Remove x/net/context vendor by using std package (#5202)

* Update dep github.com/markbates/goth

* Update dep github.com/blevesearch/bleve

* Update dep golang.org/x/oauth2

* Fix github.com/blevesearch/bleve to c74e08f039

* Update dep golang.org/x/oauth2

Gopkg.lock

   revision = "3a771d992973f24aa725d07868b467d1ddfceafb"
 
 [[projects]]
-  digest = "1:67351095005f164e748a5a21899d1403b03878cb2d40a7b0f742376e6eeda974"
+  digest = "1:c10f35be6200b09e26da267ca80f837315093ecaba27e7a223071380efb9dd32"
   name = "github.com/blevesearch/bleve"
   packages = [
     ".",
     "search/searcher",
   ]
   pruneopts = "NUT"
-  revision = "ff210fbc6d348ad67aa5754eaea11a463fcddafd"
+  revision = "c74e08f039e56cef576e4336382b2a2d12d9e026"
 
 [[projects]]
   branch = "master"
   revision = "e3534c89ef969912856dfa39e56b09e58c5f5daf"
 
 [[projects]]
-  digest = "1:23f75ae90fcc38dac6fad6881006ea7d0f2c78db5f9f81f3df558dc91460e61f"
+  digest = "1:4b992ec853d0ea9bac3dcf09a64af61de1a392e6cb0eef2204c0c92f4ae6b911"
   name = "github.com/markbates/goth"
   packages = [
     ".",
     "providers/twitter",
   ]
   pruneopts = "NUT"
-  revision = "f9c6649ab984d6ea71ef1e13b7b1cdffcf4592d3"
-  version = "v1.46.1"
+  revision = "bc6d8ddf751a745f37ca5567dbbfc4157bbf5da9"
+  version = "v1.47.2"
 
 [[projects]]
   digest = "1:c9724c929d27a14475a45b17a267dbc60671c0bc2c5c05ed21f011f7b5bc9fb5"
 
 [[projects]]
   branch = "master"
-  digest = "1:6d5ed712653ea5321fe3e3475ab2188cf362a4e0d31e9fd3acbd4dfbbca0d680"
+  digest = "1:d0a0bdd2b64d981aa4e6a1ade90431d042cd7fa31b584e33d45e62cbfec43380"
   name = "golang.org/x/net"
   packages = [
     "context",
+    "context/ctxhttp",
     "html",
     "html/atom",
     "html/charset",
   revision = "9b4f9f5ad5197c79fd623a3638e70d8b26cef344"
 
 [[projects]]
-  digest = "1:8159a9cda4b8810aaaeb0d60e2fa68e2fd86d8af4ec8f5059830839e3c8d93d5"
+  branch = "master"
+  digest = "1:274a6321a5a9f185eeb3fab5d7d8397e0e9f57737490d749f562c7e205ffbc2e"
   name = "golang.org/x/oauth2"
   packages = [
     ".",
     "internal",
   ]
   pruneopts = "NUT"
-  revision = "c10ba270aa0bf8b8c1c986e103859c67a9103061"
+  revision = "c453e0c757598fd055e170a3a359263c91e13153"
 
 [[projects]]
   digest = "1:9f303486d623f840492bfeb48eb906a94e9d3fe638a761639b72ce64bf7bfcc3"

Gopkg.toml

   branch = "master"
   name = "code.gitea.io/sdk"
 
+[[constraint]]
+#  branch = "master"
+  revision = "c74e08f039e56cef576e4336382b2a2d12d9e026"
+  name = "github.com/blevesearch/bleve"
+#Not targetting v0.7.0 since standard where use only just after this tag
+
 [[constraint]]
   revision = "12dd70caea0268ac0d6c2707d0611ef601e7c64e"
   name = "golang.org/x/crypto"
 
 [[constraint]]
   name = "github.com/markbates/goth"
-  version = "1.46.1"
+  version = "1.47.2"
 
 [[constraint]]
   branch = "master"
   source = "github.com/go-gitea/bolt"
 
 [[override]]
-  revision = "c10ba270aa0bf8b8c1c986e103859c67a9103061"
+  branch = "master"
   name = "golang.org/x/oauth2"
 
 [[constraint]]

vendor/github.com/blevesearch/bleve/index.go

 package bleve
 
 import (
+	"context"
+
 	"github.com/blevesearch/bleve/document"
 	"github.com/blevesearch/bleve/index"
 	"github.com/blevesearch/bleve/index/store"
 	"github.com/blevesearch/bleve/mapping"
-	"golang.org/x/net/context"
 )
 
 // A Batch groups together multiple Index and Delete

vendor/github.com/blevesearch/bleve/index/scorch/introducer.go

 	// prepare new index snapshot
 	newSnapshot := &IndexSnapshot{
 		parent:   s,
-		segment:  make([]*SegmentSnapshot, nsegs, nsegs+1),
-		offsets:  make([]uint64, nsegs, nsegs+1),
+		segment:  make([]*SegmentSnapshot, 0, nsegs+1),
+		offsets:  make([]uint64, 0, nsegs+1),
 		internal: make(map[string][]byte, len(s.root.internal)),
 		epoch:    s.nextSnapshotEpoch,
 		refs:     1,
 				return err
 			}
 		}
-		newSnapshot.segment[i] = &SegmentSnapshot{
+
+		newss := &SegmentSnapshot{
 			id:         s.root.segment[i].id,
 			segment:    s.root.segment[i].segment,
 			cachedDocs: s.root.segment[i].cachedDocs,
 		}
-		s.root.segment[i].segment.AddRef()
 
 		// apply new obsoletions
 		if s.root.segment[i].deleted == nil {
-			newSnapshot.segment[i].deleted = delta
+			newss.deleted = delta
 		} else {
-			newSnapshot.segment[i].deleted = roaring.Or(s.root.segment[i].deleted, delta)
+			newss.deleted = roaring.Or(s.root.segment[i].deleted, delta)
 		}
 
-		newSnapshot.offsets[i] = running
-		running += s.root.segment[i].Count()
-
+		// check for live size before copying
+		if newss.LiveSize() > 0 {
+			newSnapshot.segment = append(newSnapshot.segment, newss)
+			s.root.segment[i].segment.AddRef()
+			newSnapshot.offsets = append(newSnapshot.offsets, running)
+			running += s.root.segment[i].Count()
+		}
 	}
+
 	// append new segment, if any, to end of the new index snapshot
 	if next.data != nil {
 		newSegmentSnapshot := &SegmentSnapshot{
 	// prepare new index snapshot
 	currSize := len(s.root.segment)
 	newSize := currSize + 1 - len(nextMerge.old)
+
+	// empty segments deletion
+	if nextMerge.new == nil {
+		newSize--
+	}
+
 	newSnapshot := &IndexSnapshot{
 		parent:   s,
 		segment:  make([]*SegmentSnapshot, 0, newSize),
 		segmentID := s.root.segment[i].id
 		if segSnapAtMerge, ok := nextMerge.old[segmentID]; ok {
 			// this segment is going away, see if anything else was deleted since we started the merge
-			if s.root.segment[i].deleted != nil {
+			if segSnapAtMerge != nil && s.root.segment[i].deleted != nil {
 				// assume all these deletes are new
 				deletedSince := s.root.segment[i].deleted
 				// if we already knew about some of them, remove
 					newSegmentDeleted.Add(uint32(newDocNum))
 				}
 			}
-		} else {
+			// clean up the old segment map to figure out the
+			// obsolete segments wrt root in meantime, whatever
+			// segments left behind in old map after processing
+			// the root segments would be the obsolete segment set
+			delete(nextMerge.old, segmentID)
+
+		} else if s.root.segment[i].LiveSize() > 0 {
 			// this segment is staying
 			newSnapshot.segment = append(newSnapshot.segment, &SegmentSnapshot{
 				id:         s.root.segment[i].id,
 		}
 	}
 
-	// put new segment at end
-	newSnapshot.segment = append(newSnapshot.segment, &SegmentSnapshot{
-		id:         nextMerge.id,
-		segment:    nextMerge.new, // take ownership for nextMerge.new's ref-count
-		deleted:    newSegmentDeleted,
-		cachedDocs: &cachedDocs{cache: nil},
-	})
-	newSnapshot.offsets = append(newSnapshot.offsets, running)
+	// before the newMerge introduction, need to clean the newly
+	// merged segment wrt the current root segments, hence
+	// applying the obsolete segment contents to newly merged segment
+	for segID, ss := range nextMerge.old {
+		obsoleted := ss.DocNumbersLive()
+		if obsoleted != nil {
+			obsoletedIter := obsoleted.Iterator()
+			for obsoletedIter.HasNext() {
+				oldDocNum := obsoletedIter.Next()
+				newDocNum := nextMerge.oldNewDocNums[segID][oldDocNum]
+				newSegmentDeleted.Add(uint32(newDocNum))
+			}
+		}
+	}
+	// In case where all the docs in the newly merged segment getting
+	// deleted by the time we reach here, can skip the introduction.
+	if nextMerge.new != nil &&
+		nextMerge.new.Count() > newSegmentDeleted.GetCardinality() {
+		// put new segment at end
+		newSnapshot.segment = append(newSnapshot.segment, &SegmentSnapshot{
+			id:         nextMerge.id,
+			segment:    nextMerge.new, // take ownership for nextMerge.new's ref-count
+			deleted:    newSegmentDeleted,
+			cachedDocs: &cachedDocs{cache: nil},
+		})
+		newSnapshot.offsets = append(newSnapshot.offsets, running)
+	}
+
+	newSnapshot.AddRef() // 1 ref for the nextMerge.notify response
 
 	// swap in new segment
 	rootPrev := s.root
 		_ = rootPrev.DecRef()
 	}
 
-	// notify merger we incorporated this
+	// notify requester that we incorporated this
+	nextMerge.notify <- newSnapshot
 	close(nextMerge.notify)
 }
 

vendor/github.com/blevesearch/bleve/index/scorch/merge.go

 package scorch
 
 import (
+	"bytes"
+	"encoding/json"
+
 	"fmt"
 	"os"
 	"sync/atomic"
 
 func (s *Scorch) mergerLoop() {
 	var lastEpochMergePlanned uint64
+	mergePlannerOptions, err := s.parseMergePlannerOptions()
+	if err != nil {
+		s.fireAsyncError(fmt.Errorf("mergePlannerOption json parsing err: %v", err))
+		s.asyncTasks.Done()
+		return
+	}
+
 OUTER:
 	for {
 		select {
 				startTime := time.Now()
 
 				// lets get started
-				err := s.planMergeAtSnapshot(ourSnapshot)
+				err := s.planMergeAtSnapshot(ourSnapshot, mergePlannerOptions)
 				if err != nil {
 					s.fireAsyncError(fmt.Errorf("merging err: %v", err))
 					_ = ourSnapshot.DecRef()
 			_ = ourSnapshot.DecRef()
 
 			// tell the persister we're waiting for changes
-			// first make a notification chan
-			notifyUs := make(notificationChan)
+			// first make a epochWatcher chan
+			ew := &epochWatcher{
+				epoch:    lastEpochMergePlanned,
+				notifyCh: make(notificationChan, 1),
+			}
 
 			// give it to the persister
 			select {
 			case <-s.closeCh:
 				break OUTER
-			case s.persisterNotifier <- notifyUs:
-			}
-
-			// check again
-			s.rootLock.RLock()
-			ourSnapshot = s.root
-			ourSnapshot.AddRef()
-			s.rootLock.RUnlock()
-
-			if ourSnapshot.epoch != lastEpochMergePlanned {
-				startTime := time.Now()
-
-				// lets get started
-				err := s.planMergeAtSnapshot(ourSnapshot)
-				if err != nil {
-					s.fireAsyncError(fmt.Errorf("merging err: %v", err))
-					_ = ourSnapshot.DecRef()
-					continue OUTER
-				}
-				lastEpochMergePlanned = ourSnapshot.epoch
-
-				s.fireEvent(EventKindMergerProgress, time.Since(startTime))
+			case s.persisterNotifier <- ew:
 			}
-			_ = ourSnapshot.DecRef()
 
-			// now wait for it (but also detect close)
+			// now wait for persister (but also detect close)
 			select {
 			case <-s.closeCh:
 				break OUTER
-			case <-notifyUs:
-				// woken up, next loop should pick up work
+			case <-ew.notifyCh:
 			}
 		}
 	}
 	s.asyncTasks.Done()
 }
 
-func (s *Scorch) planMergeAtSnapshot(ourSnapshot *IndexSnapshot) error {
+func (s *Scorch) parseMergePlannerOptions() (*mergeplan.MergePlanOptions,
+	error) {
+	mergePlannerOptions := mergeplan.DefaultMergePlanOptions
+	if v, ok := s.config["scorchMergePlanOptions"]; ok {
+		b, err := json.Marshal(v)
+		if err != nil {
+			return &mergePlannerOptions, err
+		}
+
+		err = json.Unmarshal(b, &mergePlannerOptions)
+		if err != nil {
+			return &mergePlannerOptions, err
+		}
+	}
+	return &mergePlannerOptions, nil
+}
+
+func (s *Scorch) planMergeAtSnapshot(ourSnapshot *IndexSnapshot,
+	options *mergeplan.MergePlanOptions) error {
 	// build list of zap segments in this snapshot
 	var onlyZapSnapshots []mergeplan.Segment
 	for _, segmentSnapshot := range ourSnapshot.segment {
 	}
 
 	// give this list to the planner
-	resultMergePlan, err := mergeplan.Plan(onlyZapSnapshots, nil)
+	resultMergePlan, err := mergeplan.Plan(onlyZapSnapshots, options)
 	if err != nil {
 		return fmt.Errorf("merge planning err: %v", err)
 	}
 	}
 
 	// process tasks in serial for now
-	var notifications []notificationChan
+	var notifications []chan *IndexSnapshot
 	for _, task := range resultMergePlan.Tasks {
+		if len(task.Segments) == 0 {
+			continue
+		}
+
 		oldMap := make(map[uint64]*SegmentSnapshot)
 		newSegmentID := atomic.AddUint64(&s.nextSegmentID, 1)
 		segmentsToMerge := make([]*zap.Segment, 0, len(task.Segments))
 			if segSnapshot, ok := planSegment.(*SegmentSnapshot); ok {
 				oldMap[segSnapshot.id] = segSnapshot
 				if zapSeg, ok := segSnapshot.segment.(*zap.Segment); ok {
-					segmentsToMerge = append(segmentsToMerge, zapSeg)
-					docsToDrop = append(docsToDrop, segSnapshot.deleted)
+					if segSnapshot.LiveSize() == 0 {
+						oldMap[segSnapshot.id] = nil
+					} else {
+						segmentsToMerge = append(segmentsToMerge, zapSeg)
+						docsToDrop = append(docsToDrop, segSnapshot.deleted)
+					}
 				}
 			}
 		}
 
-		filename := zapFileName(newSegmentID)
-		s.markIneligibleForRemoval(filename)
-		path := s.path + string(os.PathSeparator) + filename
-		newDocNums, err := zap.Merge(segmentsToMerge, docsToDrop, path, DefaultChunkFactor)
-		if err != nil {
-			s.unmarkIneligibleForRemoval(filename)
-			return fmt.Errorf("merging failed: %v", err)
-		}
-		segment, err := zap.Open(path)
-		if err != nil {
-			s.unmarkIneligibleForRemoval(filename)
-			return err
+		var oldNewDocNums map[uint64][]uint64
+		var segment segment.Segment
+		if len(segmentsToMerge) > 0 {
+			filename := zapFileName(newSegmentID)
+			s.markIneligibleForRemoval(filename)
+			path := s.path + string(os.PathSeparator) + filename
+			newDocNums, err := zap.Merge(segmentsToMerge, docsToDrop, path, 1024)
+			if err != nil {
+				s.unmarkIneligibleForRemoval(filename)
+				return fmt.Errorf("merging failed: %v", err)
+			}
+			segment, err = zap.Open(path)
+			if err != nil {
+				s.unmarkIneligibleForRemoval(filename)
+				return err
+			}
+			oldNewDocNums = make(map[uint64][]uint64)
+			for i, segNewDocNums := range newDocNums {
+				oldNewDocNums[task.Segments[i].Id()] = segNewDocNums
+			}
 		}
+
 		sm := &segmentMerge{
 			id:            newSegmentID,
 			old:           oldMap,
-			oldNewDocNums: make(map[uint64][]uint64),
+			oldNewDocNums: oldNewDocNums,
 			new:           segment,
-			notify:        make(notificationChan),
+			notify:        make(chan *IndexSnapshot, 1),
 		}
 		notifications = append(notifications, sm.notify)
-		for i, segNewDocNums := range newDocNums {
-			sm.oldNewDocNums[task.Segments[i].Id()] = segNewDocNums
-		}
 
 		// give it to the introducer
 		select {
 		case <-s.closeCh:
+			_ = segment.Close()
 			return nil
 		case s.merges <- sm:
 		}
 		select {
 		case <-s.closeCh:
 			return nil
-		case <-notification:
+		case newSnapshot := <-notification:
+			if newSnapshot != nil {
+				_ = newSnapshot.DecRef()
+			}
 		}
 	}
 	return nil
 	old           map[uint64]*SegmentSnapshot
 	oldNewDocNums map[uint64][]uint64
 	new           segment.Segment
-	notify        notificationChan
+	notify        chan *IndexSnapshot
+}
+
+// perform a merging of the given SegmentBase instances into a new,
+// persisted segment, and synchronously introduce that new segment
+// into the root
+func (s *Scorch) mergeSegmentBases(snapshot *IndexSnapshot,
+	sbs []*zap.SegmentBase, sbsDrops []*roaring.Bitmap, sbsIndexes []int,
+	chunkFactor uint32) (uint64, *IndexSnapshot, uint64, error) {
+	var br bytes.Buffer
+
+	cr := zap.NewCountHashWriter(&br)
+
+	newDocNums, numDocs, storedIndexOffset, fieldsIndexOffset,
+		docValueOffset, dictLocs, fieldsInv, fieldsMap, err :=
+		zap.MergeToWriter(sbs, sbsDrops, chunkFactor, cr)
+	if err != nil {
+		return 0, nil, 0, err
+	}
+
+	sb, err := zap.InitSegmentBase(br.Bytes(), cr.Sum32(), chunkFactor,
+		fieldsMap, fieldsInv, numDocs, storedIndexOffset, fieldsIndexOffset,
+		docValueOffset, dictLocs)
+	if err != nil {
+		return 0, nil, 0, err
+	}
+
+	newSegmentID := atomic.AddUint64(&s.nextSegmentID, 1)
+
+	filename := zapFileName(newSegmentID)
+	path := s.path + string(os.PathSeparator) + filename
+	err = zap.PersistSegmentBase(sb, path)
+	if err != nil {
+		return 0, nil, 0, err
+	}
+
+	segment, err := zap.Open(path)
+	if err != nil {
+		return 0, nil, 0, err
+	}
+
+	sm := &segmentMerge{
+		id:            newSegmentID,
+		old:           make(map[uint64]*SegmentSnapshot),
+		oldNewDocNums: make(map[uint64][]uint64),
+		new:           segment,
+		notify:        make(chan *IndexSnapshot, 1),
+	}
+
+	for i, idx := range sbsIndexes {
+		ss := snapshot.segment[idx]
+		sm.old[ss.id] = ss
+		sm.oldNewDocNums[ss.id] = newDocNums[i]
+	}
+
+	select { // send to introducer
+	case <-s.closeCh:
+		_ = segment.DecRef()
+		return 0, nil, 0, nil // TODO: return ErrInterruptedClosed?
+	case s.merges <- sm:
+	}
+
+	select { // wait for introduction to complete
+	case <-s.closeCh:
+		return 0, nil, 0, nil // TODO: return ErrInterruptedClosed?
+	case newSnapshot := <-sm.notify:
+		return numDocs, newSnapshot, newSegmentID, nil
+	}
 }

vendor/github.com/blevesearch/bleve/index/scorch/mergeplan/merge_plan.go

 
 	// While we’re over budget, keep looping, which might produce
 	// another MergeTask.
-	for len(eligibles) > budgetNumSegments {
+	for len(eligibles) > 0 && (len(eligibles)+len(rv.Tasks)) > budgetNumSegments {
 		// Track a current best roster as we examine and score
 		// potential rosters of merges.
 		var bestRoster []Segment
 		var bestRosterScore float64 // Lower score is better.
 
-		for startIdx := 0; startIdx < len(eligibles)-o.SegmentsPerMergeTask; startIdx++ {
+		for startIdx := 0; startIdx < len(eligibles); startIdx++ {
 			var roster []Segment
 			var rosterLiveSize int64
 

vendor/github.com/blevesearch/bleve/index/scorch/persister.go

 
 var DefaultChunkFactor uint32 = 1024
 
+// Arbitrary number, need to make it configurable.
+// Lower values like 10/making persister really slow
+// doesn't work well as it is creating more files to
+// persist for in next persist iteration and spikes the # FDs.
+// Ideal value should let persister also proceed at
+// an optimum pace so that the merger can skip
+// many intermediate snapshots.
+// This needs to be based on empirical data.
+// TODO - may need to revisit this approach/value.
+var epochDistance = uint64(5)
+
 type notificationChan chan struct{}
 
 func (s *Scorch) persisterLoop() {
 	defer s.asyncTasks.Done()
 
-	var notifyChs []notificationChan
-	var lastPersistedEpoch uint64
+	var persistWatchers []*epochWatcher
+	var lastPersistedEpoch, lastMergedEpoch uint64
+	var ew *epochWatcher
 OUTER:
 	for {
 		select {
 		case <-s.closeCh:
 			break OUTER
-		case notifyCh := <-s.persisterNotifier:
-			notifyChs = append(notifyChs, notifyCh)
+		case ew = <-s.persisterNotifier:
+			persistWatchers = append(persistWatchers, ew)
 		default:
 		}
+		if ew != nil && ew.epoch > lastMergedEpoch {
+			lastMergedEpoch = ew.epoch
+		}
+		persistWatchers = s.pausePersisterForMergerCatchUp(lastPersistedEpoch,
+			&lastMergedEpoch, persistWatchers)
 
 		var ourSnapshot *IndexSnapshot
 		var ourPersisted []chan error
 			}
 
 			lastPersistedEpoch = ourSnapshot.epoch
-			for _, notifyCh := range notifyChs {
-				close(notifyCh)
+			for _, ew := range persistWatchers {
+				close(ew.notifyCh)
 			}
-			notifyChs = nil
+
+			persistWatchers = nil
 			_ = ourSnapshot.DecRef()
 
 			changed := false
 			break OUTER
 		case <-w.notifyCh:
 			// woken up, next loop should pick up work
+			continue OUTER
+		case ew = <-s.persisterNotifier:
+			// if the watchers are already caught up then let them wait,
+			// else let them continue to do the catch up
+			persistWatchers = append(persistWatchers, ew)
+		}
+	}
+}
+
+func notifyMergeWatchers(lastPersistedEpoch uint64,
+	persistWatchers []*epochWatcher) []*epochWatcher {
+	var watchersNext []*epochWatcher
+	for _, w := range persistWatchers {
+		if w.epoch < lastPersistedEpoch {
+			close(w.notifyCh)
+		} else {
+			watchersNext = append(watchersNext, w)
 		}
 	}
+	return watchersNext
+}
+
+func (s *Scorch) pausePersisterForMergerCatchUp(lastPersistedEpoch uint64, lastMergedEpoch *uint64,
+	persistWatchers []*epochWatcher) []*epochWatcher {
+
+	// first, let the watchers proceed if they lag behind
+	persistWatchers = notifyMergeWatchers(lastPersistedEpoch, persistWatchers)
+
+OUTER:
+	// check for slow merger and await until the merger catch up
+	for lastPersistedEpoch > *lastMergedEpoch+epochDistance {
+
+		select {
+		case <-s.closeCh:
+			break OUTER
+		case ew := <-s.persisterNotifier:
+			persistWatchers = append(persistWatchers, ew)
+			*lastMergedEpoch = ew.epoch
+		}
+
+		// let the watchers proceed if they lag behind
+		persistWatchers = notifyMergeWatchers(lastPersistedEpoch, persistWatchers)
+	}
+
+	return persistWatchers
 }
 
 func (s *Scorch) persistSnapshot(snapshot *IndexSnapshot) error {
-	// start a write transaction
-	tx, err := s.rootBolt.Begin(true)
+	persisted, err := s.persistSnapshotMaybeMerge(snapshot)
 	if err != nil {
 		return err
 	}
-	// defer fsync of the rootbolt
-	defer func() {
-		if err == nil {
-			err = s.rootBolt.Sync()
+	if persisted {
+		return nil
+	}
+
+	return s.persistSnapshotDirect(snapshot)
+}
+
+// DefaultMinSegmentsForInMemoryMerge represents the default number of
+// in-memory zap segments that persistSnapshotMaybeMerge() needs to
+// see in an IndexSnapshot before it decides to merge and persist
+// those segments
+var DefaultMinSegmentsForInMemoryMerge = 2
+
+// persistSnapshotMaybeMerge examines the snapshot and might merge and
+// persist the in-memory zap segments if there are enough of them
+func (s *Scorch) persistSnapshotMaybeMerge(snapshot *IndexSnapshot) (
+	bool, error) {
+	// collect the in-memory zap segments (SegmentBase instances)
+	var sbs []*zap.SegmentBase
+	var sbsDrops []*roaring.Bitmap
+	var sbsIndexes []int
+
+	for i, segmentSnapshot := range snapshot.segment {
+		if sb, ok := segmentSnapshot.segment.(*zap.SegmentBase); ok {
+			sbs = append(sbs, sb)
+			sbsDrops = append(sbsDrops, segmentSnapshot.deleted)
+			sbsIndexes = append(sbsIndexes, i)
 		}
+	}
+
+	if len(sbs) < DefaultMinSegmentsForInMemoryMerge {
+		return false, nil
+	}
+
+	_, newSnapshot, newSegmentID, err := s.mergeSegmentBases(
+		snapshot, sbs, sbsDrops, sbsIndexes, DefaultChunkFactor)
+	if err != nil {
+		return false, err
+	}
+	if newSnapshot == nil {
+		return false, nil
+	}
+
+	defer func() {
+		_ = newSnapshot.DecRef()
 	}()
-	// defer commit/rollback transaction
+
+	mergedSegmentIDs := map[uint64]struct{}{}
+	for _, idx := range sbsIndexes {
+		mergedSegmentIDs[snapshot.segment[idx].id] = struct{}{}
+	}
+
+	// construct a snapshot that's logically equivalent to the input
+	// snapshot, but with merged segments replaced by the new segment
+	equiv := &IndexSnapshot{
+		parent:   snapshot.parent,
+		segment:  make([]*SegmentSnapshot, 0, len(snapshot.segment)),
+		internal: snapshot.internal,
+		epoch:    snapshot.epoch,
+	}
+
+	// copy to the equiv the segments that weren't replaced
+	for _, segment := range snapshot.segment {
+		if _, wasMerged := mergedSegmentIDs[segment.id]; !wasMerged {
+			equiv.segment = append(equiv.segment, segment)
+		}
+	}
+
+	// append to the equiv the new segment
+	for _, segment := range newSnapshot.segment {
+		if segment.id == newSegmentID {
+			equiv.segment = append(equiv.segment, &SegmentSnapshot{
+				id:      newSegmentID,
+				segment: segment.segment,
+				deleted: nil, // nil since merging handled deletions
+			})
+			break
+		}
+	}
+
+	err = s.persistSnapshotDirect(equiv)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}
+
+func (s *Scorch) persistSnapshotDirect(snapshot *IndexSnapshot) (err error) {
+	// start a write transaction
+	tx, err := s.rootBolt.Begin(true)
+	if err != nil {
+		return err
+	}
+	// defer rollback on error
 	defer func() {
-		if err == nil {
-			err = tx.Commit()
-		} else {
+		if err != nil {
 			_ = tx.Rollback()
 		}
 	}()
 	newSegmentPaths := make(map[uint64]string)
 
 	// first ensure that each segment in this snapshot has been persisted
-	for i, segmentSnapshot := range snapshot.segment {
-		snapshotSegmentKey := segment.EncodeUvarintAscending(nil, uint64(i))
-		snapshotSegmentBucket, err2 := snapshotBucket.CreateBucketIfNotExists(snapshotSegmentKey)
-		if err2 != nil {
-			return err2
+	for _, segmentSnapshot := range snapshot.segment {
+		snapshotSegmentKey := segment.EncodeUvarintAscending(nil, segmentSnapshot.id)
+		snapshotSegmentBucket, err := snapshotBucket.CreateBucketIfNotExists(snapshotSegmentKey)
+		if err != nil {
+			return err
 		}
 		switch seg := segmentSnapshot.segment.(type) {
 		case *zap.SegmentBase:
 			// need to persist this to disk
 			filename := zapFileName(segmentSnapshot.id)
 			path := s.path + string(os.PathSeparator) + filename
-			err2 := zap.PersistSegmentBase(seg, path)
-			if err2 != nil {
-				return fmt.Errorf("error persisting segment: %v", err2)
+			err = zap.PersistSegmentBase(seg, path)
+			if err != nil {
+				return fmt.Errorf("error persisting segment: %v", err)
 			}
 			newSegmentPaths[segmentSnapshot.id] = path
 			err = snapshotSegmentBucket.Put(boltPathKey, []byte(filename))
 		}
 	}
 
-	// only alter the root if we actually persisted a segment
-	// (sometimes its just a new snapshot, possibly with new internal values)
+	// we need to swap in a new root only when we've persisted 1 or
+	// more segments -- whereby the new root would have 1-for-1
+	// replacements of in-memory segments with file-based segments
+	//
+	// other cases like updates to internal values only, and/or when
+	// there are only deletions, are already covered and persisted by
+	// the newly populated boltdb snapshotBucket above
 	if len(newSegmentPaths) > 0 {
 		// now try to open all the new snapshots
 		newSegments := make(map[uint64]segment.Segment)
+		defer func() {
+			for _, s := range newSegments {
+				if s != nil {
+					// cleanup segments that were opened but not
+					// swapped into the new root
+					_ = s.Close()
+				}
+			}
+		}()
 		for segmentID, path := range newSegmentPaths {
 			newSegments[segmentID], err = zap.Open(path)
 			if err != nil {
-				for _, s := range newSegments {
-					if s != nil {
-						_ = s.Close() // cleanup segments that were successfully opened
-					}
-				}
 				return fmt.Errorf("error opening new segment at %s, %v", path, err)
 			}
 		}
 					cachedDocs: segmentSnapshot.cachedDocs,
 				}
 				newIndexSnapshot.segment[i] = newSegmentSnapshot
+				delete(newSegments, segmentSnapshot.id)
 				// update items persisted incase of a new segment snapshot
 				atomic.AddUint64(&s.stats.numItemsPersisted, newSegmentSnapshot.Count())
 			} else {
 		for k, v := range s.root.internal {
 			newIndexSnapshot.internal[k] = v
 		}
-		for _, filename := range filenames {
-			delete(s.ineligibleForRemoval, filename)
-		}
+
 		rootPrev := s.root
 		s.root = newIndexSnapshot
 		s.rootLock.Unlock()
 		}
 	}
 
+	err = tx.Commit()
+	if err != nil {
+		return err
+	}
+
+	err = s.rootBolt.Sync()
+	if err != nil {
+		return err
+	}
+
+	// allow files to become eligible for removal after commit, such
+	// as file segments from snapshots that came from the merger
+	s.rootLock.Lock()
+	for _, filename := range filenames {
+		delete(s.ineligibleForRemoval, filename)
+	}
+	s.rootLock.Unlock()
+
 	return nil
 }
 

vendor/github.com/blevesearch/bleve/index/scorch/scorch.go

 	merges             chan *segmentMerge
 	introducerNotifier chan *epochWatcher
 	revertToSnapshots  chan *snapshotReversion
-	persisterNotifier  chan notificationChan
+	persisterNotifier  chan *epochWatcher
 	rootBolt           *bolt.DB
 	asyncTasks         sync.WaitGroup
 
 }
 
 func (s *Scorch) Open() error {
+	err := s.openBolt()
+	if err != nil {
+		return err
+	}
+
+	s.asyncTasks.Add(1)
+	go s.mainLoop()
+
+	if !s.readOnly && s.path != "" {
+		s.asyncTasks.Add(1)
+		go s.persisterLoop()
+		s.asyncTasks.Add(1)
+		go s.mergerLoop()
+	}
+
+	return nil
+}
+
+func (s *Scorch) openBolt() error {
 	var ok bool
 	s.path, ok = s.config["path"].(string)
 	if !ok {
 			}
 		}
 	}
+
 	rootBoltPath := s.path + string(os.PathSeparator) + "root.bolt"
 	var err error
 	if s.path != "" {
 	s.merges = make(chan *segmentMerge)
 	s.introducerNotifier = make(chan *epochWatcher, 1)
 	s.revertToSnapshots = make(chan *snapshotReversion)
-	s.persisterNotifier = make(chan notificationChan)
+	s.persisterNotifier = make(chan *epochWatcher, 1)
 
 	if !s.readOnly && s.path != "" {
 		err := s.removeOldZapFiles() // Before persister or merger create any new files.
 		}
 	}
 
-	s.asyncTasks.Add(1)
-	go s.mainLoop()
-
-	if !s.readOnly && s.path != "" {
-		s.asyncTasks.Add(1)
-		go s.persisterLoop()
-		s.asyncTasks.Add(1)
-		go s.mergerLoop()
-	}
-
 	return nil
 }
 
 		introduction.persisted = make(chan error, 1)
 	}
 
-	// get read lock, to optimistically prepare obsoleted info
+	// optimistically prepare obsoletes outside of rootLock
 	s.rootLock.RLock()
-	for _, seg := range s.root.segment {
+	root := s.root
+	root.AddRef()
+	s.rootLock.RUnlock()
+
+	for _, seg := range root.segment {
 		delta, err := seg.segment.DocNumbers(ids)
 		if err != nil {
-			s.rootLock.RUnlock()
 			return err
 		}
 		introduction.obsoletes[seg.id] = delta
 	}
-	s.rootLock.RUnlock()
+
+	_ = root.DecRef()
 
 	s.introductions <- introduction
 

vendor/github.com/blevesearch/bleve/index/scorch/segment/mem/build.go

 	var numTokenFrequencies int
 	var totLocs int
 
+	// initial scan for all fieldID's to sort them
+	for _, result := range results {
+		for _, field := range result.Document.CompositeFields {
+			s.getOrDefineField(field.Name())
+		}
+		for _, field := range result.Document.Fields {
+			s.getOrDefineField(field.Name())
+		}
+	}
+	sort.Strings(s.FieldsInv[1:]) // keep _id as first field
+	s.FieldsMap = make(map[string]uint16, len(s.FieldsInv))
+	for fieldID, fieldName := range s.FieldsInv {
+		s.FieldsMap[fieldName] = uint16(fieldID + 1)
+	}
+
 	processField := func(fieldID uint16, tfs analysis.TokenFrequencies) {
 		for term, tf := range tfs {
 			pidPlus1, exists := s.Dicts[fieldID][term]

vendor/github.com/blevesearch/bleve/index/scorch/segment/mem/dict.go

 	prefix string
 	end    string
 	offset int
+
+	dictEntry index.DictEntry // reused across Next()'s
 }
 
 // Next returns the next entry in the dictionary
 
 	d.offset++
 	postingID := d.d.segment.Dicts[d.d.fieldID][next]
-	return &index.DictEntry{
-		Term:  next,
-		Count: d.d.segment.Postings[postingID-1].GetCardinality(),
-	}, nil
+	d.dictEntry.Term = next
+	d.dictEntry.Count = d.d.segment.Postings[postingID-1].GetCardinality()
+	return &d.dictEntry, nil
 }

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/build.go

 	"github.com/golang/snappy"
 )
 
-const version uint32 = 2
+const version uint32 = 3
 
 const fieldNotUninverted = math.MaxUint64
 
 }
 
 func persistStored(memSegment *mem.Segment, w *CountHashWriter) (uint64, error) {
-
 	var curr int
 	var metaBuf bytes.Buffer
 	var data, compressed []byte
 
+	metaEncoder := govarint.NewU64Base128Encoder(&metaBuf)
+
 	docNumOffsets := make(map[int]uint64, len(memSegment.Stored))
 
 	for docNum, storedValues := range memSegment.Stored {
 		if docNum != 0 {
 			// reset buffer if necessary
+			curr = 0
 			metaBuf.Reset()
 			data = data[:0]
 			compressed = compressed[:0]
-			curr = 0
 		}
 
-		metaEncoder := govarint.NewU64Base128Encoder(&metaBuf)
-
 		st := memSegment.StoredTypes[docNum]
 		sp := memSegment.StoredPos[docNum]
 
 		// encode fields in order
 		for fieldID := range memSegment.FieldsInv {
 			if storedFieldValues, ok := storedValues[uint16(fieldID)]; ok {
-				// has stored values for this field
-				num := len(storedFieldValues)
-
 				stf := st[uint16(fieldID)]
 				spf := sp[uint16(fieldID)]
 
-				// process each value
-				for i := 0; i < num; i++ {
-					// encode field
-					_, err2 := metaEncoder.PutU64(uint64(fieldID))
-					if err2 != nil {
-						return 0, err2
-					}
-					// encode type
-					_, err2 = metaEncoder.PutU64(uint64(stf[i]))
-					if err2 != nil {
-						return 0, err2
-					}
-					// encode start offset
-					_, err2 = metaEncoder.PutU64(uint64(curr))
-					if err2 != nil {
-						return 0, err2
-					}
-					// end len
-					_, err2 = metaEncoder.PutU64(uint64(len(storedFieldValues[i])))
-					if err2 != nil {
-						return 0, err2
-					}
-					// encode number of array pos
-					_, err2 = metaEncoder.PutU64(uint64(len(spf[i])))
-					if err2 != nil {
-						return 0, err2
-					}
-					// encode all array positions
-					for _, pos := range spf[i] {
-						_, err2 = metaEncoder.PutU64(pos)
-						if err2 != nil {
-							return 0, err2
-						}
-					}
-					// append data
-					data = append(data, storedFieldValues[i]...)
-					// update curr
-					curr += len(storedFieldValues[i])
+				var err2 error
+				curr, data, err2 = persistStoredFieldValues(fieldID,
+					storedFieldValues, stf, spf, curr, metaEncoder, data)
+				if err2 != nil {
+					return 0, err2
 				}
 			}
 		}
-		metaEncoder.Close()
 
+		metaEncoder.Close()
 		metaBytes := metaBuf.Bytes()
 
 		// compress the data
 	return rv, nil
 }
 
+func persistStoredFieldValues(fieldID int,
+	storedFieldValues [][]byte, stf []byte, spf [][]uint64,
+	curr int, metaEncoder *govarint.Base128Encoder, data []byte) (
+	int, []byte, error) {
+	for i := 0; i < len(storedFieldValues); i++ {
+		// encode field
+		_, err := metaEncoder.PutU64(uint64(fieldID))
+		if err != nil {
+			return 0, nil, err
+		}
+		// encode type
+		_, err = metaEncoder.PutU64(uint64(stf[i]))
+		if err != nil {
+			return 0, nil, err
+		}
+		// encode start offset
+		_, err = metaEncoder.PutU64(uint64(curr))
+		if err != nil {
+			return 0, nil, err
+		}
+		// end len
+		_, err = metaEncoder.PutU64(uint64(len(storedFieldValues[i])))
+		if err != nil {
+			return 0, nil, err
+		}
+		// encode number of array pos
+		_, err = metaEncoder.PutU64(uint64(len(spf[i])))
+		if err != nil {
+			return 0, nil, err
+		}
+		// encode all array positions
+		for _, pos := range spf[i] {
+			_, err = metaEncoder.PutU64(pos)
+			if err != nil {
+				return 0, nil, err
+			}
+		}
+
+		data = append(data, storedFieldValues[i]...)
+		curr += len(storedFieldValues[i])
+	}
+
+	return curr, data, nil
+}
+
 func persistPostingDetails(memSegment *mem.Segment, w *CountHashWriter, chunkFactor uint32) ([]uint64, []uint64, error) {
 	var freqOffsets, locOfffsets []uint64
 	tfEncoder := newChunkedIntCoder(uint64(chunkFactor), uint64(len(memSegment.Stored)-1))
 		if err != nil {
 			return nil, err
 		}
-		// resetting encoder for the next field
+		// reseting encoder for the next field
 		fdvEncoder.Reset()
 	}
 
 		return nil, err
 	}
 
+	return InitSegmentBase(br.Bytes(), cr.Sum32(), chunkFactor,
+		memSegment.FieldsMap, memSegment.FieldsInv, numDocs,
+		storedIndexOffset, fieldsIndexOffset, docValueOffset, dictLocs)
+}
+
+func InitSegmentBase(mem []byte, memCRC uint32, chunkFactor uint32,
+	fieldsMap map[string]uint16, fieldsInv []string, numDocs uint64,
+	storedIndexOffset uint64, fieldsIndexOffset uint64, docValueOffset uint64,
+	dictLocs []uint64) (*SegmentBase, error) {
 	sb := &SegmentBase{
-		mem:               br.Bytes(),
-		memCRC:            cr.Sum32(),
+		mem:               mem,
+		memCRC:            memCRC,
 		chunkFactor:       chunkFactor,
-		fieldsMap:         memSegment.FieldsMap,
-		fieldsInv:         memSegment.FieldsInv,
+		fieldsMap:         fieldsMap,
+		fieldsInv:         fieldsInv,
 		numDocs:           numDocs,
 		storedIndexOffset: storedIndexOffset,
 		fieldsIndexOffset: fieldsIndexOffset,
 		fieldDvIterMap:    make(map[uint16]*docValueIterator),
 	}
 
-	err = sb.loadDvIterators()
+	err := sb.loadDvIterators()
 	if err != nil {
 		return nil, err
 	}

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/contentcoder.go

 // MetaData represents the data information inside a
 // chunk.
 type MetaData struct {
-	DocID    uint64 // docid of the data inside the chunk
+	DocNum   uint64 // docNum of the data inside the chunk
 	DocDvLoc uint64 // starting offset for a given docid
 	DocDvLen uint64 // length of data inside the chunk for the given docid
 }
 	rv := &chunkedContentCoder{
 		chunkSize: chunkSize,
 		chunkLens: make([]uint64, total),
-		chunkMeta: []MetaData{},
+		chunkMeta: make([]MetaData, 0, total),
 	}
 
 	return rv
 	for i := range c.chunkLens {
 		c.chunkLens[i] = 0
 	}
-	c.chunkMeta = []MetaData{}
+	c.chunkMeta = c.chunkMeta[:0]
 }
 
 // Close indicates you are done calling Add() this allows
 
 	// write out the metaData slice
 	for _, meta := range c.chunkMeta {
-		_, err := writeUvarints(&c.chunkMetaBuf, meta.DocID, meta.DocDvLoc, meta.DocDvLen)
+		_, err := writeUvarints(&c.chunkMetaBuf, meta.DocNum, meta.DocDvLoc, meta.DocDvLen)
 		if err != nil {
 			return err
 		}
 		// clearing the chunk specific meta for next chunk
 		c.chunkBuf.Reset()
 		c.chunkMetaBuf.Reset()
-		c.chunkMeta = []MetaData{}
+		c.chunkMeta = c.chunkMeta[:0]
 		c.currChunk = chunk
 	}
 
 	}
 
 	c.chunkMeta = append(c.chunkMeta, MetaData{
-		DocID:    docNum,
+		DocNum:   docNum,
 		DocDvLoc: uint64(dvOffset),
 		DocDvLen: uint64(dvSize),
 	})

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/dict.go

 
 // PostingsList returns the postings list for the specified term
 func (d *Dictionary) PostingsList(term string, except *roaring.Bitmap) (segment.PostingsList, error) {
-	return d.postingsList([]byte(term), except)
+	return d.postingsList([]byte(term), except, nil)
 }
 
-func (d *Dictionary) postingsList(term []byte, except *roaring.Bitmap) (*PostingsList, error) {
-	rv := &PostingsList{
-		sb:     d.sb,
-		term:   term,
-		except: except,
+func (d *Dictionary) postingsList(term []byte, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
+	if d.fst == nil {
+		return d.postingsListInit(rv, except), nil
 	}
 
-	if d.fst != nil {
-		postingsOffset, exists, err := d.fst.Get(term)
-		if err != nil {
-			return nil, fmt.Errorf("vellum err: %v", err)
-		}
-		if exists {
-			err = rv.read(postingsOffset, d)
-			if err != nil {
-				return nil, err
-			}
-		}
+	postingsOffset, exists, err := d.fst.Get(term)
+	if err != nil {
+		return nil, fmt.Errorf("vellum err: %v", err)
+	}
+	if !exists {
+		return d.postingsListInit(rv, except), nil
+	}
+
+	return d.postingsListFromOffset(postingsOffset, except, rv)
+}
+
+func (d *Dictionary) postingsListFromOffset(postingsOffset uint64, except *roaring.Bitmap, rv *PostingsList) (*PostingsList, error) {
+	rv = d.postingsListInit(rv, except)
+
+	err := rv.read(postingsOffset, d)
+	if err != nil {
+		return nil, err
 	}
 
 	return rv, nil
 }
 
+func (d *Dictionary) postingsListInit(rv *PostingsList, except *roaring.Bitmap) *PostingsList {
+	if rv == nil {
+		rv = &PostingsList{}
+	} else {
+		*rv = PostingsList{} // clear the struct
+	}
+	rv.sb = d.sb
+	rv.except = except
+	return rv
+}
+
 // Iterator returns an iterator for this dictionary
 func (d *Dictionary) Iterator() segment.DictionaryIterator {
 	rv := &DictionaryIterator{

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/docvalues.go

 func (di *docValueIterator) loadDvChunk(chunkNumber,
 	localDocNum uint64, s *SegmentBase) error {
 	// advance to the chunk where the docValues
-	// reside for the given docID
+	// reside for the given docNum
 	destChunkDataLoc := di.dvDataLoc
 	for i := 0; i < int(chunkNumber); i++ {
 		destChunkDataLoc += di.chunkLens[i]
 	offset := uint64(0)
 	di.curChunkHeader = make([]MetaData, int(numDocs))
 	for i := 0; i < int(numDocs); i++ {
-		di.curChunkHeader[i].DocID, read = binary.Uvarint(s.mem[chunkMetaLoc+offset : chunkMetaLoc+offset+binary.MaxVarintLen64])
+		di.curChunkHeader[i].DocNum, read = binary.Uvarint(s.mem[chunkMetaLoc+offset : chunkMetaLoc+offset+binary.MaxVarintLen64])
 		offset += uint64(read)
 		di.curChunkHeader[i].DocDvLoc, read = binary.Uvarint(s.mem[chunkMetaLoc+offset : chunkMetaLoc+offset+binary.MaxVarintLen64])
 		offset += uint64(read)
 	return nil
 }
 
-func (di *docValueIterator) visitDocValues(docID uint64,
+func (di *docValueIterator) visitDocValues(docNum uint64,
 	visitor index.DocumentFieldTermVisitor) error {
-	// binary search the term locations for the docID
-	start, length := di.getDocValueLocs(docID)
+	// binary search the term locations for the docNum
+	start, length := di.getDocValueLocs(docNum)
 	if start == math.MaxUint64 || length == math.MaxUint64 {
 		return nil
 	}
 		return err
 	}
 
-	// pick the terms for the given docID
+	// pick the terms for the given docNum
 	uncompressed = uncompressed[start : start+length]
 	for {
 		i := bytes.Index(uncompressed, termSeparatorSplitSlice)
 	return nil
 }
 
-func (di *docValueIterator) getDocValueLocs(docID uint64) (uint64, uint64) {
+func (di *docValueIterator) getDocValueLocs(docNum uint64) (uint64, uint64) {
 	i := sort.Search(len(di.curChunkHeader), func(i int) bool {
-		return di.curChunkHeader[i].DocID >= docID
+		return di.curChunkHeader[i].DocNum >= docNum
 	})
-	if i < len(di.curChunkHeader) && di.curChunkHeader[i].DocID == docID {
+	if i < len(di.curChunkHeader) && di.curChunkHeader[i].DocNum == docNum {
 		return di.curChunkHeader[i].DocDvLoc, di.curChunkHeader[i].DocDvLen
 	}
 	return math.MaxUint64, math.MaxUint64

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/enumerator.go

+//  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 zap
+
+import (
+	"bytes"
+
+	"github.com/couchbase/vellum"
+)
+
+// enumerator provides an ordered traversal of multiple vellum
+// iterators.  Like JOIN of iterators, the enumerator produces a
+// sequence of (key, iteratorIndex, value) tuples, sorted by key ASC,
+// then iteratorIndex ASC, where the same key might be seen or
+// repeated across multiple child iterators.
+type enumerator struct {
+	itrs   []vellum.Iterator
+	currKs [][]byte
+	currVs []uint64
+
+	lowK    []byte
+	lowIdxs []int
+	lowCurr int
+}
+
+// newEnumerator returns a new enumerator over the vellum Iterators
+func newEnumerator(itrs []vellum.Iterator) (*enumerator, error) {
+	rv := &enumerator{
+		itrs:    itrs,
+		currKs:  make([][]byte, len(itrs)),
+		currVs:  make([]uint64, len(itrs)),
+		lowIdxs: make([]int, 0, len(itrs)),
+	}
+	for i, itr := range rv.itrs {
+		rv.currKs[i], rv.currVs[i] = itr.Current()
+	}
+	rv.updateMatches()
+	if rv.lowK == nil {
+		return rv, vellum.ErrIteratorDone
+	}
+	return rv, nil
+}
+
+// updateMatches maintains the low key matches based on the currKs
+func (m *enumerator) updateMatches() {
+	m.lowK = nil
+	m.lowIdxs = m.lowIdxs[:0]
+	m.lowCurr = 0
+
+	for i, key := range m.currKs {
+		if key == nil {
+			continue
+		}
+
+		cmp := bytes.Compare(key, m.lowK)
+		if cmp < 0 || m.lowK == nil {
+			// reached a new low
+			m.lowK = key
+			m.lowIdxs = m.lowIdxs[:0]
+			m.lowIdxs = append(m.lowIdxs, i)
+		} else if cmp == 0 {
+			m.lowIdxs = append(m.lowIdxs, i)
+		}
+	}
+}
+
+// Current returns the enumerator's current key, iterator-index, and
+// value.  If the enumerator is not pointing at a valid value (because
+// Next returned an error previously), Current will return nil,0,0.
+func (m *enumerator) Current() ([]byte, int, uint64) {
+	var i int
+	var v uint64
+	if m.lowCurr < len(m.lowIdxs) {
+		i = m.lowIdxs[m.lowCurr]
+		v = m.currVs[i]
+	}
+	return m.lowK, i, v
+}
+
+// Next advances the enumerator to the next key/iterator/value result,
+// else vellum.ErrIteratorDone is returned.
+func (m *enumerator) Next() error {
+	m.lowCurr += 1
+	if m.lowCurr >= len(m.lowIdxs) {
+		// move all the current low iterators forwards
+		for _, vi := range m.lowIdxs {
+			err := m.itrs[vi].Next()
+			if err != nil && err != vellum.ErrIteratorDone {
+				return err
+			}
+			m.currKs[vi], m.currVs[vi] = m.itrs[vi].Current()
+		}
+		m.updateMatches()
+	}
+	if m.lowK == nil {
+		return vellum.ErrIteratorDone
+	}
+	return nil
+}
+
+// Close all the underlying Iterators.  The first error, if any, will
+// be returned.
+func (m *enumerator) Close() error {
+	var rv error
+	for _, itr := range m.itrs {
+		err := itr.Close()
+		if rv == nil {
+			rv = err
+		}
+	}
+	return rv
+}

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/intcoder.go

 	encoder   *govarint.Base128Encoder
 	chunkLens []uint64
 	currChunk uint64
+
+	buf []byte
 }
 
 // newChunkedIntCoder returns a new chunk int coder which packs data into
 		// starting a new chunk
 		if c.encoder != nil {
 			// close out last
-			c.encoder.Close()
-			encodingBytes := c.chunkBuf.Bytes()
-			c.chunkLens[c.currChunk] = uint64(len(encodingBytes))
-			c.final = append(c.final, encodingBytes...)
+			c.Close()
 			c.chunkBuf.Reset()
-			c.encoder = govarint.NewU64Base128Encoder(&c.chunkBuf)
 		}
 		c.currChunk = chunk
 	}
 
 // Write commits all the encoded chunked integers to the provided writer.
 func (c *chunkedIntCoder) Write(w io.Writer) (int, error) {
-	var tw int
-	buf := make([]byte, binary.MaxVarintLen64)
-	// write out the number of chunks
+	bufNeeded := binary.MaxVarintLen64 * (1 + len(c.chunkLens))
+	if len(c.buf) < bufNeeded {
+		c.buf = make([]byte, bufNeeded)
+	}
+	buf := c.buf
+
+	// write out the number of chunks & each chunkLen
 	n := binary.PutUvarint(buf, uint64(len(c.chunkLens)))
-	nw, err := w.Write(buf[:n])
-	tw += nw
+	for _, chunkLen := range c.chunkLens {
+		n += binary.PutUvarint(buf[n:], uint64(chunkLen))
+	}
+
+	tw, err := w.Write(buf[:n])
 	if err != nil {
 		return tw, err
 	}
-	// write out the chunk lens
-	for _, chunkLen := range c.chunkLens {
-		n := binary.PutUvarint(buf, uint64(chunkLen))
-		nw, err = w.Write(buf[:n])
-		tw += nw
-		if err != nil {
-			return tw, err
-		}
-	}
+
 	// write out the data
-	nw, err = w.Write(c.final)
+	nw, err := w.Write(c.final)
 	tw += nw
 	if err != nil {
 		return tw, err

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/merge.go

 	"fmt"
 	"math"
 	"os"
+	"sort"
 
 	"github.com/RoaringBitmap/roaring"
 	"github.com/Smerity/govarint"
 	"github.com/golang/snappy"
 )
 
+const docDropped = math.MaxUint64 // sentinel docNum to represent a deleted doc
+
 // Merge takes a slice of zap segments and bit masks describing which
 // documents may be dropped, and creates a new segment containing the
 // remaining data.  This new segment is built at the specified path,
 		_ = os.Remove(path)
 	}
 
+	segmentBases := make([]*SegmentBase, len(segments))
+	for segmenti, segment := range segments {
+		segmentBases[segmenti] = &segment.SegmentBase
+	}
+
 	// buffer the output
 	br := bufio.NewWriter(f)
 
 	// wrap it for counting (tracking offsets)
 	cr := NewCountHashWriter(br)
 
-	fieldsInv := mergeFields(segments)
-	fieldsMap := mapFields(fieldsInv)
-
-	var newDocNums [][]uint64
-	var storedIndexOffset uint64
-	fieldDvLocsOffset := uint64(fieldNotUninverted)
-	var dictLocs []uint64
-
-	newSegDocCount := computeNewDocCount(segments, drops)
-	if newSegDocCount > 0 {
-		storedIndexOffset, newDocNums, err = mergeStoredAndRemap(segments, drops,
-			fieldsMap, fieldsInv, newSegDocCount, cr)
-		if err != nil {
-			cleanup()
-			return nil, err
-		}
-
-		dictLocs, fieldDvLocsOffset, err = persistMergedRest(segments, drops, fieldsInv, fieldsMap,
-			newDocNums, newSegDocCount, chunkFactor, cr)
-		if err != nil {
-			cleanup()
-			return nil, err
-		}
-	} else {
-		dictLocs = make([]uint64, len(fieldsInv))
-	}
-
-	fieldsIndexOffset, err := persistFields(fieldsInv, cr, dictLocs)
+	newDocNums, numDocs, storedIndexOffset, fieldsIndexOffset, docValueOffset, _, _, _, err :=
+		MergeToWriter(segmentBases, drops, chunkFactor, cr)
 	if err != nil {
 		cleanup()
 		return nil, err
 	}
 
-	err = persistFooter(newSegDocCount, storedIndexOffset,
-		fieldsIndexOffset, fieldDvLocsOffset, chunkFactor, cr.Sum32(), cr)
+	err = persistFooter(numDocs, storedIndexOffset, fieldsIndexOffset,
+		docValueOffset, chunkFactor, cr.Sum32(), cr)
 	if err != nil {
 		cleanup()
 		return nil, err
 	return newDocNums, nil
 }
 
-// mapFields takes the fieldsInv list and builds the map
+func MergeToWriter(segments []*SegmentBase, drops []*roaring.Bitmap,
+	chunkFactor uint32, cr *CountHashWriter) (
+	newDocNums [][]uint64,
+	numDocs, storedIndexOffset, fieldsIndexOffset, docValueOffset uint64,
+	dictLocs []uint64, fieldsInv []string, fieldsMap map[string]uint16,
+	err error) {
+	docValueOffset = uint64(fieldNotUninverted)
+
+	var fieldsSame bool
+	fieldsSame, fieldsInv = mergeFields(segments)
+	fieldsMap = mapFields(fieldsInv)
+
+	numDocs = computeNewDocCount(segments, drops)
+	if numDocs > 0 {
+		storedIndexOffset, newDocNums, err = mergeStoredAndRemap(segments, drops,
+			fieldsMap, fieldsInv, fieldsSame, numDocs, cr)
+		if err != nil {
+			return nil, 0, 0, 0, 0, nil, nil, nil, err
+		}
+
+		dictLocs, docValueOffset, err = persistMergedRest(segments, drops, fieldsInv, fieldsMap,
+			newDocNums, numDocs, chunkFactor, cr)
+		if err != nil {
+			return nil, 0, 0, 0, 0, nil, nil, nil, err
+		}
+	} else {
+		dictLocs = make([]uint64, len(fieldsInv))
+	}
+
+	fieldsIndexOffset, err = persistFields(fieldsInv, cr, dictLocs)
+	if err != nil {
+		return nil, 0, 0, 0, 0, nil, nil, nil, err
+	}
+
+	return newDocNums, numDocs, storedIndexOffset, fieldsIndexOffset, docValueOffset, dictLocs, fieldsInv, fieldsMap, nil
+}
+
+// mapFields takes the fieldsInv list and returns a map of fieldName
+// to fieldID+1
 func mapFields(fields []string) map[string]uint16 {
 	rv := make(map[string]uint16, len(fields))
 	for i, fieldName := range fields {
-		rv[fieldName] = uint16(i)
+		rv[fieldName] = uint16(i) + 1
 	}
 	return rv
 }
 
 // computeNewDocCount determines how many documents will be in the newly
 // merged segment when obsoleted docs are dropped
-func computeNewDocCount(segments []*Segment, drops []*roaring.Bitmap) uint64 {
+func computeNewDocCount(segments []*SegmentBase, drops []*roaring.Bitmap) uint64 {
 	var newDocCount uint64
 	for segI, segment := range segments {
-		newDocCount += segment.NumDocs()
+		newDocCount += segment.numDocs
 		if drops[segI] != nil {
 			newDocCount -= drops[segI].GetCardinality()
 		}
 	return newDocCount
 }
 
-func persistMergedRest(segments []*Segment, drops []*roaring.Bitmap,
-	fieldsInv []string, fieldsMap map[string]uint16, newDocNums [][]uint64,
+func persistMergedRest(segments []*SegmentBase, dropsIn []*roaring.Bitmap,
+	fieldsInv []string, fieldsMap map[string]uint16, newDocNumsIn [][]uint64,
 	newSegDocCount uint64, chunkFactor uint32,
 	w *CountHashWriter) ([]uint64, uint64, error) {
 
 	var bufMaxVarintLen64 []byte = make([]byte, binary.MaxVarintLen64)
 	var bufLoc []uint64
 
+	var postings *PostingsList
+	var postItr *PostingsIterator
+
 	rv := make([]uint64, len(fieldsInv))
 	fieldDvLocs := make([]uint64, len(fieldsInv))
-	fieldDvLocsOffset := uint64(fieldNotUninverted)
+
+	tfEncoder := newChunkedIntCoder(uint64(chunkFactor), newSegDocCount-1)
+	locEncoder := newChunkedIntCoder(uint64(chunkFactor), newSegDocCount-1)
 
 	// docTermMap is keyed by docNum, where the array impl provides
 	// better memory usage behavior than a sparse-friendlier hashmap
 			return nil, 0, err
 		}
 
-		// collect FST iterators from all segments for this field
+		// collect FST iterators from all active segments for this field
+		var newDocNums [][]uint64
+		var drops []*roaring.Bitmap
 		var dicts []*Dictionary
 		var itrs []vellum.Iterator
-		for _, segment := range segments {
+
+		for segmentI, segment := range segments {
 			dict, err2 := segment.dictionary(fieldName)
 			if err2 != nil {
 				return nil, 0, err2
 			}
-			dicts = append(dicts, dict)
-
 			if dict != nil && dict.fst != nil {
 				itr, err2 := dict.fst.Iterator(nil, nil)
 				if err2 != nil && err2 != vellum.ErrIteratorDone {
 					return nil, 0, err2
 				}
 				if itr != nil {
+					newDocNums = append(newDocNums, newDocNumsIn[segmentI])
+					drops = append(drops, dropsIn[segmentI])
+					dicts = append(dicts, dict)
 					itrs = append(itrs, itr)
 				}
 			}
 		}
 
-		// create merging iterator
-		mergeItr, err := vellum.NewMergeIterator(itrs, func(postingOffsets []uint64) uint64 {
-			// we don't actually use the merged value
-			return 0
-		})
-
-		tfEncoder := newChunkedIntCoder(uint64(chunkFactor), newSegDocCount-1)
-		locEncoder := newChunkedIntCoder(uint64(chunkFactor), newSegDocCount-1)
-
 		if uint64(cap(docTermMap)) < newSegDocCount {
 			docTermMap = make([][]byte, newSegDocCount)
 		} else {
 			}
 		}
 
-		for err == nil {
-			term, _ := mergeItr.Current()
-
-			newRoaring := roaring.NewBitmap()
-			newRoaringLocs := roaring.NewBitmap()
-
-			tfEncoder.Reset()
-			locEncoder.Reset()
-
-			// now go back and get posting list for this term
-			// but pass in the deleted docs for that segment
-			for dictI, dict := range dicts {
-				if dict == nil {
-					continue
-				}
-				postings, err2 := dict.postingsList(term, drops[dictI])
-				if err2 != nil {
-					return nil, 0, err2
-				}
-
-				postItr := postings.Iterator()
-				next, err2 := postItr.Next()
-				for next != nil && err2 == nil {
-					hitNewDocNum := newDocNums[dictI][next.Number()]
-					if hitNewDocNum == docDropped {
-						return nil, 0, fmt.Errorf("see hit with dropped doc num")
-					}
-					newRoaring.Add(uint32(hitNewDocNum))
-					// encode norm bits
-					norm := next.Norm()
-					normBits := math.Float32bits(float32(norm))
-					err = tfEncoder.Add(hitNewDocNum, next.Frequency(), uint64(normBits))
-					if err != nil {
-						return nil, 0, err
-					}
-					locs := next.Locations()
-					if len(locs) > 0 {
-						newRoaringLocs.Add(uint32(hitNewDocNum))
-						for _, loc := range locs {
-							if cap(bufLoc) < 5+len(loc.ArrayPositions()) {
-								bufLoc = make([]uint64, 0, 5+len(loc.ArrayPositions()))
-							}
-							args := bufLoc[0:5]
-							args[0] = uint64(fieldsMap[loc.Field()])
-							args[1] = loc.Pos()
-							args[2] = loc.Start()
-							args[3] = loc.End()
-							args[4] = uint64(len(loc.ArrayPositions()))
-							args = append(args, loc.ArrayPositions()...)
-							err = locEncoder.Add(hitNewDocNum, args...)
-							if err != nil {
-								return nil, 0, err
-							}
-						}
-					}
+		var prevTerm []byte
 
-					docTermMap[hitNewDocNum] =
-						append(append(docTermMap[hitNewDocNum], term...), termSeparator)
+		newRoaring := roaring.NewBitmap()
+		newRoaringLocs := roaring.NewBitmap()
 
-					next, err2 = postItr.Next()
-				}
-				if err2 != nil {
-					return nil, 0, err2
-				}
+		finishTerm := func(term []byte) error {
+			if term == nil {
+				return nil
 			}
 
 			tfEncoder.Close()
 			if newRoaring.GetCardinality() > 0 {
 				// this field/term actually has hits in the new segment, lets write it down
 				freqOffset := uint64(w.Count())
-				_, err = tfEncoder.Write(w)
+				_, err := tfEncoder.Write(w)
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
 				locOffset := uint64(w.Count())
 				_, err = locEncoder.Write(w)
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
 				postingLocOffset := uint64(w.Count())
 				_, err = writeRoaringWithLen(newRoaringLocs, w, &bufReuse, bufMaxVarintLen64)
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
 				postingOffset := uint64(w.Count())
+
 				// write out the start of the term info
-				buf := bufMaxVarintLen64
-				n := binary.PutUvarint(buf, freqOffset)
-				_, err = w.Write(buf[:n])
+				n := binary.PutUvarint(bufMaxVarintLen64, freqOffset)
+				_, err = w.Write(bufMaxVarintLen64[:n])
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
-
 				// write out the start of the loc info
-				n = binary.PutUvarint(buf, locOffset)
-				_, err = w.Write(buf[:n])
+				n = binary.PutUvarint(bufMaxVarintLen64, locOffset)
+				_, err = w.Write(bufMaxVarintLen64[:n])
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
-
-				// write out the start of the loc posting list
-				n = binary.PutUvarint(buf, postingLocOffset)
-				_, err = w.Write(buf[:n])
+				// write out the start of the posting locs
+				n = binary.PutUvarint(bufMaxVarintLen64, postingLocOffset)
+				_, err = w.Write(bufMaxVarintLen64[:n])
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
 				_, err = writeRoaringWithLen(newRoaring, w, &bufReuse, bufMaxVarintLen64)
 				if err != nil {
-					return nil, 0, err
+					return err
 				}
 
 				err = newVellum.Insert(term, postingOffset)
+				if err != nil {
+					return err
+				}
+			}
+
+			newRoaring = roaring.NewBitmap()
+			newRoaringLocs = roaring.NewBitmap()
+
+			tfEncoder.Reset()
+			locEncoder.Reset()
+
+			return nil
+		}
+
+		enumerator, err := newEnumerator(itrs)
+
+		for err == nil {
+			term, itrI, postingsOffset := enumerator.Current()
+
+			if !bytes.Equal(prevTerm, term) {
+				// if the term changed, write out the info collected
+				// for the previous term
+				err2 := finishTerm(prevTerm)
+				if err2 != nil {
+					return nil, 0, err2
+				}
+			}
+
+			var err2 error
+			postings, err2 = dicts[itrI].postingsListFromOffset(
+				postingsOffset, drops[itrI], postings)
+			if err2 != nil {
+				return nil, 0, err2
+			}
+
+			newDocNumsI := newDocNums[itrI]
+
+			postItr = postings.iterator(postItr)
+			next, err2 := postItr.Next()
+			for next != nil && err2 == nil {
+				hitNewDocNum := newDocNumsI[next.Number()]
+				if hitNewDocNum == docDropped {
+					return nil, 0, fmt.Errorf("see hit with dropped doc num")
+				}
+				newRoaring.Add(uint32(hitNewDocNum))
+				// encode norm bits
+				norm := next.Norm()
+				normBits := math.Float32bits(float32(norm))
+				err = tfEncoder.Add(hitNewDocNum, next.Frequency(), uint64(normBits))
 				if err != nil {
 					return nil, 0, err
 				}
+				locs := next.Locations()
+				if len(locs) > 0 {
+					newRoaringLocs.Add(uint32(hitNewDocNum))
+					for _, loc := range locs {
+						if cap(bufLoc) < 5+len(loc.ArrayPositions()) {
+							bufLoc = make([]uint64, 0, 5+len(loc.ArrayPositions()))
+						}
+						args := bufLoc[0:5]
+						args[0] = uint64(fieldsMap[loc.Field()] - 1)
+						args[1] = loc.Pos()
+						args[2] = loc.Start()
+						args[3] = loc.End()
+						args[4] = uint64(len(loc.ArrayPositions()))
+						args = append(args, loc.ArrayPositions()...)
+						err = locEncoder.Add(hitNewDocNum, args...)
+						if err != nil {
+							return nil, 0, err
+						}
+					}
+				}
+
+				docTermMap[hitNewDocNum] =
+					append(append(docTermMap[hitNewDocNum], term...), termSeparator)
+
+				next, err2 = postItr.Next()
+			}
+			if err2 != nil {
+				return nil, 0, err2
 			}
 
-			err = mergeItr.Next()
+			prevTerm = prevTerm[:0] // copy to prevTerm in case Next() reuses term mem
+			prevTerm = append(prevTerm, term...)
+
+			err = enumerator.Next()
 		}
 		if err != nil && err != vellum.ErrIteratorDone {
 			return nil, 0, err
 		}
 
+		err = finishTerm(prevTerm)
+		if err != nil {
+			return nil, 0, err
+		}
+
 		dictOffset := uint64(w.Count())
 
 		err = newVellum.Close()
 		}
 	}
 
-	fieldDvLocsOffset = uint64(w.Count())
+	fieldDvLocsOffset := uint64(w.Count())
 
 	buf := bufMaxVarintLen64
 	for _, offset := range fieldDvLocs {
 	return rv, fieldDvLocsOffset, nil
 }
 
-const docDropped = math.MaxUint64
-
-func mergeStoredAndRemap(segments []*Segment, drops []*roaring.Bitmap,
-	fieldsMap map[string]uint16, fieldsInv []string, newSegDocCount uint64,
+func mergeStoredAndRemap(segments []*SegmentBase, drops []*roaring.Bitmap,
+	fieldsMap map[string]uint16, fieldsInv []string, fieldsSame bool, newSegDocCount uint64,
 	w *CountHashWriter) (uint64, [][]uint64, error) {
 	var rv [][]uint64 // The remapped or newDocNums for each segment.
 
 	for segI, segment := range segments {
 		segNewDocNums := make([]uint64, segment.numDocs)
 
+		dropsI := drops[segI]
+
+		// optimize when the field mapping is the same across all
+		// segments and there are no deletions, via byte-copying
+		// of stored docs bytes directly to the writer
+		if fieldsSame && (dropsI == nil || dropsI.GetCardinality() == 0) {
+			err := segment.copyStoredDocs(newDocNum, docNumOffsets, w)
+			if err != nil {
+				return 0, nil, err
+			}
+
+			for i := uint64(0); i < segment.numDocs; i++ {
+				segNewDocNums[i] = newDocNum
+				newDocNum++
+			}
+			rv = append(rv, segNewDocNums)
+
+			continue
+		}
+
 		// for each doc num
 		for docNum := uint64(0); docNum < segment.numDocs; docNum++ {
 			// TODO: roaring's API limits docNums to 32-bits?
-			if drops[segI] != nil && drops[segI].Contains(uint32(docNum)) {
+			if dropsI != nil && dropsI.Contains(uint32(docNum)) {
 				segNewDocNums[docNum] = docDropped
 				continue
 			}
 				poss[i] = poss[i][:0]
 			}
 			err := segment.VisitDocument(docNum, func(field string, typ byte, value []byte, pos []uint64) bool {
-				fieldID := int(fieldsMap[field])
+				fieldID := int(fieldsMap[field]) - 1
 				vals[fieldID] = append(vals[fieldID], value)
 				typs[fieldID] = append(typs[fieldID], typ)
 				poss[fieldID] = append(poss[fieldID], pos)
 			for fieldID := range fieldsInv {
 				storedFieldValues := vals[int(fieldID)]
 
-				// has stored values for this field
-				num := len(storedFieldValues)
+				stf := typs[int(fieldID)]
+				spf := poss[int(fieldID)]
 
-				// process each value
-				for i := 0; i < num; i++ {
-					// encode field
-					_, err2 := metaEncoder.PutU64(uint64(fieldID))
-					if err2 != nil {
-						return 0, nil, err2
-					}
-					// encode type
-					_, err2 = metaEncoder.PutU64(uint64(typs[int(fieldID)][i]))
-					if err2 != nil {
-						return 0, nil, err2
-					}
-					// encode start offset
-					_, err2 = metaEncoder.PutU64(uint64(curr))
-					if err2 != nil {
-						return 0, nil, err2
-					}
-					// end len
-					_, err2 = metaEncoder.PutU64(uint64(len(storedFieldValues[i])))
-					if err2 != nil {
-						return 0, nil, err2
-					}
-					// encode number of array pos
-					_, err2 = metaEncoder.PutU64(uint64(len(poss[int(fieldID)][i])))
-					if err2 != nil {
-						return 0, nil, err2
-					}
-					// encode all array positions
-					for j := 0; j < len(poss[int(fieldID)][i]); j++ {
-						_, err2 = metaEncoder.PutU64(poss[int(fieldID)][i][j])
-						if err2 != nil {
-							return 0, nil, err2
-						}
-					}
-					// append data
-					data = append(data, storedFieldValues[i]...)
-					// update curr
-					curr += len(storedFieldValues[i])
+				var err2 error
+				curr, data, err2 = persistStoredFieldValues(fieldID,
+					storedFieldValues, stf, spf, curr, metaEncoder, data)
+				if err2 != nil {
+					return 0, nil, err2
 				}
 			}
 
 	}
 
 	// return value is the start of the stored index
-	offset := uint64(w.Count())
+	storedIndexOffset := uint64(w.Count())
 
 	// now write out the stored doc index
-	for docNum := range docNumOffsets {
-		err := binary.Write(w, binary.BigEndian, docNumOffsets[docNum])
+	for _, docNumOffset := range docNumOffsets {
+		err := binary.Write(w, binary.BigEndian, docNumOffset)
 		if err != nil {
 			return 0, nil, err
 		}
 	}
 
-	return offset, rv, nil
+	return storedIndexOffset, rv, nil
 }
 
-// mergeFields builds a unified list of fields used across all the input segments
-func mergeFields(segments []*Segment) []string {
-	fieldsMap := map[string]struct{}{}
+// copyStoredDocs writes out a segment's stored doc info, optimized by
+// using a single Write() call for the entire set of bytes.  The
+// newDocNumOffsets is filled with the new offsets for each doc.
+func (s *SegmentBase) copyStoredDocs(newDocNum uint64, newDocNumOffsets []uint64,
+	w *CountHashWriter) error {
+	if s.numDocs <= 0 {
+		return nil
+	}
+
+	indexOffset0, storedOffset0, _, _, _ :=
+		s.getDocStoredOffsets(0) // the segment's first doc
+
+	indexOffsetN, storedOffsetN, readN, metaLenN, dataLenN :=
+		s.getDocStoredOffsets(s.numDocs - 1) // the segment's last doc
+
+	storedOffset0New := uint64(w.Count())
+
+	storedBytes := s.mem[storedOffset0 : storedOffsetN+readN+metaLenN+dataLenN]
+	_, err := w.Write(storedBytes)
+	if err != nil {
+		return err
+	}
+
+	// remap the storedOffset's for the docs into new offsets relative
+	// to storedOffset0New, filling the given docNumOffsetsOut array
+	for indexOffset := indexOffset0; indexOffset <= indexOffsetN; indexOffset += 8 {
+		storedOffset := binary.BigEndian.Uint64(s.mem[indexOffset : indexOffset+8])
+		storedOffsetNew := storedOffset - storedOffset0 + storedOffset0New
+		newDocNumOffsets[newDocNum] = storedOffsetNew
+		newDocNum += 1
+	}
+
+	return nil
+}
+
+// mergeFields builds a unified list of fields used across all the
+// input segments, and computes whether the fields are the same across
+// segments (which depends on fields to be sorted in the same way
+// across segments)
+func mergeFields(segments []*SegmentBase) (bool, []string) {
+	fieldsSame := true
+
+	var segment0Fields []string
+	if len(segments) > 0 {
+		segment0Fields = segments[0].Fields()
+	}
+
+	fieldsExist := map[string]struct{}{}
 	for _, segment := range segments {
 		fields := segment.Fields()
-		for _, field := range fields {
-			fieldsMap[field] = struct{}{}
+		for fieldi, field := range fields {
+			fieldsExist[field] = struct{}{}
+			if len(segment0Fields) != len(fields) || segment0Fields[fieldi] != field {
+				fieldsSame = false
+			}
 		}
 	}
 
-	rv := make([]string, 0, len(fieldsMap))
+	rv := make([]string, 0, len(fieldsExist))
 	// ensure _id stays first
 	rv = append(rv, "_id")
-	for k := range fieldsMap {
+	for k := range fieldsExist {
 		if k != "_id" {
 			rv = append(rv, k)
 		}
 	}
-	return rv
+
+	sort.Strings(rv[1:]) // leave _id as first
+
+	return fieldsSame, rv
 }

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/posting.go

 // PostingsList is an in-memory represenation of a postings list
 type PostingsList struct {
 	sb             *SegmentBase
-	term           []byte
 	postingsOffset uint64
 	freqOffset     uint64
 	locOffset      uint64
 	locBitmap      *roaring.Bitmap
 	postings       *roaring.Bitmap
 	except         *roaring.Bitmap
-	postingKey     []byte
 }
 
 // Iterator returns an iterator for this postings list
 func (p *PostingsList) Iterator() segment.PostingsIterator {
-	rv := &PostingsIterator{
-		postings: p,
+	return p.iterator(nil)
+}
+
+func (p *PostingsList) iterator(rv *PostingsIterator) *PostingsIterator {
+	if rv == nil {
+		rv = &PostingsIterator{}
+	} else {
+		*rv = PostingsIterator{} // clear the struct
 	}
+	rv.postings = p
+
 	if p.postings != nil {
 		// prepare the freq chunk details
 		var n uint64

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/read.go

 import "encoding/binary"
 
 func (s *SegmentBase) getDocStoredMetaAndCompressed(docNum uint64) ([]byte, []byte) {
-	docStoredStartAddr := s.storedIndexOffset + (8 * docNum)
-	docStoredStart := binary.BigEndian.Uint64(s.mem[docStoredStartAddr : docStoredStartAddr+8])
+	_, storedOffset, n, metaLen, dataLen := s.getDocStoredOffsets(docNum)
+
+	meta := s.mem[storedOffset+n : storedOffset+n+metaLen]
+	data := s.mem[storedOffset+n+metaLen : storedOffset+n+metaLen+dataLen]
+
+	return meta, data
+}
+
+func (s *SegmentBase) getDocStoredOffsets(docNum uint64) (
+	uint64, uint64, uint64, uint64, uint64) {
+	indexOffset := s.storedIndexOffset + (8 * docNum)
+
+	storedOffset := binary.BigEndian.Uint64(s.mem[indexOffset : indexOffset+8])
+
 	var n uint64
-	metaLen, read := binary.Uvarint(s.mem[docStoredStart : docStoredStart+binary.MaxVarintLen64])
+
+	metaLen, read := binary.Uvarint(s.mem[storedOffset : storedOffset+binary.MaxVarintLen64])
 	n += uint64(read)
-	var dataLen uint64
-	dataLen, read = binary.Uvarint(s.mem[docStoredStart+n : docStoredStart+n+binary.MaxVarintLen64])
+
+	dataLen, read := binary.Uvarint(s.mem[storedOffset+n : storedOffset+n+binary.MaxVarintLen64])
 	n += uint64(read)
-	meta := s.mem[docStoredStart+n : docStoredStart+n+metaLen]
-	data := s.mem[docStoredStart+n+metaLen : docStoredStart+n+metaLen+dataLen]
-	return meta, data
+
+	return indexOffset, storedOffset, n, metaLen, dataLen
 }

vendor/github.com/blevesearch/bleve/index/scorch/segment/zap/segment.go

 			return nil, err
 		}
 
+		var postings *PostingsList
 		for _, id := range ids {
-			postings, err := idDict.postingsList([]byte(id), nil)
+			postings, err = idDict.postingsList([]byte(id), nil, postings)
 			if err != nil {
 				return nil, err
 			}

vendor/github.com/blevesearch/bleve/index/scorch/snapshot_rollback.go

 	return r.meta[string(key)]
 }
 
-// RollbackPoints returns an array of rollback points available
-// for the application to make a decision on where to rollback
-// to. A nil return value indicates that there are no available
-// rollback points.
+// RollbackPoints returns an array of rollback points available for
+// the application to rollback to, with more recent rollback points
+// (higher epochs) coming first.
 func (s *Scorch) RollbackPoints() ([]*RollbackPoint, error) {
 	if s.rootBolt == nil {
 		return nil, fmt.Errorf("RollbackPoints: root is nil")
 
 	snapshots := tx.Bucket(boltSnapshotsBucket)
 	if snapshots == nil {
-		return nil, fmt.Errorf("RollbackPoints: no snapshots available")
+		return nil, nil
 	}
 
 	rollbackPoints := []*RollbackPoint{}
 
 		revert.snapshot = indexSnapshot
 		revert.applied = make(chan error)
-
-		if !s.unsafeBatch {
-			revert.persisted = make(chan error)
-		}
+		revert.persisted = make(chan error)
 
 		return nil
 	})
 		return fmt.Errorf("Rollback: failed with err: %v", err)
 	}
 
-	if revert.persisted != nil {
-		err = <-revert.persisted
-	}
-
-	return err
+	return <-revert.persisted
 }

vendor/github.com/blevesearch/bleve/index/upsidedown/upsidedown.go

 			docBackIndexRowErr = err
 			return
 		}
+		defer func() {
+			if cerr := kvreader.Close(); err == nil && cerr != nil {
+				docBackIndexRowErr = cerr
+			}
+		}()
 
 		for docID, doc := range batch.IndexOps {
 			backIndexRow, err := backIndexRowForDoc(kvreader, index.IndexInternalID(docID))
 
 			docBackIndexRowCh <- &docBackIndexRow{docID, doc, backIndexRow}
 		}
-
-		err = kvreader.Close()
-		if err != nil {
-			docBackIndexRowErr = err
-			return
-		}
 	}()
 
 	// wait for analysis result

vendor/github.com/blevesearch/bleve/index_alias_impl.go

 package bleve
 
 import (
+	"context"
 	"sort"
 	"sync"
 	"time"
 
-	"golang.org/x/net/context"
-
 	"github.com/blevesearch/bleve/document"
 	"github.com/blevesearch/bleve/index"
 	"github.com/blevesearch/bleve/index/store"

vendor/github.com/blevesearch/bleve/index_impl.go

 package bleve
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"os"
 	"sync/atomic"
 	"time"
 
-	"golang.org/x/net/context"
-
 	"github.com/blevesearch/bleve/document"
 	"github.com/blevesearch/bleve/index"
 	"github.com/blevesearch/bleve/index/store"

vendor/github.com/blevesearch/bleve/search/collector.go

 package search
 
 import (
+	"context"
 	"time"
 
 	"github.com/blevesearch/bleve/index"
-
-	"golang.org/x/net/context"
 )
 
 type Collector interface {

vendor/github.com/blevesearch/bleve/search/collector/topn.go

 package collector
 
 import (
+	"context"
 	"time"
 
 	"github.com/blevesearch/bleve/index"
 	"github.com/blevesearch/bleve/search"
-	"golang.org/x/net/context"
 )
 
 type collectorStore interface {

vendor/github.com/markbates/goth/provider.go

 package goth
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 
-	"golang.org/x/net/context"
 	"golang.org/x/oauth2"
 )
 

vendor/github.com/markbates/goth/providers/facebook/facebook.go

 
 import (
 	"bytes"
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"net/http"
 	"net/url"
+	"strings"
 
-	"crypto/hmac"
-	"crypto/sha256"
-	"encoding/hex"
-	"fmt"
 	"github.com/markbates/goth"
 	"golang.org/x/oauth2"
 )
 const (
 	authURL         string = "https://www.facebook.com/dialog/oauth"
 	tokenURL        string = "https://graph.facebook.com/oauth/access_token"
-	endpointProfile string = "https://graph.facebook.com/me?fields=email,first_name,last_name,link,about,id,name,picture,location"
+	endpointProfile string = "https://graph.facebook.com/me?fields="
 )
 
 // New creates a new Facebook provider, and sets up important connection details.
 
 // BeginAuth asks Facebook for an authentication end-point.
 func (p *Provider) BeginAuth(state string) (goth.Session, error) {
-	url := p.config.AuthCodeURL(state)
+	authUrl := p.config.AuthCodeURL(state)
 	session := &Session{
-		AuthURL: url,
+		AuthURL: authUrl,
 	}
 	return session, nil
 }
 	hash.Write([]byte(sess.AccessToken))
 	appsecretProof := hex.EncodeToString(hash.Sum(nil))
 
-	response, err := p.Client().Get(endpointProfile + "&access_token=" + url.QueryEscape(sess.AccessToken) + "&appsecret_proof=" + appsecretProof)
+	reqUrl := fmt.Sprint(
+		endpointProfile,
+		strings.Join(p.config.Scopes, ","),
+		"&access_token=",
+		url.QueryEscape(sess.AccessToken),
+		"&appsecret_proof=",
+		appsecretProof,
+	)
+	response, err := p.Client().Get(reqUrl)
 	if err != nil {
 		return user, err
 	}
 		},
 		Scopes: []string{
 			"email",
+			"first_name",
+			"last_name",
+			"link",
+			"about",
+			"id",
+			"name",
+			"picture",
+			"location",
 		},
 	}
 
-	defaultScopes := map[string]struct{}{
-		"email": {},
-	}
-
-	for _, scope := range scopes {
-		if _, exists := defaultScopes[scope]; !exists {
-			c.Scopes = append(c.Scopes, scope)
+	// creates possibility to invoke field method like 'picture.type(large)'
+	var found bool
+	for _, sc := range scopes {
+		sc := sc
+		for i, defScope := range c.Scopes {
+			if defScope == strings.Split(sc, ".")[0] {
+				c.Scopes[i] = sc
+				found = true
+			}
+		}
+		if !found {
+			c.Scopes = append(c.Scopes, sc)
 		}
+		found = false
 	}
 
 	return c

vendor/golang.org/x/net/context/ctxhttp/ctxhttp.go

+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.7
+
+// Package ctxhttp provides helper functions for performing context-aware HTTP requests.
+package ctxhttp // import "golang.org/x/net/context/ctxhttp"
+
+import (
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"golang.org/x/net/context"
+)
+
+// Do sends an HTTP request with the provided http.Client and returns
+// an HTTP response.
+//
+// If the client is nil, http.DefaultClient is used.
+//
+// The provided ctx must be non-nil. If it is canceled or times out,
+// ctx.Err() will be returned.
+func Do(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) {
+	if client == nil {
+		client = http.DefaultClient
+	}
+	resp, err := client.Do(req.WithContext(ctx))
+	// If we got an error, and the context has been canceled,
+	// the context's error is probably more useful.
+	if err != nil {
+		select {
+		case <-ctx.Done():
+			err = ctx.Err()
+		default:
+		}
+	}
+	return resp, err
+}
+
+// Get issues a GET request via the Do function.
+func Get(ctx context.Context, client *http.Client, url string) (*http.Response, error) {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return Do(ctx, client, req)
+}
+
+// Head issues a HEAD request via the Do function.
+func Head(ctx context.Context, client *http.Client, url string) (*http.Response, error) {
+	req, err := http.NewRequest("HEAD", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return Do(ctx, client, req)
+}
+
+// Post issues a POST request via the Do function.
+func Post(ctx context.Context, client *http.Client, url string, bodyType string, body io.Reader) (*http.Response, error) {
+	req, err := http.NewRequest("POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", bodyType)
+	return Do(ctx, client, req)
+}
+
+// PostForm issues a POST request via the Do function.
+func PostForm(ctx context.Context, client *http.Client, url string, data url.Values) (*http.Response, error) {
+	return Post(ctx, client, url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
+}

vendor/golang.org/x/net/context/ctxhttp/ctxhttp_pre17.go

+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.7
+
+package ctxhttp // import "golang.org/x/net/context/ctxhttp"
+
+import (
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"golang.org/x/net/context"
+)
+
+func nop() {}
+
+var (
+	testHookContextDoneBeforeHeaders = nop
+	testHookDoReturned               = nop
+	testHookDidBodyClose             = nop
+)
+
+// Do sends an HTTP request with the provided http.Client and returns an HTTP response.
+// If the client is nil, http.DefaultClient is used.
+// If the context is canceled or times out, ctx.Err() will be returned.
+func Do(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) {
+	if client == nil {
+		client = http.DefaultClient
+	}
+
+	// TODO(djd): Respect any existing value of req.Cancel.
+	cancel := make(chan struct{})
+	req.Cancel = cancel
+
+	type responseAndError struct {
+		resp *http.Response
+		err  error
+	}
+	result := make(chan responseAndError, 1)
+
+	// Make local copies of test hooks closed over by goroutines below.
+	// Prevents data races in tests.
+	testHookDoReturned := testHookDoReturned
+	testHookDidBodyClose := testHookDidBodyClose
+
+	go func() {
+		resp, err := client.Do(req)
+		testHookDoReturned()
+		result <- responseAndError{resp, err}
+	}()
+
+	var resp *http.Response
+
+	select {
+	case <-ctx.Done():
+		testHookContextDoneBeforeHeaders()
+		close(cancel)
+		// Clean up after the goroutine calling client.Do:
+		go func() {
+			if r := <-result; r.resp != nil {
+				testHookDidBodyClose()
+				r.resp.Body.Close()
+			}
+		}()
+		return nil, ctx.Err()
+	case r := <-result:
+		var err error
+		resp, err = r.resp, r.err
+		if err != nil {
+			return resp, err
+		}
+	}
+
+	c := make(chan struct{})
+	go func() {
+		select {
+		case <-ctx.Done():
+			close(cancel)
+		case <-c:
+			// The response's Body is closed.
+		}
+	}()
+	resp.Body = &notifyingReader{resp.Body, c}
+
+	return resp, nil
+}
+
+// Get issues a GET request via the Do function.
+func Get(ctx context.Context, client *http.Client, url string) (*http.Response, error) {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return Do(ctx, client, req)
+}
+
+// Head issues a HEAD request via the Do function.
+func Head(ctx context.Context, client *http.Client, url string) (*http.Response, error) {
+	req, err := http.NewRequest("HEAD", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return Do(ctx, client, req)
+}
+
+// Post issues a POST request via the Do function.
+func Post(ctx context.Context, client *http.Client, url string, bodyType string, body io.Reader) (*http.Response, error) {
+	req, err := http.NewRequest("POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", bodyType)
+	return Do(ctx, client, req)
+}
+
+// PostForm issues a POST request via the Do function.
+func PostForm(ctx context.Context, client *http.Client, url string, data url.Values) (*http.Response, error) {
+	return Post(ctx, client, url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
+}
+
+// notifyingReader is an io.ReadCloser that closes the notify channel after
+// Close is called or a Read fails on the underlying ReadCloser.
+type notifyingReader struct {
+	io.ReadCloser
+	notify chan<- struct{}
+}
+
+func (r *notifyingReader) Read(p []byte) (int, error) {
+	n, err := r.ReadCloser.Read(p)
+	if err != nil && r.notify != nil {
+		close(r.notify)
+		r.notify = nil
+	}
+	return n, err
+}
+
+func (r *notifyingReader) Close() error {
+	err := r.ReadCloser.Close()
+	if r.notify != nil {
+		close(r.notify)
+		r.notify = nil
+	}
+	return err
+}

vendor/golang.org/x/oauth2/LICENSE

-Copyright (c) 2009 The oauth2 Authors. All rights reserved.
+Copyright (c) 2009 The Go Authors. All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are

vendor/golang.org/x/oauth2/client_appengine.go

-// Copyright 2014 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build appengine
-
-// App Engine hooks.
-
-package oauth2
-
-import (
-	"net/http"
-
-	"golang.org/x/net/context"
-	"golang.org/x/oauth2/internal"
-	"google.golang.org/appengine/urlfetch"
-)
-
-func init() {
-	internal.RegisterContextClientFunc(contextClientAppEngine)
-}
-
-func contextClientAppEngine(ctx context.Context) (*http.Client, error) {
-	return urlfetch.Client(ctx), nil
-}

vendor/golang.org/x/oauth2/internal/client_appengine.go

+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build appengine
+
+package internal
+
+import "google.golang.org/appengine/urlfetch"
+
+func init() {
+	appengineClientHook = urlfetch.Client
+}

vendor/golang.org/x/oauth2/internal/doc.go

+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package internal contains support packages for oauth2 package.
+package internal

vendor/golang.org/x/oauth2/internal/oauth2.go

 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package internal contains support packages for oauth2 package.
 package internal
 
 import (
-	"bufio"
 	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
 	"errors"
 	"fmt"
-	"io"
-	"strings"
 )
 
 // ParseKey converts the binary contents of a private key file
 	if err != nil {
 		parsedKey, err = x509.ParsePKCS1PrivateKey(key)
 		if err != nil {
-			return nil, fmt.Errorf("private key should be a PEM or plain PKSC1 or PKCS8; parse error: %v", err)
+			return nil, fmt.Errorf("private key should be a PEM or plain PKCS1 or PKCS8; parse error: %v", err)
 		}
 	}
 	parsed, ok := parsedKey.(*rsa.PrivateKey)
 	}
 	return parsed, nil
 }
-
-func ParseINI(ini io.Reader) (map[string]map[string]string, error) {
-	result := map[string]map[string]string{
-		"": map[string]string{}, // root section
-	}
-	scanner := bufio.NewScanner(ini)
-	currentSection := ""
-	for scanner.Scan() {
-		line := strings.TrimSpace(scanner.Text())
-		if strings.HasPrefix(line, ";") {
-			// comment.
-			continue
-		}
-		if strings.HasPrefix(line, "[") && strings.HasSuffix(line, "]") {
-			currentSection = strings.TrimSpace(line[1 : len(line)-1])
-			result[currentSection] = map[string]string{}
-			continue
-		}
-		parts := strings.SplitN(line, "=", 2)
-		if len(parts) == 2 && parts[0] != "" {
-			result[currentSection][strings.TrimSpace(parts[0])] = strings.TrimSpace(parts[1])
-		}
-	}
-	if err := scanner.Err(); err != nil {
-		return nil, fmt.Errorf("error scanning ini: %v", err)
-	}
-	return result, nil
-}
-
-func CondVal(v string) []string {
-	if v == "" {
-		return nil
-	}
-	return []string{v}
-}

vendor/golang.org/x/oauth2/internal/token.go

 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package internal contains support packages for oauth2 package.
 package internal
 
 import (
+	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"strings"
 	"time"
 
-	"golang.org/x/net/context"
+	"golang.org/x/net/context/ctxhttp"
 )
 
-// Token represents the crendentials used to authorize
+// Token represents the credentials used to authorize
 // the requests to access protected resources on the OAuth 2.0
 // provider's backend.
 //
 
 var brokenAuthHeaderProviders = []string{
 	"https://accounts.google.com/",
+	"https://api.codeswholesale.com/oauth/token",
 	"https://api.dropbox.com/",
 	"https://api.dropboxapi.com/",
 	"https://api.instagram.com/",
 	"https://api.pushbullet.com/",
 	"https://api.soundcloud.com/",
 	"https://api.twitch.tv/",
+	"https://id.twitch.tv/",
 	"https://app.box.com/",
+	"https://api.box.com/",
 	"https://connect.stripe.com/",
+	"https://login.mailchimp.com/",
 	"https://login.microsoftonline.com/",
 	"https://login.salesforce.com/",
+	"https://login.windows.net",
+	"https://login.live.com/",
+	"https://login.live-int.com/",
 	"https://oauth.sandbox.trainingpeaks.com/",
 	"https://oauth.trainingpeaks.com/",
 	"https://oauth.vk.com/",
 	"https://www.strava.com/oauth/",
 	"https://www.wunderlist.com/oauth/",
 	"https://api.patreon.com/",
+	"https://sandbox.codeswholesale.com/oauth/token",
+	"https://api.sipgate.com/v1/authorization/oauth",
+	"https://api.medium.com/v1/tokens",
+	"https://log.finalsurge.com/oauth/token",
+	"https://multisport.todaysplan.com.au/rest/oauth/access_token",
+	"https://whats.todaysplan.com.au/rest/oauth/access_token",
+	"https://stackoverflow.com/oauth/access_token",
+	"https://account.health.nokia.com",
+	"https://accounts.zoho.com",
+}
+
+// brokenAuthHeaderDomains lists broken providers that issue dynamic endpoints.
+var brokenAuthHeaderDomains = []string{
+	".auth0.com",
+	".force.com",
+	".myshopify.com",
+	".okta.com",
+	".oktapreview.com",
 }
 
 func RegisterBrokenAuthHeaderProvider(tokenURL string) {
 		}
 	}
 
+	if u, err := url.Parse(tokenURL); err == nil {
+		for _, s := range brokenAuthHeaderDomains {
+			if strings.HasSuffix(u.Host, s) {
+				return false
+			}
+		}
+	}
+
 	// Assume the provider implements the spec properly
 	// otherwise. We can add more exceptions as they're
 	// discovered. We will _not_ be adding configurable hooks
 }
 
 func RetrieveToken(ctx context.Context, clientID, clientSecret, tokenURL string, v url.Values) (*Token, error) {
-	hc, err := ContextClient(ctx)
-	if err != nil {
-		return nil, err
-	}
-	v.Set("client_id", clientID)
 	bustedAuth := !providerAuthHeaderWorks(tokenURL)
-	if bustedAuth && clientSecret != "" {
-		v.Set("client_secret", clientSecret)
+	if bustedAuth {
+		if clientID != "" {
+			v.Set("client_id", clientID)
+		}
+		if clientSecret != "" {
+			v.Set("client_secret", clientSecret)
+		}
 	}
 	req, err := http.NewRequest("POST", tokenURL, strings.NewReader(v.Encode()))
 	if err != nil {
 	}
 	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 	if !bustedAuth {
-		req.SetBasicAuth(clientID, clientSecret)
+		req.SetBasicAuth(url.QueryEscape(clientID), url.QueryEscape(clientSecret))
 	}
-	r, err := hc.Do(req)
+	r, err := ctxhttp.Do(ctx, ContextClient(ctx), req)
 	if err != nil {
 		return nil, err
 	}
 		return nil, fmt.Errorf("oauth2: cannot fetch token: %v", err)
 	}
 	if code := r.StatusCode; code < 200 || code > 299 {
-		return nil, fmt.Errorf("oauth2: cannot fetch token: %v\nResponse: %s", r.Status, body)
+		return nil, &RetrieveError{
+			Response: r,
+			Body:     body,
+		}
 	}
 
 	var token *Token
 	if token.RefreshToken == "" {
 		token.RefreshToken = v.Get("refresh_token")
 	}
+	if token.AccessToken == "" {
+		return token, errors.New("oauth2: server response missing access_token")
+	}
 	return token, nil
 }
+
+type RetrieveError struct {
+	Response *http.Response
+	Body     []byte
+}
+
+func (r *RetrieveError) Error() string {
+	return fmt.Sprintf("oauth2: cannot fetch token: %v\nResponse: %s", r.Response.Status, r.Body)
+}

vendor/golang.org/x/oauth2/internal/transport.go

 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package internal contains support packages for oauth2 package.
 package internal
 
 import (
+	"context"
 	"net/http"
-
-	"golang.org/x/net/context"
 )
 
 // HTTPClient is the context key to use with golang.org/x/net/context's
 // because nobody else can create a ContextKey, being unexported.
 type ContextKey struct{}
 
-// ContextClientFunc is a func which tries to return an *http.Client
-// given a Context value. If it returns an error, the search stops
-// with that error.  If it returns (nil, nil), the search continues
-// down the list of registered funcs.
-type ContextClientFunc func(context.Context) (*http.Client, error)
-
-var contextClientFuncs []ContextClientFunc
-
-func RegisterContextClientFunc(fn ContextClientFunc) {
-	contextClientFuncs = append(contextClientFuncs, fn)
-}
+var appengineClientHook func(context.Context) *http.Client
 
-func ContextClient(ctx context.Context) (*http.Client, error) {
+func ContextClient(ctx context.Context) *http.Client {
 	if ctx != nil {
 		if hc, ok := ctx.Value(HTTPClient).(*http.Client); ok {
-			return hc, nil
-		}
-	}
-	for _, fn := range contextClientFuncs {
-		c, err := fn(ctx)
-		if err != nil {
-			return nil, err
-		}
-		if c != nil {
-			return c, nil
+			return hc
 		}
 	}
-	return http.DefaultClient, nil
-}
-
-func ContextTransport(ctx context.Context) http.RoundTripper {
-	hc, err := ContextClient(ctx)
-	// This is a rare error case (somebody using nil on App Engine).
-	if err != nil {
-		return ErrorTransport{err}
+	if appengineClientHook != nil {
+		return appengineClientHook(ctx)
 	}
-	return hc.Transport
-}
-
-// ErrorTransport returns the specified error on RoundTrip.
-// This RoundTripper should be used in rare error cases where
-// error handling can be postponed to response handling time.
-type ErrorTransport struct{ Err error }
-
-func (t ErrorTransport) RoundTrip(*http.Request) (*http.Response, error) {
-	return nil, t.Err
+	return http.DefaultClient
 }

vendor/golang.org/x/oauth2/oauth2.go

 // license that can be found in the LICENSE file.
 
 // Package oauth2 provides support for making
-// OAuth2 authorized and authenticated HTTP requests.
+// OAuth2 authorized and authenticated HTTP requests,
+// as specified in RFC 6749.
 // It can additionally grant authorization with Bearer JWT.
 package oauth2 // import "golang.org/x/oauth2"
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"net/http"
 	"net/url"
 	"strings"
 	"sync"
 
-	"golang.org/x/net/context"
 	"golang.org/x/oauth2/internal"
 )
 
 // that asks for permissions for the required scopes explicitly.
 //
 // State is a token to protect the user from CSRF attacks. You must
-// always provide a non-zero string and validate that it matches the
+// always provide a non-empty string and validate that it matches the
 // the state query parameter on your redirect callback.
 // See http://tools.ietf.org/html/rfc6749#section-10.12 for more info.
 //
 // Opts may include AccessTypeOnline or AccessTypeOffline, as well
 // as ApprovalForce.
+// It can also be used to pass the PKCE challange.
+// See https://www.oauth.com/oauth2-servers/pkce/ for more info.
 func (c *Config) AuthCodeURL(state string, opts ...AuthCodeOption) string {
 	var buf bytes.Buffer
 	buf.WriteString(c.Endpoint.AuthURL)
 	v := url.Values{
 		"response_type": {"code"},
 		"client_id":     {c.ClientID},
-		"redirect_uri":  internal.CondVal(c.RedirectURL),
-		"scope":         internal.CondVal(strings.Join(c.Scopes, " ")),
-		"state":         internal.CondVal(state),
+	}
+	if c.RedirectURL != "" {
+		v.Set("redirect_uri", c.RedirectURL)
+	}
+	if len(c.Scopes) > 0 {
+		v.Set("scope", strings.Join(c.Scopes, " "))
+	}
+	if state != "" {
+		// TODO(light): Docs say never to omit state; don't allow empty.
+		v.Set("state", state)
 	}
 	for _, opt := range opts {
 		opt.setValue(v)
 // The HTTP client to use is derived from the context.
 // If nil, http.DefaultClient is used.
 func (c *Config) PasswordCredentialsToken(ctx context.Context, username, password string) (*Token, error) {
-	return retrieveToken(ctx, c, url.Values{
+	v := url.Values{
 		"grant_type": {"password"},
 		"username":   {username},
 		"password":   {password},
-		"scope":      internal.CondVal(strings.Join(c.Scopes, " ")),
-	})
+	}
+	if len(c.Scopes) > 0 {
+		v.Set("scope", strings.Join(c.Scopes, " "))
+	}
+	return retrieveToken(ctx, c, v)
 }
 
 // Exchange converts an authorization code into a token.
 //
 // The code will be in the *http.Request.FormValue("code"). Before
 // calling Exchange, be sure to validate FormValue("state").
-func (c *Config) Exchange(ctx context.Context, code string) (*Token, error) {
-	return retrieveToken(ctx, c, url.Values{
-		"grant_type":   {"authorization_code"},
-		"code":         {code},
-		"redirect_uri": internal.CondVal(c.RedirectURL),
-		"scope":        internal.CondVal(strings.Join(c.Scopes, " ")),
-	})
+//
+// Opts may include the PKCE verifier code if previously used in AuthCodeURL.
+// See https://www.oauth.com/oauth2-servers/pkce/ for more info.
+func (c *Config) Exchange(ctx context.Context, code string, opts ...AuthCodeOption) (*Token, error) {
+	v := url.Values{
+		"grant_type": {"authorization_code"},
+		"code":       {code},
+	}
+	if c.RedirectURL != "" {
+		v.Set("redirect_uri", c.RedirectURL)
+	}
+	for _, opt := range opts {
+		opt.setValue(v)
+	}
+	return retrieveToken(ctx, c, v)
 }
 
 // Client returns an HTTP client using the provided token.
 // NewClient creates an *http.Client from a Context and TokenSource.
 // The returned client is not valid beyond the lifetime of the context.
 //
+// Note that if a custom *http.Client is provided via the Context it
+// is used only for token acquisition and is not used to configure the
+// *http.Client returned from NewClient.
+//
 // As a special case, if src is nil, a non-OAuth2 client is returned
 // using the provided context. This exists to support related OAuth2
 // packages.
 func NewClient(ctx context.Context, src TokenSource) *http.Client {
 	if src == nil {
-		c, err := internal.ContextClient(ctx)
-		if err != nil {
-			return &http.Client{Transport: internal.ErrorTransport{Err: err}}
-		}
-		return c
+		return internal.ContextClient(ctx)
 	}
 	return &http.Client{
 		Transport: &Transport{
-			Base:   internal.ContextTransport(ctx),
+			Base:   internal.ContextClient(ctx).Transport,
 			Source: ReuseTokenSource(nil, src),
 		},
 	}

vendor/golang.org/x/oauth2/token.go

 package oauth2
 
 import (
+	"context"
+	"fmt"
 	"net/http"
 	"net/url"
 	"strconv"
 	"strings"
 	"time"
 
-	"golang.org/x/net/context"
 	"golang.org/x/oauth2/internal"
 )
 
 // expirations due to client-server time mismatches.
 const expiryDelta = 10 * time.Second
 
-// Token represents the crendentials used to authorize
+// Token represents the credentials used to authorize
 // the requests to access protected resources on the OAuth 2.0
 // provider's backend.
 //
 	if t.Expiry.IsZero() {
 		return false
 	}
-	return t.Expiry.Add(-expiryDelta).Before(time.Now())
+	return t.Expiry.Round(0).Add(-expiryDelta).Before(time.Now())
 }
 
 // Valid reports whether t is non-nil, has an AccessToken, and is not expired.
 func retrieveToken(ctx context.Context, c *Config, v url.Values) (*Token, error) {
 	tk, err := internal.RetrieveToken(ctx, c.ClientID, c.ClientSecret, c.Endpoint.TokenURL, v)
 	if err != nil {
+		if rErr, ok := err.(*internal.RetrieveError); ok {
+			return nil, (*RetrieveError)(rErr)
+		}
 		return nil, err
 	}
 	return tokenFromInternal(tk), nil
 }
+
+// RetrieveError is the error returned when the token endpoint returns a
+// non-2XX HTTP status code.
+type RetrieveError struct {
+	Response *http.Response
+	// Body is the body that was consumed by reading Response.Body.
+	// It may be truncated.
+	Body []byte
+}
+
+func (r *RetrieveError) Error() string {
+	return fmt.Sprintf("oauth2: cannot fetch token: %v\nResponse: %s", r.Response.Status, r.Body)
+}

vendor/golang.org/x/oauth2/transport.go

 }
 
 // RoundTrip authorizes and authenticates the request with an
-// access token. If no token exists or token is expired,
-// tries to refresh/fetch a new token.
+// access token from Transport's Source.
 func (t *Transport) RoundTrip(req *http.Request) (*http.Response, error) {
+	reqBodyClosed := false
+	if req.Body != nil {
+		defer func() {
+			if !reqBodyClosed {
+				req.Body.Close()
+			}
+		}()
+	}
+
 	if t.Source == nil {
 		return nil, errors.New("oauth2: Transport's Source is nil")
 	}
 	token.SetAuthHeader(req2)
 	t.setModReq(req, req2)
 	res, err := t.base().RoundTrip(req2)
+
+	// req.Body is assumed to have been closed by the base RoundTripper.
+	reqBodyClosed = true
+
 	if err != nil {
 		t.setModReq(req, nil)
 		return nil, err