[search_helpers] add explain extra options (wip)

search_helpers.py

@@ -72,8 +72,9 @@
                             query=element,
                             fields=fields))
             should.append(dsl_query.Fuzzy(_all=element))
+    # TODO - careful with explain for performance reasons, maybe skip if nb terms < 3
     return search.query('bool',
                         must=must,
                         must_not=must_not,
                         should=should,
                         minimum_should_match="30%",
@@ -75,6 +76,6 @@
     return search.query('bool',
                         must=must,
                         must_not=must_not,
                         should=should,
                         minimum_should_match="30%",
-                        )
+                        ).extra(explain=True)