Re: Column storage positions

On Wed, 21 Feb 2007, Martijn van Oosterhout wrote:

> On Wed, Feb 21, 2007 at 12:06:30PM -0500, Phil Currier wrote:
> > Well, for two reasons:
> >
> > 1) If you have a table with one very-frequently-accessed varchar()
> > column and several not-frequently-accessed int columns, it might
> > actually make sense to put the varchar column first.  The system won't
> > always be able to make the most intelligent decision about table
> > layout.
>
> Umm, the point of the exercise is that if you know there are int
> columns, then you can skip over them, whereas you can never skip over a
> varchar column. So there isn't really any situation where it would be
> better to put the varchar first.

IIRC, in the first message in this thread, or another recent thread of
this type, someone tried a reordering example with alternating
smallints and varchar() and found that the leftmost varchar was
actually slower to access after reordering, so I'm not sure that we can
say there isn't a situation where it would affect things.