Re: Performance off "count(*)"

I think we are saying the same thing: the count can be determined by just the block header. No?

> As far as I know the "nrow" in block header stores number of all row
> structures in a block, including deleted rows (with delete flag set in row
> header) and continued row pieces (chained rows) so Oracle still has to go to
> individual row header to determine whether to count it or not...

>> A count(*) that uses TABLE ACCESS FULL access does not have
>> to read each block in its entirety, it just reads the header
>> to see how many rows are in the block.  I guess you could
>> call that "optimized".

-- 
Regards,
Greg Rahn
http://structureddata.org
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