Archives of the TeradataForum
Message Posted: Wed, 09 Apr 2014 @ 15:50:40 GMT
| Subj: | | Re: Problem with IDENTITY Column |
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| From: | | Geoffrey Rommel |
| | it does seem a sorry situation when two PE's working against the same Table can't even manage values into a Column without tripping over
each other .... because either that's what they were doing or there's a bug in the software (which is actually my suspicion). | |
This is not a bug. It's a necessary consequence of trying to generate distinct values across several parallel, shared-nothing processes. In
view of the database design, setting a maximum value of 5 on an identity column is not reasonable.
The quirks of this design have led many to recommend generating identity columns (surrogate keys, for example) in ETL outside the database.
Another problem is that identity columns are not guaranteed to retain their values when copying a table to another system. If that system has a
different number of AMPs, the generated values will be different. For my part, I hate identity columns and never use them.
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