> >> Each time the record is updated, a new version is created, thus
> >> lengthening the "correct" version search each time row is accessed,
> >> until, of course, the next vacuum comes along and corrects the
index
> >> to point to the latest version of the record.
> >>
> >> Is that a fair explanation?
> >
> > No, it's not.
> >
> > 1. The index points to all the versions, until they get vacuumed
out.
> it points to the last "current" version as updated by vacuum, or the
first version
> of the row.
no, the index has one entry for each version of the row.
This is why updating only non-indexed columns is relatively expensive
in pg.
Andreas