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javahashmd5apache-commonsuniqueidentifier

Good Hash function? (32-bit too small, 64-bit too large)

I need to generate a hash value used for uniqueness of many billions of records in Java. Trouble is, I only have 16 numeric digits to play with. In researching this, I have found algorithms for 32-bit hash, which return Java integers. But this is too small, as it only has a range of +/ 2 billion, and have will have more records that that. I cannot go to a 64-bit hash, as that will give me numeric values back that are too large (+/ 4 quintillion, or 19 digits). Trouble is, I am dealing with a legacy system that is forcing me into a static key length of 16 digits.

Suggestions? I know no hash function will guarantee uniqueness, but I need a good one that will fit into these restrictions.

Thanks

Solution

  • If your generated hash is too large you can just mod it with your keyspace max to make it fit.

    myhash = hash64bitvalue % 10^16