Re: Allowing update of column only from trigger

PFC wrote [01/28/05 7:08 PM]:
>
>     First you should use a ltree type for the uri field :

Yes, it would be very good if I could use ltree rather than rolling my
own, but ltree doesn't meet my use requirements.

> - you write it foo.bar instead of /foo/bar

That is the problem: The point is to make look-up based on uri or
filesystem path very efficient.

> - there are operators on ltree types to express "is parent of", "is
> children of"
> - these operators are indexed

I have written similar pure-SQL functions for my parent/uri system,
though without the syntax shortcuts of the ltree operators.

> [...]
>     Now about your update problem, when you rename foo.bar into
> foo.crum.bar  you could, in a single update, replace all foo.bar by
> foo.crum.bar in all  your table with the ltree operators and special
> functions.

That's an approach I hadn't considered. Hmmm, I'd have to read the ltree
C sources to see how it does this....

>     And for your checks, you can add a CHECK on the url field to be sure
> it's  equal to the url of the parent + the name of the current row.
> It'll make  one more SELECT request, though.

Yes, I'd like to avoid extra selects as much as possible.

Thank you very much for your interaction -- very helpful.
--
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harrison@tbc.net