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","@",""
> "I don't do drugs anymore 'cause I  find I get the same effect just by
> standing up really fast." -- Jonathan Katz
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Decibel!, aka Jim Nasby                        [EMAIL PROTECTED]
EnterpriseDB      512.569.9461 (cell)

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