Re: [HACKERS] Happy column dropping

On 2000-01-22, Tom Lane mentioned:

> > 2) how do I find out if the dropped column is referenced in a constraint,
> > trigger, rule (this is necessary for a correct RESTRICT/CASCADE
> > implementation)
>
> Actually it's worse than that: you need to be prepared to renumber the
> columns after the dropped one, too. Probably what you will need to do
> is read in and deparse all the relevant rules and triggers, then reparse
> them against the updated table schema. Ugly. And no, I have no idea
> how you even *find* all the relevant rules. (Jan?)

Perhaps their should be a pg_attribute.attisusedbytrigger::oid,
pg_attribute.attisconstrainedbyconstr::oid, etc. Eventually, I think, this
is unavoidable if you want DROP TABLE to do the right thing as well, and
scanning and decoding possibly hundreds of rules, triggers, and
constraints won't get you far.

--
Peter Eisentraut Sernanders väg 10:115
peter_e(at)gmx(dot)net 75262 Uppsala
http://yi.org/peter-e/ Sweden