Re: TODO: DROP COLUMN .. CASCADE

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Tom Lane wrote:
> >> Personally I'm not sold on the sensefulness of the TODO item to begin
> >> with.
> 
> > The current code just drops any index that inludes the dropped column,
> > even if the column is the second column in a multi-column index.  Does
> > that seem OK to you?
> 
> What's wrong with it?  Any unique constraint the index might have
> carried is no longer interesting, so there's no semantic reason for
> treating the index as an independent object.  And queries that might
> have referenced the column aren't going to work anymore, so the query
> mix changes and hence the index setup will really need rethinking anyhow.
> 
> Basically I think this proposal would introduce a weird, confusing
> dichotomy of behavior between single- and multi-column indexes.
> And as Rod pointed out, you'd logically have to do the same for CHECK
> constraints depending on whether they mention one or several columns.
> (And what of multicolumn foreign keys?)  I see much confusion ahead,
> and no payback. 

I do see the confusion argument, but I also see cases where folks are
losing the use of an index for single-column lookups.  Others?

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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