Re: [HACKERS] Well, then you keep your darn columns

> > The only drawback of this scheme is that the space occupied by the
> > deleted column wouldn't go away immediately (in any given tuple,
> > it'd be reclaimed on the next UPDATE of the tuple).  On the other hand,
> > you could construe that as a feature --- you don't have to wait around
> > for a DROP COLUMN to finish.  Anyone who did want to reclaim space
> > immediately could do
> >     UPDATE table SET someothercolumn = someothercolumn;
> > followed by a VACUUM.  But I bet a lot of people would be just as
> > happy to let it happen in background.
> 
> Hey Bruce ... Look here ^^^^ :)
> 
> Oh, there is a second drawback to it though ...
> 
> DROP COLUMN name
> ADD COLUMN name <of a different type>
> 
> Then what? :(

Double-yikes.  There goes that idea, or does it?  Attributes are
numbered.  How does a missing attribute get handled for new rows?
My guess is that we have to keep this thing around forever.  Can you
imagine having all those user apps tha query pg_attribute supress that
column.  Sound like too much work to me.

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