-- { echoOn }

EXPLAIN PLAN header = 1
SELECT count() FROM a JOIN b ON b.b1 = a.a1 JOIN c ON c.c1 = b.b1 JOIN d ON d.d1 = c.c1 GROUP BY a.a2
;
Expression ((Project names + Projection))
Header: count() UInt64
  Aggregating
  Header: __table1.a2 String
          count() UInt64
    Expression ((Before GROUP BY + DROP unused columns after JOIN))
    Header: __table1.a2 String
      Join (JOIN FillRightFirst)
      Header: __table1.a2 String
              __table3.c1 UInt64
        Expression ((JOIN actions + DROP unused columns after JOIN))
        Header: __table1.a2 String
                __table3.c1 UInt64
          Join (JOIN FillRightFirst)
          Header: __table1.a2 String
                  __table2.b1 UInt64
                  __table3.c1 UInt64
            Expression ((JOIN actions + DROP unused columns after JOIN))
            Header: __table1.a2 String
                    __table2.b1 UInt64
              Join (JOIN FillRightFirst)
              Header: __table1.a1 UInt64
                      __table1.a2 String
                      __table2.b1 UInt64
                Expression ((JOIN actions + Change column names to column identifiers))
                Header: __table1.a1 UInt64
                        __table1.a2 String
                  ReadFromMemoryStorage
                  Header: a1 UInt64
                          a2 String
                Expression ((JOIN actions + Change column names to column identifiers))
                Header: __table2.b1 UInt64
                  ReadFromMemoryStorage
                  Header: b1 UInt64
            Expression ((JOIN actions + Change column names to column identifiers))
            Header: __table3.c1 UInt64
              ReadFromMemoryStorage
              Header: c1 UInt64
        Expression ((JOIN actions + Change column names to column identifiers))
        Header: __table4.d1 UInt64
          ReadFromMemoryStorage
          Header: d1 UInt64
EXPLAIN PLAN header = 1
SELECT a.a2, d.d2 FROM a JOIN b USING (k) JOIN c USING (k) JOIN d USING (k)
;
Expression ((Project names + (Projection + DROP unused columns after JOIN)))
Header: a2 String
        d2 String
  Join (JOIN FillRightFirst)
  Header: __table1.a2 String
          __table1.k UInt64
          __table4.d2 String
    Expression (DROP unused columns after JOIN)
    Header: __table1.a2 String
            __table1.k UInt64
      Join (JOIN FillRightFirst)
      Header: __table1.a2 String
              __table1.k UInt64
        Expression (DROP unused columns after JOIN)
        Header: __table1.a2 String
                __table1.k UInt64
          Join (JOIN FillRightFirst)
          Header: __table1.a2 String
                  __table1.k UInt64
            Expression (Change column names to column identifiers)
            Header: __table1.a2 String
                    __table1.k UInt64
              ReadFromMemoryStorage
              Header: a2 String
                      k UInt64
            Expression (Change column names to column identifiers)
            Header: __table2.k UInt64
              ReadFromMemoryStorage
              Header: k UInt64
        Expression (Change column names to column identifiers)
        Header: __table3.k UInt64
          ReadFromMemoryStorage
          Header: k UInt64
    Expression (Change column names to column identifiers)
    Header: __table4.d2 String
            __table4.k UInt64
      ReadFromMemoryStorage
      Header: d2 String
              k UInt64
EXPLAIN PLAN header = 1
SELECT b.bx FROM a
JOIN (SELECT b1, b2 || 'x'  AS bx FROM b ) AS b ON b.b1 = a.a1
JOIN c ON c.c1 = b.b1
JOIN (SELECT number AS d1 from numbers(10)) AS d ON d.d1 = c.c1
WHERE c.c2 != '' ORDER BY a.a2
;
Expression (Project names)
Header: bx String
  Sorting (Sorting for ORDER BY)
  Header: __table1.a2 String
          __table2.bx String
    Expression ((Before ORDER BY + (Projection + )))
    Header: __table1.a2 String
            __table2.bx String
      Join (JOIN FillRightFirst)
      Header: __table1.a2 String
              __table2.bx String
              __table4.c2 String
              __table4.c1 UInt64
        Expression
        Header: __table1.a2 String
                __table2.bx String
                __table4.c2 String
                __table4.c1 UInt64
          Join (JOIN FillRightFirst)
          Header: __table1.a2 String
                  __table2.bx String
                  __table2.b1 UInt64
                  __table4.c2 String
                  __table4.c1 UInt64
            Expression ((JOIN actions + DROP unused columns after JOIN))
            Header: __table1.a2 String
                    __table2.bx String
                    __table2.b1 UInt64
              Join (JOIN FillRightFirst)
              Header: __table1.a1 UInt64
                      __table1.a2 String
                      __table2.bx String
                      __table2.b1 UInt64
                Expression ((JOIN actions + Change column names to column identifiers))
                Header: __table1.a1 UInt64
                        __table1.a2 String
                  ReadFromMemoryStorage
                  Header: a1 UInt64
                          a2 String
                Expression ((JOIN actions + (Change column names to column identifiers + (Project names + (Projection + Change column names to column identifiers)))))
                Header: __table2.b1 UInt64
                        __table2.bx String
                  ReadFromMemoryStorage
                  Header: b1 UInt64
                          b2 String
            Filter (( + (JOIN actions + Change column names to column identifiers)))
            Header: __table4.c1 UInt64
                    __table4.c2 String
              ReadFromMemoryStorage
              Header: c1 UInt64
                      c2 String
        Expression ((JOIN actions + (Change column names to column identifiers + (Project names + (Projection + Change column names to column identifiers)))))
        Header: __table5.d1 UInt64
          ReadFromSystemNumbers
          Header: number UInt64