diff --git a/index/scorch/segment/mem/build.go b/index/scorch/segment/mem/build.go
index d3344ce3..57d60dc8 100644
--- a/index/scorch/segment/mem/build.go
+++ b/index/scorch/segment/mem/build.go
@@ -95,6 +95,21 @@ func (s *Segment) initializeDict(results []*index.AnalysisResult) {
 	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]
diff --git a/index/scorch/segment/zap/build.go b/index/scorch/segment/zap/build.go
index 60d168e6..b3bbbab5 100644
--- a/index/scorch/segment/zap/build.go
+++ b/index/scorch/segment/zap/build.go
@@ -28,7 +28,7 @@ import (
 	"github.com/golang/snappy"
 )
 
-const version uint32 = 2
+const version uint32 = 3
 
 const fieldNotUninverted = math.MaxUint64
 
diff --git a/index/scorch/segment/zap/merge.go b/index/scorch/segment/zap/merge.go
index db03c998..b1eed28b 100644
--- a/index/scorch/segment/zap/merge.go
+++ b/index/scorch/segment/zap/merge.go
@@ -21,6 +21,7 @@ import (
 	"fmt"
 	"math"
 	"os"
+	"sort"
 
 	"github.com/RoaringBitmap/roaring"
 	"github.com/Smerity/govarint"
@@ -28,6 +29,8 @@ import (
 	"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,
@@ -101,13 +104,13 @@ func MergeToWriter(segments []*SegmentBase, drops []*roaring.Bitmap,
 
 	var dictLocs []uint64
 
-	fieldsInv := mergeFields(segments)
+	fieldsSame, fieldsInv := mergeFields(segments)
 	fieldsMap := mapFields(fieldsInv)
 
 	numDocs = computeNewDocCount(segments, drops)
 	if numDocs > 0 {
 		storedIndexOffset, newDocNums, err = mergeStoredAndRemap(segments, drops,
-			fieldsMap, fieldsInv, numDocs, cr)
+			fieldsMap, fieldsInv, fieldsSame, numDocs, cr)
 		if err != nil {
 			return nil, 0, 0, 0, 0, err
 		}
@@ -411,10 +414,8 @@ func persistMergedRest(segments []*SegmentBase, drops []*roaring.Bitmap,
 	return rv, fieldDvLocsOffset, nil
 }
 
-const docDropped = math.MaxUint64
-
 func mergeStoredAndRemap(segments []*SegmentBase, drops []*roaring.Bitmap,
-	fieldsMap map[string]uint16, fieldsInv []string, newSegDocCount uint64,
+	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.
 
@@ -436,6 +437,24 @@ func mergeStoredAndRemap(segments []*SegmentBase, drops []*roaring.Bitmap,
 	for segI, segment := range segments {
 		segNewDocNums := make([]uint64, segment.numDocs)
 
+		// 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 && (drops[segI] == nil || drops[segI].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?
@@ -527,13 +546,61 @@ func mergeStoredAndRemap(segments []*SegmentBase, drops []*roaring.Bitmap,
 	return storedIndexOffset, rv, nil
 }
 
-// mergeFields builds a unified list of fields used across all the input segments
-func mergeFields(segments []*SegmentBase) []string {
+// 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()
+	}
+
 	fieldsMap := map[string]struct{}{}
 	for _, segment := range segments {
 		fields := segment.Fields()
-		for _, field := range fields {
+		for fieldi, field := range fields {
 			fieldsMap[field] = struct{}{}
+			if len(segment0Fields) != len(fields) || segment0Fields[fieldi] != field {
+				fieldsSame = false
+			}
 		}
 	}
 
@@ -545,5 +612,8 @@ func mergeFields(segments []*SegmentBase) []string {
 			rv = append(rv, k)
 		}
 	}
-	return rv
+
+	sort.Strings(rv[1:]) // leave _id as first
+
+	return fieldsSame, rv
 }
diff --git a/index/scorch/segment/zap/merge_test.go b/index/scorch/segment/zap/merge_test.go
index 323fffed..bb09f831 100644
--- a/index/scorch/segment/zap/merge_test.go
+++ b/index/scorch/segment/zap/merge_test.go
@@ -398,6 +398,40 @@ func compareSegments(a, b *Segment) string {
 								fieldName, next.Term, aloc, bloc))
 						}
 					}
+
+					if fieldName == "_id" {
+						docId := next.Term
+						docNumA := apitrn.Number()
+						docNumB := bpitrn.Number()
+						afields := map[string]interface{}{}
+						err = a.VisitDocument(apitrn.Number(),
+							func(field string, typ byte, value []byte, pos []uint64) bool {
+								afields[field+"-typ"] = typ
+								afields[field+"-value"] = value
+								afields[field+"-pos"] = pos
+								return true
+							})
+						if err != nil {
+							rv = append(rv, fmt.Sprintf("a.VisitDocument err: %v", err))
+						}
+						bfields := map[string]interface{}{}
+						err = b.VisitDocument(bpitrn.Number(),
+							func(field string, typ byte, value []byte, pos []uint64) bool {
+								bfields[field+"-typ"] = typ
+								bfields[field+"-value"] = value
+								bfields[field+"-pos"] = pos
+								return true
+							})
+						if err != nil {
+							rv = append(rv, fmt.Sprintf("b.VisitDocument err: %v", err))
+						}
+						if !reflect.DeepEqual(afields, bfields) {
+							rv = append(rv, fmt.Sprintf("afields != bfields,"+
+								" id: %s, docNumA: %d, docNumB: %d,"+
+								" afields: %#v, bfields: %#v",
+								docId, docNumA, docNumB, afields, bfields))
+						}
+					}
 				}
 			}
 		}
diff --git a/index/scorch/segment/zap/read.go b/index/scorch/segment/zap/read.go
index 0c5b9e17..e47d4c6a 100644
--- a/index/scorch/segment/zap/read.go
+++ b/index/scorch/segment/zap/read.go
@@ -17,15 +17,27 @@ package zap
 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])
-	var n uint64
-	metaLen, read := binary.Uvarint(s.mem[docStoredStart : docStoredStart+binary.MaxVarintLen64])
-	n += uint64(read)
-	var dataLen uint64
-	dataLen, read = binary.Uvarint(s.mem[docStoredStart+n : docStoredStart+n+binary.MaxVarintLen64])
-	n += uint64(read)
-	meta := s.mem[docStoredStart+n : docStoredStart+n+metaLen]
-	data := s.mem[docStoredStart+n+metaLen : docStoredStart+n+metaLen+dataLen]
+	_, 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[storedOffset : storedOffset+binary.MaxVarintLen64])
+	n += uint64(read)
+
+	dataLen, read := binary.Uvarint(s.mem[storedOffset+n : storedOffset+n+binary.MaxVarintLen64])
+	n += uint64(read)
+
+	return indexOffset, storedOffset, n, metaLen, dataLen
+}
diff --git a/index/scorch/segment/zap/segment_test.go b/index/scorch/segment/zap/segment_test.go
index 704f9e72..9ce354ce 100644
--- a/index/scorch/segment/zap/segment_test.go
+++ b/index/scorch/segment/zap/segment_test.go
@@ -18,6 +18,7 @@ import (
 	"math"
 	"os"
 	"reflect"
+	"sort"
 	"testing"
 
 	"github.com/blevesearch/bleve/index"
@@ -574,6 +575,7 @@ func TestSegmentVisitableDocValueFieldsList(t *testing.T) {
 			t.Fatalf("segment VisitableDocValueFields err: %v", err)
 		}
 
+		sort.Strings(expectedFields[1:]) // keep _id as first field
 		if !reflect.DeepEqual(fields, expectedFields) {
 			t.Errorf("expected field terms: %#v, got: %#v", expectedFields, fields)
 		}