Re: plans for bitmap indexes?
От | Zeugswetter Andreas DAZ SD |
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Тема | Re: plans for bitmap indexes? |
Дата | |
Msg-id | 46C15C39FEB2C44BA555E356FBCD6FA40184D1E0@m0114.s-mxs.net обсуждение исходный текст |
Ответ на | plans for bitmap indexes? (Yann Michel <yann-postgresql@spline.de>) |
Ответы |
Re: plans for bitmap indexes?
Re: plans for bitmap indexes? |
Список | pgsql-hackers |
> > The most nearly comparable thing is be the notion of "partial > > indexes," where, supposing you had 60 region codes (e.g. - 50 US > > states, 10 Canadian provinces), you might set up indices thus: > For example, imagine you have a table on a dating website with 18 columns > representing 18 different characteristics for matching. Imagine that you > index each of those columns seperately. If you do: > > SELECT * FROM people WHERE orientation = 'gay' AND gender = 'male' AND city = > 'San Francisco'; I think bitmap indexes do have valid use cases, but partitioned indexes are really a wonderful feature with a lot of use cases, maybe including this one. Workable examples for useful partitioned indexes, that help here are: create index people_male_ix on people (city) where gender = 'male'; create index people_gay_ix on people (city) where orientation = 'gay'; create index people_male_gay_ix on people (city) where gender = 'male' and orientation = 'gay'; Note, that the indexed column differs from the partitioning clause. Note also, that the last index will perform way better than a combo of bitmap indexes. Andreas
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