optimize query parsing to use single field parser when executing on single field

Author: kimchy

modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/FieldQueryParser.java

@@ -131,7 +131,7 @@ public class FieldQueryParser extends AbstractIndexComponent implements XContent
             return query;
         }
 
-        MapperQueryParser queryParser = parseContext.queryParser(qpSettings);
+        MapperQueryParser queryParser = parseContext.singleQueryParser(qpSettings);
 
         try {
             query = queryParser.parse(qpSettings.queryString());

modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/QueryParseContext.java

@@ -104,12 +104,12 @@ public IndexCache indexCache() {
         return indexQueryParser.indexCache;
     }
 
-    public MapperQueryParser queryParser(QueryParserSettings settings) {
+    public MapperQueryParser singleQueryParser(QueryParserSettings settings) {
         queryParser.reset(settings);
         return queryParser;
     }
 
-    public MultiFieldMapperQueryParser queryParser(MultiFieldQueryParserSettings settings) {
+    public MultiFieldMapperQueryParser multiQueryParser(MultiFieldQueryParserSettings settings) {
         multiFieldQueryParser.reset(settings);
         return multiFieldQueryParser;
     }

modules/elasticsearch/src/main/java/org/elasticsearch/index/query/xcontent/QueryStringQueryParser.java

@@ -177,13 +177,13 @@ public class QueryStringQueryParser extends AbstractIndexComponent implements XC
         if (qpSettings.fields() != null) {
             if (qpSettings.fields().size() == 1) {
                 qpSettings.defaultField(qpSettings.fields().get(0));
-                queryParser = parseContext.queryParser(qpSettings);
+                queryParser = parseContext.singleQueryParser(qpSettings);
             } else {
                 qpSettings.defaultField(null); // reset defaultField when using multi query parser
-                queryParser = parseContext.queryParser(qpSettings);
+                queryParser = parseContext.multiQueryParser(qpSettings);
             }
         } else {
-            queryParser = parseContext.queryParser(qpSettings);
+            queryParser = parseContext.singleQueryParser(qpSettings);
         }