Elasticsearch can-match phase

[qixian (wangjiajia)]

hello,who can help me with this question,thanks.
I konw that the old version of Elasticsearch before 7.16,during the can-match phase,the search’s coordinating node sent an individual request to each shard checked,is it contains the primary shard and replication shard ?

and the other question is whether the can-match phase only return the document id and then send second request get the complete document?

[qixian (wangjiajia)]

I have analyze the source code of Elasticsearch old version，I think The first question should contains all shards primary and replication；The second question is after the can-match phase which is prefilter the shards and next will execute the search accoding to the query type, which contains query_then_fetch and dfs_query_then_fetch