Re: Question about MIN/MAX optimization

On 25 abr, 12:52, Serge Rielau <srie...@[EMAIL PROTECTED]
> wrote:
> Try this then:
> SELECT *
> =A0 =A0FROM (SELECT abc FROM T WHERE ID =3D ?
> =A0 =A0 =A0 =A0 =A0 =A0ORDER BY id DESC, abc DESC FETCH FIRST ROW ONLY)
AS=
 Z,
> =A0 =A0 =A0 =A0 =A0(SELECT abc FROM T WHERE ID =3D ?
> =A0 =A0 =A0 =A0 =A0 =A0ORDER BY id ASC, abc ASC FETCH FIRST ROW ONLY) AS
Y=



I think it did not help. The plan is a much higher cost:

Access Plan:
-----------
        Total Cost:             64906.6
        Query Degree:           1

              Rows
             RETURN
             (   1)
              Cost
               I/O
               |
                1
             NLJOIN
             (   2)
             64906.6
             43706.8
          /-----+-----\
        1                1
     IXSCAN           IXSCAN
     (   3)           (   4)
      32453           32453.6
     21853.4          21853.4
       |                |
   1.48278e+06      1.48278e+06
 INDEX: RTM       INDEX: RTM
   IPSSTAT_WIN      IPSSTAT_WIN




Extended Diagnostic Information:
--------------------------------

No extended Diagnostic Information for this statment.


Plan Details:
-------------


        1) RETURN: (Return Result)
                ***ulative Total Cost:          64906.6
                ***ulative CPU Cost:            2.9567e+09
                ***ulative I/O Cost:            43706.8
                ***ulative Re-Total Cost:       1008.61
                ***ulative Re-CPU Cost:         2.66915e+09
                ***ulative Re-I/O Cost:         0
                ***ulative First Row Cost:      51.2763
                Estimated Bufferpool Buffers:   43707


Thanks for your inputs, Michel.