Re: B-tree fan-out - Mailing list pgsql-general

From Martijn van Oosterhout
Subject Re: B-tree fan-out
Date
Msg-id 20070623110937.GB11248@svana.org
Whole thread Raw
In response to B-tree fan-out  (cluster <skrald@amossen.dk>)
Responses Re: B-tree fan-out  (cluster <skrald@amossen.dk>)
Re: B-tree fan-out  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
On Fri, Jun 22, 2007 at 09:32:30PM +0200, cluster wrote:
> What is the fan-out (number of child nodes) on each B-tree node in
> postgresql? Is it dependent of the size of the keys being indexed? If
> so: How?

In postgres, everything is done in pages, so how ever many keys fit in
a page. Bigs keys mean less. For integers you can fit an awful lot of
keys.


> In B-trees all non-leaf nodes have a bunch of pointers to its child
> nodes. What is the size of such a pointer?

I imagine it's a page number, probably just a 32-bit integer.

Have a nice day,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.

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