time difference between count(*) and count(id)

Mon, 06 Oct 2003 12:06:23 -0700 

Have seen postings before that count(*) is slower than counting on an
index.

However, I am seeing count(*) perform faster than count(id)!!

Explain for Count(*) is:

KIOSK  METRICS  METRICS_KIOSKID_EXECTIME_COPIES  INDEX SCAN                            
        1206  *
KIOSK                                                 RESULT IS COPIED   , COSTVALUE 
IS        1208

and takes 110 milliseconds.

Explain for count(id) is:

KIOSK  METRICS  METRICS_KIOSKID_EXECTIME_COPIES  INDEX SCAN                            
        1209  *
KIOSK                                                 RESULT IS COPIED   , COSTVALUE 
IS        1211

and takes approx 4.5 seconds!!!

Can someone please explain? (no pun intended!)

Thanks,

David




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