Re: [HACKERS] Slow count(*) again...

On PostgreSQL, the difference in no hints and hints for that one query 
with skewed data is that the query finishes a little faster.   On some 
others, which shall remain nameless, it is the difference between 
finishing in seconds or days, or maybe never.  Hints can be useful, but 
I can also see why they are not a top priority.  They are rarely needed, 
and only when working around a bug.  If you want them so badly, you have 
the source, write a contrib module  (can you do that on Oracle or 
MSSQL?)  If I have a choice between the developers spending time on 
implementing hints, and spending time on improving the optimiser, I'll 
take the optimiser.

Tom Kyte agrees:
http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:8912905298920
http://tkyte.blogspot.com/2006/08/words-of-wisdom.html



Oracle can be faster on count queries, but that is the only case I have 
seen.   Generally on most other queries, especially when it involves 
complex joins, or indexes on text fields, PostgreSQL is faster on the 
same hardware.