diff --git a/analysis/language/ar/arabic_normalize.go b/analysis/language/ar/arabic_normalize.go
index 70705258..abf86018 100644
--- a/analysis/language/ar/arabic_normalize.go
+++ b/analysis/language/ar/arabic_normalize.go
@@ -46,15 +46,11 @@ func NewArabicNormalizeFilter() *ArabicNormalizeFilter {
 }
 
 func (s *ArabicNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		term := normalize(token.Term)
 		token.Term = term
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func normalize(input []byte) []byte {
diff --git a/analysis/language/cjk/cjk_bigram.go b/analysis/language/cjk/cjk_bigram.go
index 36cfc88d..0596447e 100644
--- a/analysis/language/cjk/cjk_bigram.go
+++ b/analysis/language/cjk/cjk_bigram.go
@@ -32,7 +32,7 @@ func (s *CJKBigramFilter) Filter(input analysis.TokenStream) analysis.TokenStrea
 	r := ring.New(2)
 	itemsInRing := 0
 
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	for _, token := range input {
 		if token.Type == analysis.Ideographic {
diff --git a/analysis/language/ckb/sorani_normalize.go b/analysis/language/ckb/sorani_normalize.go
index 9b414192..b264bb40 100644
--- a/analysis/language/ckb/sorani_normalize.go
+++ b/analysis/language/ckb/sorani_normalize.go
@@ -56,15 +56,11 @@ func NewSoraniNormalizeFilter() *SoraniNormalizeFilter {
 }
 
 func (s *SoraniNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		term := normalize(token.Term)
 		token.Term = term
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func normalize(input []byte) []byte {
diff --git a/analysis/language/ckb/sorani_stemmer_filter.go b/analysis/language/ckb/sorani_stemmer_filter.go
index aabce1c6..68367a55 100644
--- a/analysis/language/ckb/sorani_stemmer_filter.go
+++ b/analysis/language/ckb/sorani_stemmer_filter.go
@@ -27,18 +27,14 @@ func NewSoraniStemmerFilter() *SoraniStemmerFilter {
 }
 
 func (s *SoraniStemmerFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		// if not protected keyword, stem it
 		if !token.KeyWord {
 			stemmed := stem(token.Term)
 			token.Term = stemmed
 		}
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func stem(input []byte) []byte {
diff --git a/analysis/language/de/german_normalize.go b/analysis/language/de/german_normalize.go
index cc73ea65..47cc97b4 100644
--- a/analysis/language/de/german_normalize.go
+++ b/analysis/language/de/german_normalize.go
@@ -32,15 +32,11 @@ func NewGermanNormalizeFilter() *GermanNormalizeFilter {
 }
 
 func (s *GermanNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		term := normalize(token.Term)
 		token.Term = term
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func normalize(input []byte) []byte {
diff --git a/analysis/language/en/possessive_filter_en.go b/analysis/language/en/possessive_filter_en.go
index 128fbac9..84a62c2f 100644
--- a/analysis/language/en/possessive_filter_en.go
+++ b/analysis/language/en/possessive_filter_en.go
@@ -32,7 +32,6 @@ func NewPossessiveFilter() *PossessiveFilter {
 }
 
 func (s *PossessiveFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-
 	for _, token := range input {
 		runes := bytes.Runes(token.Term)
 		if len(runes) >= 2 {
@@ -46,7 +45,6 @@ func (s *PossessiveFilter) Filter(input analysis.TokenStream) analysis.TokenStre
 			}
 		}
 	}
-
 	return input
 }
 
diff --git a/analysis/language/fa/persian_normalize.go b/analysis/language/fa/persian_normalize.go
index 494b5597..ab67af3a 100644
--- a/analysis/language/fa/persian_normalize.go
+++ b/analysis/language/fa/persian_normalize.go
@@ -38,15 +38,11 @@ func NewPersianNormalizeFilter() *PersianNormalizeFilter {
 }
 
 func (s *PersianNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		term := normalize(token.Term)
 		token.Term = term
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func normalize(input []byte) []byte {
diff --git a/analysis/language/hi/hindi_normalize.go b/analysis/language/hi/hindi_normalize.go
index 1117c131..f9b607c6 100644
--- a/analysis/language/hi/hindi_normalize.go
+++ b/analysis/language/hi/hindi_normalize.go
@@ -26,15 +26,11 @@ func NewHindiNormalizeFilter() *HindiNormalizeFilter {
 }
 
 func (s *HindiNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		term := normalize(token.Term)
 		token.Term = term
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func normalize(input []byte) []byte {
diff --git a/analysis/language/hi/hindi_stemmer_filter.go b/analysis/language/hi/hindi_stemmer_filter.go
index 0ebd3bde..b4e6ddd6 100644
--- a/analysis/language/hi/hindi_stemmer_filter.go
+++ b/analysis/language/hi/hindi_stemmer_filter.go
@@ -27,18 +27,14 @@ func NewHindiStemmerFilter() *HindiStemmerFilter {
 }
 
 func (s *HindiStemmerFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		// if not protected keyword, stem it
 		if !token.KeyWord {
 			stemmed := stem(token.Term)
 			token.Term = stemmed
 		}
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func stem(input []byte) []byte {
diff --git a/analysis/language/ja/ja_morph_kagome.go b/analysis/language/ja/ja_morph_kagome.go
index 9989526e..415183d2 100644
--- a/analysis/language/ja/ja_morph_kagome.go
+++ b/analysis/language/ja/ja_morph_kagome.go
@@ -46,7 +46,7 @@ func (t *KagomeMorphTokenizer) Tokenize(input []byte) analysis.TokenStream {
 		prevstart int
 	)
 
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 	if len(input) < 1 {
 		return rv
 	}
diff --git a/analysis/token_filters/apostrophe_filter/apostrophe_filter.go b/analysis/token_filters/apostrophe_filter/apostrophe_filter.go
index 7f889ec5..853db823 100644
--- a/analysis/token_filters/apostrophe_filter/apostrophe_filter.go
+++ b/analysis/token_filters/apostrophe_filter/apostrophe_filter.go
@@ -29,18 +29,15 @@ func NewApostropheFilter() *ApostropheFilter {
 }
 
 func (s *ApostropheFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		firstApostrophe := bytes.IndexAny(token.Term, Apostrophes)
 		if firstApostrophe >= 0 {
 			// found an apostrophe
 			token.Term = token.Term[0:firstApostrophe]
 		}
-		rv = append(rv, token)
 	}
 
-	return rv
+	return input
 }
 
 func ApostropheFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
diff --git a/analysis/token_filters/cld2/cld2_filter.go b/analysis/token_filters/cld2/cld2_filter.go
index 2458564d..4349ef8a 100644
--- a/analysis/token_filters/cld2/cld2_filter.go
+++ b/analysis/token_filters/cld2/cld2_filter.go
@@ -33,7 +33,7 @@ func NewCld2Filter() *Cld2Filter {
 }
 
 func (f *Cld2Filter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	offset := 0
 	for _, token := range input {
diff --git a/analysis/token_filters/edge_ngram_filter/edge_ngram_filter.go b/analysis/token_filters/edge_ngram_filter/edge_ngram_filter.go
index 7372e4e8..f370aa9d 100644
--- a/analysis/token_filters/edge_ngram_filter/edge_ngram_filter.go
+++ b/analysis/token_filters/edge_ngram_filter/edge_ngram_filter.go
@@ -40,7 +40,7 @@ func NewEdgeNgramFilter(side Side, minLength, maxLength int) *EdgeNgramFilter {
 }
 
 func (s *EdgeNgramFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	for _, token := range input {
 		runeCount := utf8.RuneCount(token.Term)
diff --git a/analysis/token_filters/elision_filter/elision_filter.go b/analysis/token_filters/elision_filter/elision_filter.go
index e1baced8..61aa6137 100644
--- a/analysis/token_filters/elision_filter/elision_filter.go
+++ b/analysis/token_filters/elision_filter/elision_filter.go
@@ -35,8 +35,6 @@ func NewElisionFilter(articles analysis.TokenMap) *ElisionFilter {
 }
 
 func (s *ElisionFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		firstApostrophe := bytes.IndexAny(token.Term, Apostrophes)
 		if firstApostrophe >= 0 {
@@ -48,10 +46,8 @@ func (s *ElisionFilter) Filter(input analysis.TokenStream) analysis.TokenStream
 				token.Term = token.Term[firstApostrophe+1:]
 			}
 		}
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func ElisionFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
diff --git a/analysis/token_filters/keyword_marker_filter/keyword_marker_filter.go b/analysis/token_filters/keyword_marker_filter/keyword_marker_filter.go
index e950331f..062d2172 100644
--- a/analysis/token_filters/keyword_marker_filter/keyword_marker_filter.go
+++ b/analysis/token_filters/keyword_marker_filter/keyword_marker_filter.go
@@ -29,7 +29,6 @@ func NewKeyWordMarkerFilter(keyWords analysis.TokenMap) *KeyWordMarkerFilter {
 }
 
 func (f *KeyWordMarkerFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-
 	for _, token := range input {
 		word := string(token.Term)
 		_, isKeyWord := f.keyWords[word]
@@ -37,7 +36,6 @@ func (f *KeyWordMarkerFilter) Filter(input analysis.TokenStream) analysis.TokenS
 			token.KeyWord = true
 		}
 	}
-
 	return input
 }
 
diff --git a/analysis/token_filters/length_filter/length_filter.go b/analysis/token_filters/length_filter/length_filter.go
index f42c8c7d..118c583c 100644
--- a/analysis/token_filters/length_filter/length_filter.go
+++ b/analysis/token_filters/length_filter/length_filter.go
@@ -32,7 +32,7 @@ func NewLengthFilter(min, max int) *LengthFilter {
 }
 
 func (f *LengthFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	for _, token := range input {
 		wordLen := utf8.RuneCount(token.Term)
diff --git a/analysis/token_filters/lower_case_filter/lower_case_filter.go b/analysis/token_filters/lower_case_filter/lower_case_filter.go
index 7668bf4b..44884924 100644
--- a/analysis/token_filters/lower_case_filter/lower_case_filter.go
+++ b/analysis/token_filters/lower_case_filter/lower_case_filter.go
@@ -26,16 +26,12 @@ func NewLowerCaseFilter() *LowerCaseFilter {
 }
 
 func (f *LowerCaseFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		word := string(token.Term)
 		wordLowerCase := strings.ToLower(word)
 		token.Term = []byte(wordLowerCase)
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func LowerCaseFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
diff --git a/analysis/token_filters/ngram_filter/ngram_filter.go b/analysis/token_filters/ngram_filter/ngram_filter.go
index 903a81df..d1433e26 100644
--- a/analysis/token_filters/ngram_filter/ngram_filter.go
+++ b/analysis/token_filters/ngram_filter/ngram_filter.go
@@ -33,7 +33,7 @@ func NewNgramFilter(minLength, maxLength int) *NgramFilter {
 }
 
 func (s *NgramFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	for _, token := range input {
 		runeCount := utf8.RuneCount(token.Term)
diff --git a/analysis/token_filters/shingle/shingle.go b/analysis/token_filters/shingle/shingle.go
index 8b7f122f..90965092 100644
--- a/analysis/token_filters/shingle/shingle.go
+++ b/analysis/token_filters/shingle/shingle.go
@@ -32,7 +32,7 @@ func NewShingleFilter(min, max int, outputOriginal bool, sep, fill string) *Shin
 }
 
 func (s *ShingleFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	currentPosition := 0
 	for _, token := range input {
diff --git a/analysis/token_filters/shingle/shingle_test.go b/analysis/token_filters/shingle/shingle_test.go
index 42f114a4..d81ac57e 100644
--- a/analysis/token_filters/shingle/shingle_test.go
+++ b/analysis/token_filters/shingle/shingle_test.go
@@ -16,7 +16,7 @@ import (
 	"github.com/blevesearch/bleve/analysis"
 )
 
-func TestNgramFilter(t *testing.T) {
+func TestShingleFilter(t *testing.T) {
 
 	tests := []struct {
 		min            int
diff --git a/analysis/token_filters/stemmer_filter/stemmer_filter.go b/analysis/token_filters/stemmer_filter/stemmer_filter.go
index 6c476840..3640681b 100644
--- a/analysis/token_filters/stemmer_filter/stemmer_filter.go
+++ b/analysis/token_filters/stemmer_filter/stemmer_filter.go
@@ -22,18 +22,22 @@ import (
 const Name = "stem"
 
 type StemmerFilter struct {
-	lang    string
-	stemmer *snowball.Stemmer
+	lang        string
+	stemmerPool chan *snowball.Stemmer
 }
 
 func NewStemmerFilter(lang string) (*StemmerFilter, error) {
-	stemmer, err := snowball.New(lang)
-	if err != nil {
-		return nil, err
+	stemmerPool := make(chan *snowball.Stemmer, 4)
+	for i := 0; i < 4; i++ {
+		stemmer, err := snowball.New(lang)
+		if err != nil {
+			return nil, err
+		}
+		stemmerPool <- stemmer
 	}
 	return &StemmerFilter{
-		lang:    lang,
-		stemmer: stemmer,
+		lang:        lang,
+		stemmerPool: stemmerPool,
 	}, nil
 }
 
@@ -50,18 +54,16 @@ func (s *StemmerFilter) List() []string {
 }
 
 func (s *StemmerFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		// if not protected keyword, stem it
 		if !token.KeyWord {
-			stemmed := s.stemmer.Stem(string(token.Term))
+			stemmer := <-s.stemmerPool
+			stemmed := stemmer.Stem(string(token.Term))
+			s.stemmerPool <- stemmer
 			token.Term = []byte(stemmed)
 		}
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func StemmerFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
diff --git a/analysis/token_filters/stop_tokens_filter/stop_tokens_filter.go b/analysis/token_filters/stop_tokens_filter/stop_tokens_filter.go
index 8f429ff3..712302b8 100644
--- a/analysis/token_filters/stop_tokens_filter/stop_tokens_filter.go
+++ b/analysis/token_filters/stop_tokens_filter/stop_tokens_filter.go
@@ -29,7 +29,7 @@ func NewStopTokensFilter(stopTokens analysis.TokenMap) *StopTokensFilter {
 }
 
 func (f *StopTokensFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
+	rv := make(analysis.TokenStream, 0, len(input))
 
 	for _, token := range input {
 		tokenTerm := string(token.Term)
diff --git a/analysis/token_filters/truncate_token_filter/truncate_token_filter.go b/analysis/token_filters/truncate_token_filter/truncate_token_filter.go
index af648181..2b16cb08 100644
--- a/analysis/token_filters/truncate_token_filter/truncate_token_filter.go
+++ b/analysis/token_filters/truncate_token_filter/truncate_token_filter.go
@@ -31,8 +31,6 @@ func NewTruncateTokenFilter(length int) *TruncateTokenFilter {
 }
 
 func (s *TruncateTokenFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		wordLen := utf8.RuneCount(token.Term)
 		if wordLen > s.length {
@@ -45,10 +43,8 @@ func (s *TruncateTokenFilter) Filter(input analysis.TokenStream) analysis.TokenS
 			}
 			token.Term = newterm
 		}
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func TruncateTokenFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {
diff --git a/analysis/token_filters/unicode_normalize/unicode_normalize.go b/analysis/token_filters/unicode_normalize/unicode_normalize.go
index 798f3da3..12956bc0 100644
--- a/analysis/token_filters/unicode_normalize/unicode_normalize.go
+++ b/analysis/token_filters/unicode_normalize/unicode_normalize.go
@@ -54,14 +54,10 @@ func MustNewUnicodeNormalizeFilter(formName string) *UnicodeNormalizeFilter {
 }
 
 func (s *UnicodeNormalizeFilter) Filter(input analysis.TokenStream) analysis.TokenStream {
-	rv := make(analysis.TokenStream, 0)
-
 	for _, token := range input {
 		token.Term = s.form.Bytes(token.Term)
-		rv = append(rv, token)
 	}
-
-	return rv
+	return input
 }
 
 func UnicodeNormalizeFilterConstructor(config map[string]interface{}, cache *registry.Cache) (analysis.TokenFilter, error) {