Correctly parse *:* query into matchAllDocsQuery

Fixes #2486

src/main/java/org/apache/lucene/queryparser/classic/MapperQueryParser.java

@@ -562,7 +562,7 @@ public class MapperQueryParser extends QueryParser {
                 if (actualField == null) {
                     return newMatchAllDocsQuery();
                 }
-                if ("_all".equals(actualField)) {
+                if ("*".equals(actualField) || "_all".equals(actualField)) {
                     return newMatchAllDocsQuery();
                 }
                 // effectively, we check if a field exists or not

src/test/java/org/elasticsearch/test/unit/index/query/SimpleIndexQueryParserTests.java

@@ -257,6 +257,17 @@ public class SimpleIndexQueryParserTests {
         assertThat((double) matchAllDocsQuery.getBoost(), closeTo(1.2, 0.01));
     }
 
+    @Test
+    public void testStarColonStar() throws Exception {
+        IndexQueryParserService queryParser = queryParser();
+        String query = copyToStringFromClasspath("/org/elasticsearch/test/unit/index/query/starColonStar.json");
+        Query parsedQuery = queryParser.parse(query).query();
+        assertThat(parsedQuery, instanceOf(ConstantScoreQuery.class));
+        ConstantScoreQuery constantScoreQuery = (ConstantScoreQuery) parsedQuery;
+        Filter internalFilter = constantScoreQuery.getFilter();
+        assertThat(internalFilter, instanceOf(MatchAllDocsFilter.class));
+    }
+
     @Test
     public void testDisMaxBuilder() throws Exception {
         IndexQueryParserService queryParser = queryParser();

src/test/java/org/elasticsearch/test/unit/index/query/starColonStar.json

@@ -0,0 +1,5 @@
+{
+    "query_string": {
+        "query": "*:*"
+    }
+}