDBAutoAnalyzeEndTime)
@@ -662,10 +658,7 @@ func parseAutoAnalyzeRatio(ratio string) float64 {
 	if err != nil {
 		return variable.DefAutoAnalyzeRatio
 	}
-	if autoAnalyzeRatio > 0 {
-		autoAnalyzeRatio = math.Max(autoAnalyzeRatio, minAutoAnalyzeRatio)
-	}
-	return autoAnalyzeRatio
+	return math.Max(autoAnalyzeRatio, 0)
 }
 
 func parseAnalyzePeriod(start, end string) (time.Time, time.Time, error) {

statistics/handle/update_test.go

@@ -375,7 +375,7 @@ func (s *testStatsSuite) TestAutoUpdate(c *C) {
 	testKit.MustExec("create table t (a varchar(20))")
 
 	handle.AutoAnalyzeMinCnt = 0
-	testKit.MustExec("set global tidb_auto_analyze_ratio = 0.6")
+	testKit.MustExec("set global tidb_auto_analyze_ratio = 0.2")
 	defer func() {
 		handle.AutoAnalyzeMinCnt = 1000
 		testKit.MustExec("set global tidb_auto_analyze_ratio = 0.0")
@@ -393,18 +393,18 @@ func (s *testStatsSuite) TestAutoUpdate(c *C) {
 	stats := h.GetTableStats(tableInfo)
 	c.Assert(stats.Count, Equals, int64(0))
 
-	_, err = testKit.Exec("insert into t values ('ss')")
+	_, err = testKit.Exec("insert into t values ('ss'), ('ss'), ('ss'), ('ss'), ('ss')")
 	c.Assert(err, IsNil)
 	c.Assert(h.DumpStatsDeltaToKV(handle.DumpAll), IsNil)
 	c.Assert(h.Update(is), IsNil)
 	h.HandleAutoAnalyze(is)
 	c.Assert(h.Update(is), IsNil)
 	stats = h.GetTableStats(tableInfo)
-	c.Assert(stats.Count, Equals, int64(1))
+	c.Assert(stats.Count, Equals, int64(5))
 	c.Assert(stats.ModifyCount, Equals, int64(0))
 	for _, item := range stats.Columns {
-		// TotColSize = 2(length of 'ss') + 1(size of len byte).
-		c.Assert(item.TotColSize, Equals, int64(3))
+		// TotColSize = 5*(2(length of 'ss') + 1(size of len byte)).
+		c.Assert(item.TotColSize, Equals, int64(15))
 		break
 	}
 
@@ -418,7 +418,7 @@ func (s *testStatsSuite) TestAutoUpdate(c *C) {
 	h.HandleAutoAnalyze(is)
 	c.Assert(h.Update(is), IsNil)
 	stats = h.GetTableStats(tableInfo)
-	c.Assert(stats.Count, Equals, int64(2))
+	c.Assert(stats.Count, Equals, int64(6))
 	c.Assert(stats.ModifyCount, Equals, int64(1))
 
 	_, err = testKit.Exec("insert into t values ('fff')")
@@ -428,7 +428,7 @@ func (s *testStatsSuite) TestAutoUpdate(c *C) {
 	h.HandleAutoAnalyze(is)
 	c.Assert(h.Update(is), IsNil)
 	stats = h.GetTableStats(tableInfo)
-	c.Assert(stats.Count, Equals, int64(3))
+	c.Assert(stats.Count, Equals, int64(7))
 	c.Assert(stats.ModifyCount, Equals, int64(0))
 
 	_, err = testKit.Exec("insert into t values ('eee')")
@@ -438,12 +438,12 @@ func (s *testStatsSuite) TestAutoUpdate(c *C) {
 	h.HandleAutoAnalyze(is)
 	c.Assert(h.Update(is), IsNil)
 	stats = h.GetTableStats(tableInfo)
-	c.Assert(stats.Count, Equals, int64(4))
+	c.Assert(stats.Count, Equals, int64(8))
 	// Modify count is non-zero means that we do not analyze the table.
 	c.Assert(stats.ModifyCount, Equals, int64(1))
 	for _, item := range stats.Columns {
-		// TotColSize = 6, because the table has not been analyzed, and insert statement will add 3(length of 'eee') to TotColSize.
-		c.Assert(item.TotColSize, Equals, int64(15))
+		// TotColSize = 27, because the table has not been analyzed, and insert statement will add 3(length of 'eee') to TotColSize.
+		c.Assert(item.TotColSize, Equals, int64(27))
 		break
 	}
 
@@ -457,7 +457,7 @@ func (s *testStatsSuite) TestAutoUpdate(c *C) {
 	h.HandleAutoAnalyze(is)
 	c.Assert(h.Update(is), IsNil)
 	stats = h.GetTableStats(tableInfo)
-	c.Assert(stats.Count, Equals, int64(4))
+	c.Assert(stats.Count, Equals, int64(8))
 	c.Assert(stats.ModifyCount, Equals, int64(0))
 	hg, ok := stats.Indices[tableInfo.Indices[0].ID]
 	c.Assert(ok, IsTrue)