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Message Posted: Thu, 26 Jun 2003 @ 15:02:59 GMT


     
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Subj:   Re: Question about HASHROW
 
From:   Judge, James A

Joe,

The hashing algorithm is sort of (anyone is welcome to give a more precise description) rolling accumulator of the bytes in the "key" columns, into the 4 byte hash value. As such there is no guarantee that distinct "key" column values won't generate the same hash key. And since the maximum HASHROW value is x"FFFFFFFF" (4+ billion) any table with more than 4+ billion rows would have duplicates.

Your second query says that there are 21 "key" values with more than 1 occurrence, the 1st query - I'm not sure what it is telling me (that there are 3 million rows in the table but only 3M-51607 unique hash values?)



     
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