Parent Join in elasticsearch is not searching as expected - elasticsearch

Question

We recently migrated from the elastic search version 5.5 to 7.7
The elastic search version 7.7 has removed the concept of the multiple types, so we used the JOIN data type for mapping the relationship between users and tweets like below
https://www.elastic.co/guide/en/elasticsearch/reference/current/parent-join.html
PUT twitter
{
"mappings": {
"properties": {
"my_id": {
"type": "keyword"
},
"my_join_field": {
"type": "join",
"relations": {
"users": "tweets"
}
}
}
}
}
so where the users is the parent and tweets are the children
My twitter index has 1 million entries in the combination of users and tweets,
It works as expected when I use hasParentQuery / hasChildQuery, I get the proper result.
But when I try to query only the parent in the twitter index (i.e) In this case, I want to search only on users in the twitter index, I query like below
// to filter only users
QueryBuilder query1 = QueryBuilders.matchQuery("my_join_field", "users");
// to get all the users whose name starts with joh...
QueryBuilder query2 = QueryBuilders.wildcardQuery("username", "*joh*").boost(1.0f);
BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery().must(resourceQuery).must(wildcard);
SearchResponse searResp = commondao.prepareSearch("twitter").setQuery(boolQueryBuilder).setFrom(from).setSize(size).execute().actionGet();
the twitter index has 1 million records with 50K entries of users and remaining as tweets.
This query is taking the same time (with / without passing the my_join_field as users) as searching the whole index.
What I am doing wrong? Any help is appreciated!