diff --git a/pkg/planner/core/collect_column_stats_usage.go b/pkg/planner/core/collect_column_stats_usage.go
index dde44d6ff5ff0..d3d5aa877721c 100644
--- a/pkg/planner/core/collect_column_stats_usage.go
+++ b/pkg/planner/core/collect_column_stats_usage.go
@@ -347,7 +347,7 @@ func (c *columnStatsUsageCollector) collectFromPlan(lp base.LogicalPlan) {
 
 // CollectColumnStatsUsage collects column stats usage from logical plan.
 // predicate indicates whether to collect predicate columns and histNeeded indicates whether to collect histogram-needed columns.
-// First return value: predicate columns (nil if predicate is false)
+// First return value: predicate columns
 // Second return value: histogram-needed columns (nil if histNeeded is false)
 // Third return value: ds.PhysicalTableID from all DataSource (always collected)
 func CollectColumnStatsUsage(lp base.LogicalPlan, histNeeded bool) (
diff --git a/pkg/session/session.go b/pkg/session/session.go
index 066dbc818910a..8eeebd640392b 100644
--- a/pkg/session/session.go
+++ b/pkg/session/session.go
@@ -416,9 +416,8 @@ func (s *session) UpdateColStatsUsage(predicateColumns []model.TableItemID) {
 	t := time.Now()
 	colMap := make(map[model.TableItemID]time.Time, len(predicateColumns))
 	for _, col := range predicateColumns {
-		if col.IsIndex {
-			continue
-		}
+		// TODO: Remove this assertion once it has been confirmed to operate correctly over a period of time.
+		intest.Assert(!col.IsIndex, "predicate column should only be table column")
 		colMap[col] = t
 	}
 	s.statsCollector.UpdateColStatsUsage(colMap)
diff --git a/pkg/statistics/histogram.go b/pkg/statistics/histogram.go
index 0db2e88a7ed5b..2b3f3225af8d1 100644
--- a/pkg/statistics/histogram.go
+++ b/pkg/statistics/histogram.go
@@ -422,37 +422,6 @@ func (hg *Histogram) StandardizeForV2AnalyzeIndex() {
 	hg.Bounds = c
 }
 
-// AddIdxVals adds the given values to the histogram.
-func (hg *Histogram) AddIdxVals(idxValCntPairs []TopNMeta) {
-	totalAddCnt := int64(0)
-	slices.SortFunc(idxValCntPairs, func(i, j TopNMeta) int {
-		return bytes.Compare(i.Encoded, j.Encoded)
-	})
-	for bktIdx, pairIdx := 0, 0; bktIdx < hg.Len(); bktIdx++ {
-		for pairIdx < len(idxValCntPairs) {
-			// If the current val smaller than current bucket's lower bound, skip it.
-			cmpResult := bytes.Compare(hg.Bounds.Column(0).GetBytes(bktIdx*2), idxValCntPairs[pairIdx].Encoded)
-			if cmpResult > 0 {
-				continue
-			}
-			// If the current val bigger than current bucket's upper bound, break.
-			cmpResult = bytes.Compare(hg.Bounds.Column(0).GetBytes(bktIdx*2+1), idxValCntPairs[pairIdx].Encoded)
-			if cmpResult < 0 {
-				break
-			}
-			totalAddCnt += int64(idxValCntPairs[pairIdx].Count)
-			hg.Buckets[bktIdx].NDV++
-			if cmpResult == 0 {
-				hg.Buckets[bktIdx].Repeat = int64(idxValCntPairs[pairIdx].Count)
-				pairIdx++
-				break
-			}
-			pairIdx++
-		}
-		hg.Buckets[bktIdx].Count += totalAddCnt
-	}
-}
-
 // ToString gets the string representation for the histogram.
 func (hg *Histogram) ToString(idxCols int) string {
 	strs := make([]string, 0, hg.Len()+1)