Adding upstream version 2.5.1.

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

search/searcher/search_term_prefix.go

@@ -0,0 +1,86 @@
+//  Copyright (c) 2014 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.
+
+package searcher
+
+import (
+	"context"
+	"strings"
+
+	"github.com/blevesearch/bleve/v2/search"
+	index "github.com/blevesearch/bleve_index_api"
+)
+
+func NewTermPrefixSearcher(ctx context.Context, indexReader index.IndexReader, prefix string,
+	field string, boost float64, options search.SearcherOptions) (
+	search.Searcher, error) {
+	// find the terms with this prefix
+	fieldDict, err := indexReader.FieldDictPrefix(field, []byte(prefix))
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		if cerr := fieldDict.Close(); cerr != nil && err == nil {
+			err = cerr
+		}
+	}()
+
+	var terms []string
+	var termSet = make(map[string]struct{})
+	tfd, err := fieldDict.Next()
+	for err == nil && tfd != nil {
+		if _, exists := termSet[tfd.Term]; !exists {
+			termSet[tfd.Term] = struct{}{}
+			terms = append(terms, tfd.Term)
+			if tooManyClauses(len(terms)) {
+				return nil, tooManyClausesErr(field, len(terms))
+			}
+			tfd, err = fieldDict.Next()
+		}
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	if ctx != nil {
+		reportIOStats(ctx, fieldDict.BytesRead())
+		search.RecordSearchCost(ctx, search.AddM, fieldDict.BytesRead())
+	}
+
+	if ctx != nil {
+		if fts, ok := ctx.Value(search.FieldTermSynonymMapKey).(search.FieldTermSynonymMap); ok {
+			if ts, exists := fts[field]; exists {
+				for term := range ts {
+					if _, exists := termSet[term]; exists {
+						continue
+					}
+					if strings.HasPrefix(term, prefix) {
+						termSet[term] = struct{}{}
+						terms = append(terms, term)
+						if tooManyClauses(len(terms)) {
+							return nil, tooManyClausesErr(field, len(terms))
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// check if the terms are empty or have one term which is the prefix itself
+	if len(terms) == 0 || (len(terms) == 1 && terms[0] == prefix) {
+		return NewTermSearcher(ctx, indexReader, prefix, field, boost, options)
+	}
+
+	return NewMultiTermSearcher(ctx, indexReader, terms, field, boost, options, true)
+}