On Wednesday 08 February 2006 06:18, Tom Lane wrote: > Dick Kniep <dick@xxxxxxxx> 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
