Upgrade blevesearch to v0.8.1 (#9177)

For #1441

a91b427b59

vendor/github.com/couchbase/vellum/levenshtein/levenshtein.go

@@ -0,0 +1,64 @@
+//  Copyright (c) 2018 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 levenshtein
+
+import "fmt"
+
+// StateLimit is the maximum number of states allowed
+const StateLimit = 10000
+
+// ErrTooManyStates is returned if you attempt to build a Levenshtein
+// automaton which requires too many states.
+var ErrTooManyStates = fmt.Errorf("dfa contains more than %d states",
+	StateLimit)
+
+// LevenshteinAutomatonBuilder wraps a precomputed
+// datastructure that allows to produce small (but not minimal) DFA.
+type LevenshteinAutomatonBuilder struct {
+	pDfa *ParametricDFA
+}
+
+// NewLevenshteinAutomatonBuilder creates a
+// reusable, threadsafe Levenshtein automaton builder.
+// `maxDistance` - maximum distance considered by the automaton.
+// `transposition` - assign a distance of 1 for transposition
+//
+// Building this automaton builder is computationally intensive.
+// While it takes only a few milliseconds for `d=2`, it grows
+// exponentially with `d`. It is only reasonable to `d <= 5`.
+func NewLevenshteinAutomatonBuilder(maxDistance uint8,
+	transposition bool) (*LevenshteinAutomatonBuilder, error) {
+	lnfa := newLevenshtein(maxDistance, transposition)
+
+	pdfa, err := fromNfa(lnfa)
+	if err != nil {
+		return nil, err
+	}
+
+	return &LevenshteinAutomatonBuilder{pDfa: pdfa}, nil
+}
+
+// BuildDfa builds the levenshtein automaton for serving
+// queries with a given edit distance.
+func (lab *LevenshteinAutomatonBuilder) BuildDfa(query string,
+	fuzziness uint8) (*DFA, error) {
+	return lab.pDfa.buildDfa(query, fuzziness, false)
+}
+
+// MaxDistance returns the MaxEdit distance supported by the
+// LevenshteinAutomatonBuilder builder.
+func (lab *LevenshteinAutomatonBuilder) MaxDistance() uint8 {
+	return lab.pDfa.maxDistance
+}