Subject Re: [firebird-support] How to know when an index has become unbalanced?
Author Tetram Corp
thanks for explanation
to perfect my comprehension, what are the side effects of an
"unbalanced" index?

growing file size?
slowing index reading?


Helen Borrie a écrit :
> At 07:11 PM 20/02/2007, you wrote:
>> considering your answer, is it correct to say that SET STATISTICS
>> requests are now useless?
> No, SET STATISTICS hasn't anything to do with whether indexes are
> "balanced" or not (which is physical thing). It recalculates the
> selectivity of the index, i.e. the distribution of values across the
> index or, generically, its usefulness (high=good, low=bad). A unique
> index has the highest selectivity since there is at most one
> occurrence of its value[s]. If you are looking at the statistics
> stored in rdb$indices, those with the high numbers are the least selective.
> ./heLen