| Subject | Re: [firebird-support] How to know when an index has become unbalanced? |
|---|---|
| Author | Helen Borrie |
| Post date | 2007-02-20T10:45:39Z |
At 07:11 PM 20/02/2007, you wrote:
"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$indices, those with the high numbers are the least selective.
./heLen
>considering your answer, is it correct to say that SET STATISTICSNo, SET STATISTICS hasn't anything to do with whether indexes are
>requests are now useless?
"balanced" or not (which is physical thing). It recalculates the
selectivity of the index, i.e. the distribution of values across the
index or, generically, its usefulness (high=good, low=bad). A unique
index has the highest selectivity since there is at most one
occurrence of its value[s]. If you are looking at the statistics
stored in rdb$indices, those with the high numbers are the least selective.
./heLen