HASH function as a Uniqe number generator

eli_revach · October 2013

Hi
We like to use Vertica HASH() function, for generating numbers on top of scripts , did HASH function gurenty Uniqes ? so two diffrent string will never have the same same hash number ?.

Daniel_Leybovic · October 2013

>> did HASH function gurenty Uniqes ?
No.

Hash
Calculates a hash value over its arguments, producing a value in the range 0 <= x < 2^63.

So uniqueness not guaranteed, in sequence 0 <= Seq <= 2^63 + 1 must be exists at least one duplicate.
Pigeonhole principle: http://en.wikipedia.org/wiki/Pigeonhole_principle

eli_revach · October 2013

I agree ,i more ask about vertica imlemention

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HASH function as a Uniqe number generator

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