From a941a0f31863ca99efcc443a4fe7cf5ca300620a Mon Sep 17 00:00:00 2001
From: Steve Yen <steve.yen@gmail.com>
Date: Tue, 25 Oct 2016 15:12:46 -0700
Subject: [PATCH 1/2] simplify DocumentFieldTerms append() usage

---
 index/upsidedown/index_reader.go | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/index/upsidedown/index_reader.go b/index/upsidedown/index_reader.go
index 7714dc0a..288adaf2 100644
--- a/index/upsidedown/index_reader.go
+++ b/index/upsidedown/index_reader.go
@@ -119,12 +119,7 @@ func (i *IndexReader) DocumentFieldTerms(id index.IndexInternalID, fields []stri
 	}
 	for _, entry := range back.termEntries {
 		if field, ok := fieldsMap[uint16(*entry.Field)]; ok {
-			terms, ok := rv[field]
-			if !ok {
-				terms = make([]string, 0)
-			}
-			terms = append(terms, *entry.Term)
-			rv[field] = terms
+			rv[field] = append(rv[field], *entry.Term)
 		}
 	}
 	return rv, nil

From 2a8237e8cc293295f26c022f12e0fadbafad7111 Mon Sep 17 00:00:00 2001
From: Steve Yen <steve.yen@gmail.com>
Date: Tue, 25 Oct 2016 15:20:49 -0700
Subject: [PATCH 2/2] optimize FacetsBuilder with cached fields & avoid some
 allocs

---
 index/index.go           |  2 +-
 index/store/kvstore.go   |  2 +-
 registry/store.go        |  4 ++--
 search/facets_builder.go | 12 +++++++-----
 4 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/index/index.go b/index/index.go
index ee1bd161..ffcf6dcc 100644
--- a/index/index.go
+++ b/index/index.go
@@ -87,7 +87,7 @@ type FieldTerms map[string][]string
 
 // FieldsNotYetCached returns a list of fields not yet cached out of a larger list of fields
 func (f FieldTerms) FieldsNotYetCached(fields []string) []string {
-	var rv []string
+	rv := make([]string, 0, len(fields))
 	for _, field := range fields {
 		if _, ok := f[field]; !ok {
 			rv = append(rv, field)
diff --git a/index/store/kvstore.go b/index/store/kvstore.go
index f3a0109b..34698c7b 100644
--- a/index/store/kvstore.go
+++ b/index/store/kvstore.go
@@ -16,7 +16,7 @@ package store
 
 import "encoding/json"
 
-// KVStore is an abstraction for working with KV stores.  Note that 
+// KVStore is an abstraction for working with KV stores.  Note that
 // in order to be used with the bleve.registry, it must also implement
 // a constructor function of the registry.KVStoreConstructor type.
 type KVStore interface {
diff --git a/registry/store.go b/registry/store.go
index ad118ed0..83187763 100644
--- a/registry/store.go
+++ b/registry/store.go
@@ -28,8 +28,8 @@ func RegisterKVStore(name string, constructor KVStoreConstructor) {
 	stores[name] = constructor
 }
 
-// KVStoreConstructor is used to build a KVStore of a specific type when 
-// specificied by the index configuration. In addition to meeting the 
+// KVStoreConstructor is used to build a KVStore of a specific type when
+// specificied by the index configuration. In addition to meeting the
 // store.KVStore interface, KVStores must also support this constructor.
 // Note that currently the values of config must
 // be able to be marshaled and unmarshaled using the encoding/json library (used
diff --git a/search/facets_builder.go b/search/facets_builder.go
index 89ad1bb8..702e2ec2 100644
--- a/search/facets_builder.go
+++ b/search/facets_builder.go
@@ -29,6 +29,7 @@ type FacetBuilder interface {
 type FacetsBuilder struct {
 	indexReader index.IndexReader
 	facets      map[string]FacetBuilder
+	fields      []string
 }
 
 func NewFacetsBuilder(indexReader index.IndexReader) *FacetsBuilder {
@@ -43,14 +44,15 @@ func (fb *FacetsBuilder) Add(name string, facetBuilder FacetBuilder) {
 }
 
 func (fb *FacetsBuilder) Update(docMatch *DocumentMatch) error {
-	var fields []string
-	for _, facetBuilder := range fb.facets {
-		fields = append(fields, facetBuilder.Field())
+	if fb.fields == nil {
+		for _, facetBuilder := range fb.facets {
+			fb.fields = append(fb.fields, facetBuilder.Field())
+		}
 	}
 
-	if len(fields) > 0 {
+	if len(fb.fields) > 0 {
 		// find out which fields haven't been loaded yet
-		fieldsToLoad := docMatch.CachedFieldTerms.FieldsNotYetCached(fields)
+		fieldsToLoad := docMatch.CachedFieldTerms.FieldsNotYetCached(fb.fields)
 		// look them up
 		fieldTerms, err := fb.indexReader.DocumentFieldTerms(docMatch.IndexInternalID, fieldsToLoad)
 		if err != nil {