Subject Re: [firebird-support] Re: High selectivity
Author Alexandre Benson Smith
At 22:14 26/09/2003 +0000, you wrote:
>sorry you mixed up again some things:
>bitmap indexes (yes oracle has them, but only the enterprise
>edition!!) are good for HIGH selectivity (e.g. table with 1 000 000
>records and you often select a few 100 000 records! low selectivity
>means that you search/select only a few records maybe 100 or 200. and
>for this LOW selectivity you normally use b-trees or b*-trees (if i
>am right firebird knows only b-trees).

Hi Alex,

I don't think so....

Index with High Selectivity means few records... low selectivity means a
lot of records...
Of course Helen have a better didactic and a better english to explain
that... see her post...

AFAIK FB has a B*-Tree variant...

Alexandre Benson Smith
THOR Software e Comercial Ltda.
Santo Andre - Sao Paulo - Brazil


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