I have a perfomance issue :

I run PG (8.0.3) and SQLServer2000 on a Windows2000 Server (P4 1,5Ghz 512Mo)
I have a table (3200000 rows) and I run this single query :

select cod from mytable group by cod
I have an index on cod (char(4) - 88 different values)

PG = ~ 20 sec.
SQLServer = < 8 sec

the explain is :

HashAggregate  (cost=64410.09..64410.09 rows=55 width=8)
  ->  Seq Scan on mytable  (cost=0.00..56325.27 rows=3233927 width=8)

if I switch to "enable_hashagg = false" (just for a try...)
the planner will choose my index :

Group  (cost=0.00..76514.01 rows=55 width=8)
  ->  Index Scan using myindex on mytable  (cost=0.00..68429.20 rows=3233927

but performance will be comparable to previous test.

So with or without using Index I have the same result.

Thanks for help.
Stéphane COEZ

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TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not

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