Re: Hash index todo list item
От | Hannu Krosing |
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Тема | Re: Hash index todo list item |
Дата | |
Msg-id | 1189074288.7470.5.camel@hannu-laptop обсуждение исходный текст |
Ответ на | Re: Hash index todo list item (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: Hash index todo list item
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Список | pgsql-hackers |
Ühel kenal päeval, E, 2007-09-03 kell 19:55, kirjutas Tom Lane: > Gregory Stark <stark@enterprisedb.com> writes: > > "Kenneth Marshall" <ktm@rice.edu> writes: > >> - What about multi-column indexes? The current implementation > >> only supports 1 column. > > > That seems kind of weird. It seems obvious that you mix the three hashes > > together which reduces it to the solved problem. > > No, because part of the deal is that you can do lookups using only the > leading index columns. At least, all the existing multicolumn index > types can do that. One approahc is not to mix hashes, but to partition the hash, so that each column gets its N bits in the hash. If you do it smartly you can use any column for index lookups, not just the leading one. > regards, tom lane > > ---------------------------(end of broadcast)--------------------------- > TIP 9: In versions below 8.0, the planner will ignore your desire to > choose an index scan if your joining column's datatypes do not > match
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