chore: import upstream snapshot with attribution

internal/flushcommon/writebuffer/stats_buffer.go

@@ -0,0 +1,48 @@
+// Licensed to the LF AI & Data foundation under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package writebuffer
+
+import (
+	"github.com/milvus-io/milvus/internal/storage"
+)
+
+// stats buffer used for bm25 stats
+type statsBuffer struct {
+	bm25Stats map[int64]*storage.BM25Stats
+}
+
+func (b *statsBuffer) Buffer(stats map[int64]*storage.BM25Stats) {
+	for fieldID, stat := range stats {
+		if fieldMeta, ok := b.bm25Stats[fieldID]; ok {
+			fieldMeta.Merge(stat)
+		} else {
+			b.bm25Stats[fieldID] = stat
+		}
+	}
+}
+
+func (b *statsBuffer) yieldBuffer() map[int64]*storage.BM25Stats {
+	result := b.bm25Stats
+	b.bm25Stats = make(map[int64]*storage.BM25Stats)
+	return result
+}
+
+func newStatsBuffer() *statsBuffer {
+	return &statsBuffer{
+		bm25Stats: make(map[int64]*storage.BM25Stats),
+	}
+}