Adding upstream version 2.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

search/searcher/optimize_knn.go

@@ -0,0 +1,53 @@
+//  Copyright (c) 2023 Couchbase, Inc.
+//
+// Licensed 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.
+
+//go:build vectors
+// +build vectors
+
+package searcher
+
+import (
+	"context"
+
+	"github.com/blevesearch/bleve/v2/search"
+	index "github.com/blevesearch/bleve_index_api"
+)
+
+func optimizeKNN(ctx context.Context, indexReader index.IndexReader,
+	qsearchers []search.Searcher) error {
+	var octx index.VectorOptimizableContext
+	var err error
+
+	for _, searcher := range qsearchers {
+		// Only applicable to KNN Searchers.
+		o, ok := searcher.(index.VectorOptimizable)
+		if !ok {
+			continue
+		}
+
+		octx, err = o.VectorOptimize(ctx, octx)
+		if err != nil {
+			return err
+		}
+	}
+
+	// No KNN searchers.
+	if octx == nil {
+		return nil
+	}
+
+	// Postings lists and iterators replaced in the pointer to the
+	// vector reader
+	return octx.Finish()
+}