Multi indices search with nested fields
I think you need to use the indices query and to use a different query for each index. Something like this:
GET /questions,articles/_search{ "query": { "bool": { "must": [ { "bool": { "should": [ { "indices": { "indices": [ "questions" ], "query": { "nested": { "path": "answer", "query": { "term": { "text": "bla" } } } } } }, { "match_all": {} } ] } }, { "term": { "some_common_field": { "value": "whatever" } } } ] } }}