Wildcard query on non existent field matches all documents

fixes elastic#2461

Author: kimchy

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

@@ -555,7 +555,18 @@ protected Query getWildcardQuery(String field, String termStr) throws ParseExcep
  if (termStr.equals("*")) {
  // we want to optimize for match all query for the "*:*", and "*" cases
  if ("*".equals(field) || Objects.equal(field, this.field)) {
- return newMatchAllDocsQuery();
+ String actualField = field;
+ if (actualField == null) {
+ actualField = this.field;
+ }
+ if (actualField == null) {
+ return newMatchAllDocsQuery();
+ }
+ if ("_all".equals(actualField)) {
+ return newMatchAllDocsQuery();
+ }
+ // effectively, we check if a field exists or not
+ return fieldQueryExtensions.get(ExistsFieldQueryExtension.NAME).query(parseContext, actualField);
  }
  }
  Collection<String> fields = extractMultiFields(field);