It works very similarly to the way that ALTER TABLE ... ADD CHECK ..
works, with the tuple update added in.
Anyway, it's something like the below:
- Lock relation
- Pull out tuple
- Evaluate cooked default expression using EvalExpr
- heap_modifytuple (shove datum that EvalExpr returns into column)
- simple_heapupdate
- Goto step 2 (pull out next tuple)
On Thu, 2002-12-05 at 16:24, Christopher Kings-Lynne wrote:
> Hi guys,
>
> Messing about with ADD COLUMN...
>
> I'm not certain how to re-evaluate the default expression for each row? How
> do I do this? I have access to raw_default and cooked_default it seems.
>
> Thanks,
>
> Chris
>
>
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--
Rod Taylor <rbt@rbt.ca>
PGP Key: http://www.rbt.ca/rbtpub.asc