Adding upstream version 2.5.1.

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

search/searcher/search_disjunction.go

@@ -0,0 +1,131 @@
+//  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 searcher
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/blevesearch/bleve/v2/search"
+	index "github.com/blevesearch/bleve_index_api"
+)
+
+// DisjunctionMaxClauseCount is a compile time setting that applications can
+// adjust to non-zero value to cause the DisjunctionSearcher to return an
+// error instead of exeucting searches when the size exceeds this value.
+var DisjunctionMaxClauseCount = 0
+
+// DisjunctionHeapTakeover is a compile time setting that applications can
+// adjust to control when the DisjunctionSearcher will switch from a simple
+// slice implementation to a heap implementation.
+var DisjunctionHeapTakeover = 10
+
+func NewDisjunctionSearcher(ctx context.Context, indexReader index.IndexReader,
+	qsearchers []search.Searcher, min float64, options search.SearcherOptions) (
+	search.Searcher, error) {
+	return newDisjunctionSearcher(ctx, indexReader, qsearchers, min, options, true)
+}
+
+func optionsDisjunctionOptimizable(options search.SearcherOptions) bool {
+	rv := options.Score == "none" && !options.IncludeTermVectors
+	return rv
+}
+
+func newDisjunctionSearcher(ctx context.Context, indexReader index.IndexReader,
+	qsearchers []search.Searcher, min float64, options search.SearcherOptions,
+	limit bool) (search.Searcher, error) {
+
+	var disjOverKNN bool
+	if ctx != nil {
+		disjOverKNN, _ = ctx.Value(search.IncludeScoreBreakdownKey).(bool)
+	}
+	if disjOverKNN {
+		// The KNN Searcher optimization is a necessary pre-req for the KNN Searchers,
+		// not an optional optimization like for, say term searchers.
+		// It's an optimization to repeat search an open vector index when applicable,
+		// rather than individually opening and searching a vector index.
+		err := optimizeKNN(ctx, indexReader, qsearchers)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		// attempt the "unadorned" disjunction optimization only when we
+		// do not need extra information like freq-norm's or term vectors
+		// and the requested min is simple
+		if len(qsearchers) > 1 && min <= 1 &&
+			optionsDisjunctionOptimizable(options) {
+			rv, err := optimizeCompositeSearcher(ctx, "disjunction:unadorned",
+				indexReader, qsearchers, options)
+			if err != nil || rv != nil {
+				return rv, err
+			}
+		}
+	}
+
+	if len(qsearchers) > DisjunctionHeapTakeover {
+		return newDisjunctionHeapSearcher(ctx, indexReader, qsearchers, min, options,
+			limit)
+	}
+	return newDisjunctionSliceSearcher(ctx, indexReader, qsearchers, min, options,
+		limit)
+}
+
+func optimizeCompositeSearcher(ctx context.Context, optimizationKind string,
+	indexReader index.IndexReader, qsearchers []search.Searcher,
+	options search.SearcherOptions) (search.Searcher, error) {
+	var octx index.OptimizableContext
+
+	for _, searcher := range qsearchers {
+		o, ok := searcher.(index.Optimizable)
+		if !ok {
+			return nil, nil
+		}
+
+		var err error
+		octx, err = o.Optimize(optimizationKind, octx)
+		if err != nil {
+			return nil, err
+		}
+
+		if octx == nil {
+			return nil, nil
+		}
+	}
+
+	optimized, err := octx.Finish()
+	if err != nil || optimized == nil {
+		return nil, err
+	}
+
+	tfr, ok := optimized.(index.TermFieldReader)
+	if !ok {
+		return nil, nil
+	}
+
+	return newTermSearcherFromReader(ctx, indexReader, tfr,
+		[]byte(optimizationKind), "*", 1.0, options)
+}
+
+func tooManyClauses(count int) bool {
+	if DisjunctionMaxClauseCount != 0 && count > DisjunctionMaxClauseCount {
+		return true
+	}
+	return false
+}
+
+func tooManyClausesErr(field string, count int) error {
+	return fmt.Errorf("TooManyClauses over field: `%s` [%d > maxClauseCount,"+
+		" which is set to %d]", field, count, DisjunctionMaxClauseCount)
+}