Subject | RE: [firebird-support] Selectivity Question |
---|---|
Author | Helen Borrie |
Post date | 2003-11-05T07:56:20Z |
At 11:29 PM 4/11/2003 -0800, you wrote:
The value of SET STATISTICS and getstat is for troubleshooting performance
on tables you're actually using. The selectivity + the "geometry" stuff is
great for that.
Helen
>This is really great information. Are there any rules on when an indexWell, why would you want to have an index on a table with 2 records or 44?
>is more trouble to maintain than it is worth? Say if I have an index
>with a selectivity of 0.333 over 44 records. Also, it seems like one
>could easily be misled, for example, you might have a completely unique
>index but only currently have two records, thus resulting in a
>selectivity of 0.5.
The value of SET STATISTICS and getstat is for troubleshooting performance
on tables you're actually using. The selectivity + the "geometry" stuff is
great for that.
Helen