Re: [HACKERS] Re: order by and index path
От | Thomas G. Lockhart |
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Тема | Re: [HACKERS] Re: order by and index path |
Дата | |
Msg-id | 36260694.9139563E@alumni.caltech.edu обсуждение исходный текст |
Ответ на | Re: order by and index path (jwieck@debis.com (Jan Wieck)) |
Ответы |
Statistics on key distribution (was: Re: order by and index path)
Re: [HACKERS] Re: order by and index path |
Список | pgsql-hackers |
> We do not have this statistical information. So the whole > thing is at this time academic. I recall that Commercial Ingres made the assumption that one row (or 1% of rows? My memory of Ingres is fading :) would be returned from a qualified query if no statistics were available to suggest otherwise. It did collect statistics on data distribution to try to help make those optimizer choices. It may be reasonable to assume that if there is an index, then using it with any qualified query would be a win. Since the alternative is to decide to _not_ use an index, a decision for which we have no support with existing statistics. - Tom
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