BUG #1629: subquery IN returns incorrect results

The following bug has been logged online:

Bug reference:      1629
Logged by:          mike g
Email address:      mike@thegodshalls.com
PostgreSQL version: 8.0
Operating system:   Windows 2000
Description:        subquery IN returns incorrect results
Details:

If I run this query:
SELECT distinct CAST(newprogram as varchar(60)) FROM
 (SELECT t.propnbr,
     CASE WHEN t.propname =  'A' THEN 'Am'
          WHEN t.propname =  'B' THEN 'AMm'
          WHEN t.propname =  'C' THEN 'I might vanish'
          WHEN t.propname =  'D' THEN 'Bem'
          WHEN t.propname =  'E' THEN 'Cm'
          WHEN t.propname =  'F' THEN 'Clm'
          WHEN t.propname =  'G' THEN 'Com'
          WHEN t.propname =  'H' THEN 'Dm'
          WHEN t.propname =  'I' THEN 'Er'
          WHEN t.propname =  'J' THEN 'Err'
          WHEN t.propname =  'K' THEN 'Em'
          WHEN t.propname =  'L' THEN 'Fm'
          WHEN t.propname =  'M' THEN 'Fm'
          WHEN t.propname =  'N' THEN 'Gm'
          WHEN t.propname =  'O' THEN 'Hm'
          WHEN t.propname =  'P' THEN 'Dm'
          WHEN t.propname =  'Q' THEN 'Lm'
          WHEN t.propname =  'R' THEN 'Nm'
          WHEN t.propname =  'S' THEN 'Om'
          WHEN t.propname =  'T' THEN 'Err'
          WHEN t.propname =  'U' THEN 'Rm'
          WHEN t.propname =  'V' THEN 'Tm'
          WHEN t.propname =  'W' THEN 'Tm'
          ELSE t.propname
      END as newprogram
   FROM example_data t
   INNER JOIN example_data2 b ON t.propco = b.propco
 WHERE
 upper(b.serviced) = 'STATE1' and
 t.propname  in ('A',
'B'
'C',  --switch me
'D',  -- and switch me
'E',
'F',
'G',
'H',
'I',
'J',
'K',
'L',
'M',
'N',
'O',
'P',
'Q',
'R',
'S',
'T',
'U',
'V',
'W',
'X')) as my_data

My results are:
newprogram
Am
Bem
Clm
Cm
Com
Dm
Em
Er
Err
Fm
Gm
Hm
Lm
Nm
Om
Rm
Tm


If I just change the order of the data for the IN subquery portion

SELECT distinct CAST(newprogram as varchar(60)) FROM
 (SELECT t.propnbr,
     CASE WHEN t.propname =  'A' THEN 'Am'
          WHEN t.propname =  'B' THEN 'AMm'
          WHEN t.propname =  'C' THEN 'I might vanish'
          WHEN t.propname =  'D' THEN 'Bem'
          WHEN t.propname =  'E' THEN 'Cm'
          WHEN t.propname =  'F' THEN 'Clm'
          WHEN t.propname =  'G' THEN 'Com'
          WHEN t.propname =  'H' THEN 'Dm'
          WHEN t.propname =  'I' THEN 'Er'
          WHEN t.propname =  'J' THEN 'Err'
          WHEN t.propname =  'K' THEN 'Em'
          WHEN t.propname =  'L' THEN 'Fm'
          WHEN t.propname =  'M' THEN 'Fm'
          WHEN t.propname =  'N' THEN 'Gm'
          WHEN t.propname =  'O' THEN 'Hm'
          WHEN t.propname =  'P' THEN 'Dm'
          WHEN t.propname =  'Q' THEN 'Lm'
          WHEN t.propname =  'R' THEN 'Nm'
          WHEN t.propname =  'S' THEN 'Om'
          WHEN t.propname =  'T' THEN 'Err'
          WHEN t.propname =  'U' THEN 'Rm'
          WHEN t.propname =  'V' THEN 'Tm'
          WHEN t.propname =  'W' THEN 'Tm'
          ELSE t.propname
      END as newprogram
   FROM example_data t
   INNER JOIN example_data2 b ON t.propco = b.propco
 WHERE
 upper(b.serviced) = 'STATE1' and
 t.propname  in ('A',
'B'
'D',  -- and switch me
'C',  --switch me
'E',
'F',
'G',
'H',
'I',
'J',
'K',
'L',
'M',
'N',
'O',
'P',
'Q',
'R',
'S',
'T',
'U',
'V',
'W',
'X')) as my_data

Gives this for a result
Am
Clm
Cm
Com
Dm
Em
Er
Err
Fm
Gm
Hm
I might vanish
Lm
Nm
Om
Rm
Tm

I will email a pg_dump of the two tables on request.
The results of either version are incorrect.

If you remove the IN subquery and replace each case with t.propname = 'A'
or... then correct results returned:

AMm
Am
Bem
Clm
Cm
Com
Dm
Em
Er
Err
Fm
Gm
Hm
I might vanish
Lm
Nm
Om
Rm
Tm