topic Re: Function to generate unique number/key in load script in QlikView

Function to generate unique number/key in load script

Mon, 02 Dec 2013 15:16:26 GMT

I need to generate unique numbers/keys to replace a lengthy a concatenated key in the load script.

The unique number should be consistant and should persist reloads across different files. I'm not sure if autonumber() meets the requirement. I remember reading that it does not retain uniqueness. please advice.

Re: Function to generate unique number/key in load script

Clever_Anjos — Mon, 02 Dec 2013 15:28:38 GMT

Use Hash128/160/256. These functions has a very low chance of colision

Re: Function to generate unique number/key in load script

Anonymous — Mon, 02 Dec 2013 15:36:52 GMT

I agree with Clever, to do what you're asking, the best option is HashXXX(). Unless you're dealing with rows in the billions, I'd recommend Hash128. The only drawback that you'll find is that each unique instance requires 16 bytes (for Hash128, 160 is 20 bytes and 256 is 32 bytes per unique instance). This shouldn't be an issue if you are storing tables into QVD, but I would suggest wrapping an AutoNumber(hash_field, 'key_name') around your hashed fields when loading into an application meant for user consumption. It may slow down your reloads a little bit, but it will consume a lot less memory on load and should perform better.