zpopmin

datastruct/sortedset/skiplist.go

@@ -281,7 +281,7 @@ func (skiplist *skiplist) getLastInScoreRange(min *ScoreBorder, max *ScoreBorder
 /*
  * return removed elements
  */
-func (skiplist *skiplist) RemoveRangeByScore(min *ScoreBorder, max *ScoreBorder) (removed []*Element) {
+func (skiplist *skiplist) RemoveRangeByScore(min *ScoreBorder, max *ScoreBorder, limit int) (removed []*Element) {
 	update := make([]*node, maxLevel)
 	removed = make([]*Element, 0)
 	// find backward nodes (of target range) or last node of each level
@@ -308,6 +308,9 @@ func (skiplist *skiplist) RemoveRangeByScore(min *ScoreBorder, max *ScoreBorder)
 		removedElement := node.Element
 		removed = append(removed, &removedElement)
 		skiplist.removeNode(node, update)
+		if limit > 0 && len(removed) == limit {
+			break
+		}
 		node = next
 	}
 	return removed

datastruct/sortedset/sortedset.go

@@ -204,13 +204,29 @@ func (sortedSet *SortedSet) RangeByScore(min *ScoreBorder, max *ScoreBorder, off
 
 // RemoveByScore removes members which score within the given border
 func (sortedSet *SortedSet) RemoveByScore(min *ScoreBorder, max *ScoreBorder) int64 {
-	removed := sortedSet.skiplist.RemoveRangeByScore(min, max)
+	removed := sortedSet.skiplist.RemoveRangeByScore(min, max, 0)
 	for _, element := range removed {
 		delete(sortedSet.dict, element.Member)
 	}
 	return int64(len(removed))
 }
 
+func (sortedSet *SortedSet) PopMin(count int) []*Element {
+	first := sortedSet.skiplist.getFirstInScoreRange(negativeInfBorder, positiveInfBorder)
+	if first == nil {
+		return nil
+	}
+	border := &ScoreBorder{
+		Value:   first.Score,
+		Exclude: false,
+	}
+	removed := sortedSet.skiplist.RemoveRangeByScore(border, border, count)
+	for _, element := range removed {
+		delete(sortedSet.dict, element.Member)
+	}
+	return removed
+}
+
 // RemoveByRank removes member ranking within [start, stop)
 // sort by ascending order and rank starts from 0
 func (sortedSet *SortedSet) RemoveByRank(start int64, stop int64) int64 {