util/paging: choose min paging size default value as 128, and max value as 8192 (#36331)

close #36328

Author: tiancaiamao

util/paging/paging.go

@@ -17,16 +17,15 @@ package paging
 import "math"
 
 // A paging request may be separated into multi requests if there are more data than a page.
-// The paging size grows from min to max, it's not well tuned yet.
-// e.g. a paging request scans over range (r1, r200), it requires 64 rows in the first batch,
+// The paging size grows from min to max. See https://github.com/pingcap/tidb/issues/36328
+// e.g. a paging request scans over range (r1, r200), it requires 128 rows in the first batch,
 // if it's not drained, then the paging size grows, the new range is calculated like (r100, r200), then send a request again.
 // Compare with the common unary request, paging request allows early access of data, it offers a streaming-like way processing data.
-// TODO: may make the paging parameters configurable.
 const (
-	MinPagingSize      uint64 = 64
+	MinPagingSize      uint64 = 128
 	maxPagingSizeShift        = 7
 	pagingSizeGrow            = 2
-	MaxPagingSize             = MinPagingSize << maxPagingSizeShift
+	MaxPagingSize             = 8192
 	pagingGrowingSum          = ((2 << maxPagingSizeShift) - 1) * MinPagingSize
 	Threshold          uint64 = 960
 )

util/paging/paging_test.go

@@ -22,8 +22,8 @@ import (
 
 func TestGrowPagingSize(t *testing.T) {
 	require.Equal(t, GrowPagingSize(MinPagingSize), MinPagingSize*pagingSizeGrow)
-	require.Equal(t, GrowPagingSize(MaxPagingSize), MaxPagingSize)
-	require.Equal(t, GrowPagingSize(MaxPagingSize/pagingSizeGrow+1), MaxPagingSize)
+	require.Equal(t, GrowPagingSize(MaxPagingSize), uint64(MaxPagingSize))
+	require.Equal(t, GrowPagingSize(MaxPagingSize/pagingSizeGrow+1), uint64(MaxPagingSize))
 }
 
 func TestCalculateSeekCnt(t *testing.T) {