Isn't this what Grouped Index Tuples is? On Tue, Aug 14, 2007 at 05:21:16PM -0400, Chris Browne wrote: > I recently had a chat with someone who was pretty intimate with Adabas > for a number of years who's in the process of figuring things out > about PostgreSQL. We poked at bits of the respective implementations, > seeing some similarities and differences. He pointed out one aspect > of index handling that could (in principle) be an interesting > optimization. > > Evidently, in Adabas, index leaf nodes were not simply tuples, but > lists where the index value would not be repeated. > > In PostgreSQL, if you have the index value 'abc', and there are 10 > tuples with that value, then you'll have a page full of tuples of the > following form: > > |abc|ptr[rec1]|abc|ptr[rec2]|abc|ptr[rec3]| ...and so forth... > > Now, the Adabas approach was rather different. It would only have the > index value once, and then have the list of tuple pointers: > > |abc|ptr[rec1],ptr[rec2],ptr[rec3],...[ptr[rec10]| > > This could allow a fair bit of compression, for cases where the index > value is not unique. > > There is a concommitant downside, that concurrent updates may fight > over a page, and, since there would be a higher density, there would > be more need to fight over pages. > > Does this seem pretty much like madness? Or is it a plausible "some > day ToDo"? > -- > "cbbrowne","@","acm.org" > http://linuxfinances.info/info/postgresql.html > "I don't do drugs anymore 'cause I find I get the same effect just by > standing up really fast." -- Jonathan Katz > > ---------------------------(end of broadcast)--------------------------- > TIP 4: Have you searched our list archives? > > http://archives.postgresql.org >
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-- Decibel!, aka Jim Nasby [EMAIL PROTECTED] EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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