clickhouse-client --allow_experimental_analyzer=1 --query_kind secondary_query -q explain plan header=1 select toString(dummy) as dummy from system.one group by dummy
Expression ((Project names + Projection))
Header: dummy String
  Aggregating
  Header: toString(dummy_0) String
    Expression ((Before GROUP BY + Change column names to column identifiers))
    Header: toString(dummy_0) String
      ReadFromStorage (SystemOne)
      Header: dummy UInt8
clickhouse-local --allow_experimental_analyzer=1 --query_kind secondary_query -q explain plan header=1 select toString(dummy) as dummy from system.one group by dummy
Expression ((Project names + Projection))
Header: dummy String
  Aggregating
  Header: toString(dummy_0) String
    Expression ((Before GROUP BY + Change column names to column identifiers))
    Header: toString(dummy_0) String
      ReadFromStorage (SystemOne)
      Header: dummy UInt8
clickhouse-client --allow_experimental_analyzer=1 --query_kind initial_query -q explain plan header=1 select toString(dummy) as dummy from system.one group by dummy
Expression ((Project names + Projection))
Header: dummy String
  Aggregating
  Header: toString(dummy_0) String
    Expression ((Before GROUP BY + Change column names to column identifiers))
    Header: toString(dummy_0) String
      ReadFromStorage (SystemOne)
      Header: dummy UInt8
clickhouse-local --allow_experimental_analyzer=1 --query_kind initial_query -q explain plan header=1 select toString(dummy) as dummy from system.one group by dummy
Expression ((Project names + Projection))
Header: dummy String
  Aggregating
  Header: toString(dummy_0) String
    Expression ((Before GROUP BY + Change column names to column identifiers))
    Header: toString(dummy_0) String
      ReadFromStorage (SystemOne)
      Header: dummy UInt8