Subject Confusing selectivity for newly added index?
Author Kjell Rilbe

I have a table with around 170 million records. I just added a new
nullable column and an index on it. After having entered values into the
new column in only a few of the records, perhaps a few hundred or
thousand, I recomputed the selectivity for the new index.

I was astonished to see it set to 0.065 or something like that. Since
only a small number of records have a value, I would have expected a
much lower figure.

Or is selectivity computed only on non-null rows, and null rows entierly
left out of the calculation?


Kjell Rilbe
E-post: kjell@...
Telefon: 08-761 06 55
Mobil: 0733-44 24 64