*: use generics to improve Clamp (#34586)

close #34588

br/pkg/task/restore.go

@@ -23,6 +23,7 @@ import (
 	"github.com/pingcap/tidb/br/pkg/version"
 	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/kv"
+	"github.com/pingcap/tidb/util/mathutil"
 	"github.com/spf13/cobra"
 	"github.com/spf13/pflag"
 	"go.uber.org/multierr"
@@ -561,7 +562,7 @@ func RunRestore(c context.Context, g glue.Glue, cmdName string, cfg *RestoreConf
 	}
 
 	// Restore sst files in batch.
-	batchSize := utils.ClampInt(int(cfg.Concurrency), defaultRestoreConcurrency, maxRestoreBatchSizeLimit)
+	batchSize := mathutil.Clamp(int(cfg.Concurrency), defaultRestoreConcurrency, maxRestoreBatchSizeLimit)
 	failpoint.Inject("small-batch-size", func(v failpoint.Value) {
 		log.Info("failpoint small batch size is on", zap.Int("size", v.(int)))
 		batchSize = v.(int)

br/pkg/utils/math.go

@@ -2,21 +2,6 @@
 
 package utils
 
-import (
-	"github.com/pingcap/log"
-	"github.com/pingcap/tidb/util/mathutil"
-	"go.uber.org/zap"
-)
-
-// ClampInt restrict a value to a certain interval.
-func ClampInt(n, min, max int) int {
-	if min > max {
-		log.Error("clamping integer with min > max", zap.Int("min", min), zap.Int("max", max))
-	}
-
-	return mathutil.Min(max, mathutil.Max(min, n))
-}
-
 // NextPowerOfTwo returns the smallest power of two greater than or equal to `i`
 // Caller should guarantee that i > 0 and the return value is not overflow.
 func NextPowerOfTwo(i int64) int64 {

br/pkg/utils/math_test.go

@@ -8,14 +8,6 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestClampInt(t *testing.T) {
-	require.Equal(t, 3, ClampInt(100, 1, 3))
-	require.Equal(t, 2, ClampInt(2, 1, 3))
-	require.Equal(t, 1, ClampInt(0, 1, 3))
-	require.Equal(t, 1, ClampInt(0, 1, 1))
-	require.Equal(t, 1, ClampInt(100, 1, 1))
-}
-
 func TestNextPowerOfTwo(t *testing.T) {
 	require.Equal(t, int64(1), NextPowerOfTwo(1))
 	require.Equal(t, int64(4), NextPowerOfTwo(3))

statistics/histogram.go

@@ -40,6 +40,7 @@ import (
 	"github.com/pingcap/tidb/util/codec"
 	"github.com/pingcap/tidb/util/collate"
 	"github.com/pingcap/tidb/util/logutil"
+	"github.com/pingcap/tidb/util/mathutil"
 	"github.com/pingcap/tidb/util/ranger"
 	"github.com/pingcap/tipb/go-tipb"
 	"github.com/twmb/murmur3"
@@ -1278,7 +1279,7 @@ func (c *Column) GetColumnRowCount(sctx sessionctx.Context, ranges []*ranger.Ran
 				return 0, errors.Trace(err)
 			}
 			cnt -= lowCnt
-			cnt = clampRowCount(cnt, c.notNullCount())
+			cnt = mathutil.Clamp(cnt, 0, c.notNullCount())
 		}
 		if !rg.LowExclude && lowVal.IsNull() {
 			cnt += float64(c.NullCount)
@@ -1291,7 +1292,7 @@ func (c *Column) GetColumnRowCount(sctx sessionctx.Context, ranges []*ranger.Ran
 			cnt += highCnt
 		}
 
-		cnt = clampRowCount(cnt, c.TotalRowCount())
+		cnt = mathutil.Clamp(cnt, 0, c.TotalRowCount())
 
 		// If the current table row count has changed, we should scale the row count accordingly.
 		cnt *= c.GetIncreaseFactor(realtimeRowCount)
@@ -1307,8 +1308,7 @@ func (c *Column) GetColumnRowCount(sctx sessionctx.Context, ranges []*ranger.Ran
 
 		rowCount += cnt
 	}
-
-	rowCount = clampRowCount(rowCount, float64(realtimeRowCount))
+	rowCount = mathutil.Clamp(rowCount, 0, float64(realtimeRowCount))
 	return rowCount, nil
 }
 
@@ -1525,8 +1525,7 @@ func (idx *Index) GetRowCount(sctx sessionctx.Context, coll *HistColl, indexRang
 			totalCount += idx.Histogram.outOfRangeRowCount(&l, &r, increaseCount)
 		}
 	}
-
-	totalCount = clampRowCount(totalCount, float64(realtimeRowCount))
+	totalCount = mathutil.Clamp(totalCount, 0, float64(realtimeRowCount))
 	return totalCount, nil
 }
 
@@ -1781,16 +1780,6 @@ func (idx *Index) outOfRange(val types.Datum) bool {
 	return true
 }
 
-func clampRowCount(rowCount, upperLimit float64) (clampedRowCount float64) {
-	if rowCount > upperLimit {
-		return upperLimit
-	}
-	if rowCount < 0 {
-		return 0
-	}
-	return rowCount
-}
-
 // matchPrefix checks whether ad is the prefix of value
 func matchPrefix(row chunk.Row, colIdx int, ad *types.Datum) bool {
 	switch ad.Kind() {

util/mathutil/math.go

@@ -88,3 +88,13 @@ func Min[v constraints.Ordered](x v, xs ...v) v {
 	}
 	return min
 }
+
+// Clamp restrict a value to a certain interval.
+func Clamp[v constraints.Integer | constraints.Float](n, min, max v) v {
+	if n >= max {
+		return max
+	} else if n <= min {
+		return min
+	}
+	return n
+}

util/mathutil/math_test.go

@@ -71,3 +71,11 @@ func TestMaxMin(t *testing.T) {
 	require.Equal(t, "xy", Max("ab", "xy"))
 	require.Equal(t, "ab", Max("ab", "ab"))
 }
+
+func TestClamp(t *testing.T) {
+	require.Equal(t, 3, Clamp(100, 1, 3))
+	require.Equal(t, 2.0, Clamp(float64(2), 1.0, 3.0))
+	require.Equal(t, float32(1.0), Clamp(float32(0), 1.0, 3.0))
+	require.Equal(t, 1, Clamp(0, 1, 1))
+	require.Equal(t, 1, Clamp(100, 1, 1))
+}