--- In firebird-support@yahoogroups.com, "amoradell" <amoradell@...>
wrote:

>
> Hi,
>
> I have to load several thousands records in a database through text
> files of about 100000 records each.
>
> The records are put into several tables (about 20 with one exceding

10

> million records).
>
> For performance reasons, I must deactivate almost every index and

also

> triggers.
>
> I have only primary keys activated to avoid duplicates.
>
> I want to know if these indices on primary keys have their

statistics

> up to date or do I have to recompute them between each file to
> maintain good performance ?
>
> Thanks
>
> Alexandre
>

Selectivity is a measure of index duplicates. A selectivity of 5
means that for every value in the index, there are (on average) 5
records that contain this value. The lower the selectivity, the more
useful it is. A selectivity of 1 indicates a perfect one value to one
record match. Primary keys by definition require this. Therefore,
every primary key index and 'unique' constraint index will always
have a selectivity of 1, regardless of the number of records in the
table.

Adam