On Wednesday 08 February 2006 06:18, Tom Lane wrote:
> Dick Kniep <dick@kniep.nl> writes:
> > Does this also affect if you have many NULL values in the key? So testing
> > Not is NULL would also be affected?
>
> IS NOT NULL isn't an indexable operation, so your question doesn't really
> apply :-(
Does this mean that if you have a table that has many rows, and 95% of the
rows contain a NULL value for a field, that indexing will be useless, because
it will always do a tablescan?
Hope not!
Dick
