set ngram_tokenizer to english analyzer

lib/util/search.js

@@ -359,6 +359,7 @@ SearchClient.prototype.appendCriteriaForKeywordContains = function(query, keywor
         // TODO: By user's i18n setting, change boost or search target fields
         fields: [
           "path_ja^2",
+          "path_en^2",
           "body_ja",
           // "path_en",
           // "body_en",

resource/search/mappings.json

@@ -15,6 +15,14 @@
           "language":   "possessive_english"
         }
       },
+      "tokenizer": {
+        "ngram_tokenizer": {
+          "type": "ngram",
+          "min_gram": 2,
+          "max_gram": 3,
+          "token_chars": ["letter", "digit"]
+        }
+      },
       "analyzer": {
         "autocomplete": {
           "tokenizer":  "keyword",
@@ -24,7 +32,7 @@
           ]
         },
         "english": {
-          "tokenizer":  "standard",
+          "tokenizer":  "ngram_tokenizer",
           "filter": [
             "english_possessive_stemmer",
             "lowercase",