diff --git a/docs/developer_guides/chap07_query_coordinator.md b/docs/developer_guides/chap07_query_coordinator.md
index 8891dab6d5..858f227074 100644
--- a/docs/developer_guides/chap07_query_coordinator.md
+++ b/docs/developer_guides/chap07_query_coordinator.md
@@ -253,6 +253,7 @@ type QueryNode interface {
 	ReleaseCollection(ctx context.Context, req *querypb.ReleaseCollectionRequest) (*commonpb.Status, error)
 	// ReleasePartitions notifies Proxy to release partitions' data
 	ReleasePartitions(ctx context.Context, req *querypb.ReleasePartitionsRequest) (*commonpb.Status, error)
+	// ReleaseSegments releases the data of the specified segments in QueryNode.
 	ReleaseSegments(ctx context.Context, req *querypb.ReleaseSegmentsRequest) (*commonpb.Status, error)
 	GetSegmentInfo(ctx context.Context, req *querypb.GetSegmentInfoRequest) (*querypb.GetSegmentInfoResponse, error)
 	GetMetrics(ctx context.Context, in *milvuspb.GetMetricsRequest, opts ...grpc.CallOption) (*milvuspb.GetMetricsResponse, error)