Fix small segment compaction (#21327)

Signed-off-by: xige-16 <xi.ge@zilliz.com>

configs/milvus.yaml

@@ -338,7 +338,7 @@ dataCoord:
     smallProportion: 0.5 # The segment is considered as "small segment" when its # of rows is smaller than
     # (smallProportion * segment max # of rows).
     # A compaction will happen on small segments if the segment after compaction will have
-    compactableProportion: 0.5
+    compactableProportion: 0.85
     # over (compactableProportion * segment max # of rows) rows.
     # MUST BE GREATER THAN OR EQUAL TO <smallProportion>!!!
     # During compaction, the size of segment # of rows is able to exceed segment max # of rows by (expansionRate-1) * 100%.

internal/datacoord/compaction_trigger.go

@@ -654,8 +654,7 @@ func (t *compactionTrigger) generatePlans(segments []*SegmentInfo, force bool, i
 		}
 		// only merge if candidate number is large than MinSegmentToMerge or if target row is large enough
 		if len(bucket) >= Params.DataCoordCfg.MinSegmentToMerge.GetAsInt() ||
-			len(bucket) > 1 &&
+			len(bucket) > 1 && t.isCompactableSegment(targetRow, segment) {
-				targetRow > int64(float64(segment.GetMaxRowNum())*Params.DataCoordCfg.SegmentCompactableProportion.GetAsFloat()) {
 			plan := segmentsToPlan(bucket, compactTime)
 			log.Info("generate a plan for small candidates",
 				zap.Int64s("plan segmentIDs", lo.Map(bucket, getSegmentIDs)),
@@ -798,6 +797,18 @@ func (t *compactionTrigger) isSmallSegment(segment *SegmentInfo) bool {
 	return segment.GetNumOfRows() < int64(float64(segment.GetMaxRowNum())*Params.DataCoordCfg.SegmentSmallProportion.GetAsFloat())
 }
 
+func (t *compactionTrigger) isCompactableSegment(targetRow int64, segment *SegmentInfo) bool {
+	smallProportion := Params.DataCoordCfg.SegmentSmallProportion.GetAsFloat()
+	compactableProportion := Params.DataCoordCfg.SegmentCompactableProportion.GetAsFloat()
+
+	// avoid invalid single segment compaction
+	if compactableProportion < smallProportion {
+		compactableProportion = smallProportion
+	}
+
+	return targetRow > int64(float64(segment.GetMaxRowNum())*compactableProportion)
+}
+
 func isExpandableSmallSegment(segment *SegmentInfo) bool {
 	return segment.GetNumOfRows() < int64(float64(segment.GetMaxRowNum())*(Params.DataCoordCfg.SegmentExpansionRate.GetAsFloat()-1))
 }

internal/datacoord/compaction_trigger_test.go

@@ -1156,8 +1156,8 @@ func Test_compactionTrigger_PrioritizedCandi(t *testing.T) {
 			spy := (tt.fields.compactionHandler).(*spyCompactionHandler)
 			select {
 			case val := <-spy.spyChan:
-				// 5 segments in the final pick list
+				// 6 segments in the final pick list
-				assert.Equal(t, len(val.SegmentBinlogs), 5)
+				assert.Equal(t, len(val.SegmentBinlogs), 6)
 				return
 			case <-time.After(3 * time.Second):
 				assert.Fail(t, "failed to get plan")

pkg/util/paramtable/component_param.go

@@ -2177,7 +2177,7 @@ the number of binlog file reaches to max value.`,
 	p.SegmentCompactableProportion = ParamItem{
 		Key:          "dataCoord.segment.compactableProportion",
 		Version:      "2.2.1",
-		DefaultValue: "0.5",
+		DefaultValue: "0.85",
 		Doc: `(smallProportion * segment max # of rows).
 A compaction will happen on small segments if the segment after compaction will have`,
 		Export: true,