Home Page for the TeradataForum
 

Archives of the TeradataForum

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


     
  <Prev Next>   <<First <Prev Next> Last>>  


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?)



     
  <Prev Next>   <<First <Prev Next> Last>>  
 
 
 
 
 
 
 
 
  
  Top Home Privacy Feedback  
 
 
Copyright for the TeradataForum (TDATA-L), Manta BlueSky    
Copyright 2016 - All Rights Reserved    
Last Modified: 15 Jun 2023