problem with volatile functions in subselects ?

["Sergey E. Koposov" <math(at)sai(dot)msu(dot)ru>]

Hello Hackers,

I see the very strange behaviour with the following set of queries:

wsdb=# select na,nb, na::double precision as da, nb::double precision  as db from ( select random()::numeric as na,random()::numeric as nb from generate_series(1,2)) as xx;
        na         |        nb         |        da         |        db 
-------------------+-------------------+-------------------+-------------------
 0.756045001445359 | 0.505602368389071 | 0.283893094995941 | 0.160685719065687
 0.792114335015469 | 0.416411793053342 | 0.342387438445532 | 0.531201674850286
(2 rows)

On my understanding that should produce the "na" column equal to "da" ?

When I do the same with the select from the table the result is similar:

wsdb=# select na,nb, na::double precision as da, nb::double precision  as db from ( select random()::numeric as na,random()::numeric as nb from pg_proc) as xx;
         na           |          nb           |          da          |          db 
-----------------------+-----------------------+----------------------+----------------------
     0.125243402610181 |     0.620239329347498 |     0.64666960465101 |    0.257827353318141
     0.934299875951512 |    0.0322264223509591 |     0.96565025298188 |   0.0439542480949099
........

But when I limit the select, I get the expected result.

wsdb=# select na,nb, na::double precision as da, nb::double precision  as db from ( select random()::numeric as na,random()::numeric as nb from pg_proc limit 2) as xx;
        na         |        nb         |        da         |        db 
-------------------+-------------------+-------------------+-------------------
 0.543030349324937 | 0.925069289712733 | 0.543030349324937 | 0.925069289712733
 0.934251406665077 | 0.292522935332974 | 0.934251406665077 | 0.292522935332974
(2 rows)

Is that a bug, or I'm missing something ?

PG version is 8.1.4 or 8.2dev.

Regards,
	Sergey

*******************************************************************
Sergey E. Koposov
Max Planck Institute for Astronomy/Sternberg Astronomical Institute
Tel: +49-6221-528-349
Web: http://lnfm1.sai.msu.ru/~math
E-mail: math(at)sai(dot)msu(dot)ru