Re: cluster index on a table
От | Justin Pitts |
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Тема | Re: cluster index on a table |
Дата | |
Msg-id | EA2E96F9-5A9F-479D-845A-4AB7A7121669@gmail.com обсуждение исходный текст |
Ответ на | Re: cluster index on a table (Scott Carey <scott@richrelevance.com>) |
Список | pgsql-performance |
According to the books online http://msdn.microsoft.com/en-us/library/ms177443.aspx : "In a clustered index, the leaf nodes contain the data pages of the underlying table." Which agrees with your assertion. From a performance perspective, it DOES work very well. Which is why I keep hoping for it to show up in PostgreSQL. On Jul 16, 2009, at 2:21 PM, Scott Carey wrote: > I could be wrong, but I think MSSQL only keeps the data specified in > the > index in the index, and the remaining columns in the data. > That is, if there is a clustered index on a table on three columns > out of > five, those three columns in the index are stored in the index, > while the > other two are in a data portion. But it has been several years > since I > worked with that DB. > > They are certainly storing at least those columns in the index > itself. And > that feature does work very well from a performance perspective. > > IOT in Oracle is a huge win in some cases, but a bit more clunky for > others > than Clustered Indexes in MSSQL. Both are highly useful. > > On 7/16/09 10:52 AM, "Justin Pitts" <justinpitts@gmail.com> wrote: > >> ISTR that is the approach that MSSQL follows. >> >>> >>> Storing the full tuple in an index and not even having a data only >>> page >>> would also be an interesting approach to this (and perhaps simpler >>> than a >>> separate index file and data file if trying to keep the data in the >>> order of >>> the index). >> >> >
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