[postgis-users] Getting ROOT MBR

[Mark Cave-Ayland]

On Sat, 2007-08-04 at 18:23 +0900, Kim Sang-hun wrote:
> Hi!!
> 
> i want to know root's mbr of table.
> 
> i made a function which calculating the range of the box with float type
> 
> and return it when i passed datum data to postgis,
> 
> and i want to know how to get datum information of root in postgres.
> 
> i know that blocknumber of root is GIST_ROOT_BLKNO, and i want to know how 
> can i
> 
> get datum data with using that or get it all in a time with using other 
> function.
> 
> thank you!
> 
> Sang-hun Kim


Hi there,

I've already had a go at producing code to do this: see
http://postgis.refractions.net/pipermail/postgis-devel/2005-January/000791.html for details but it is still incomplete; you should find it a useful example though.

The problem is this is that PostgreSQL doesn't store visibility
information in the index, so if you open the index then and read the MBR
then the bounding box could be bigger than reality since it offers a
containment for tuples that have been deleted - you still have to do
some sort of check on the heap.


Kind regards,

Mark.

-- 
ILande - Open Source Consultancy
http://www.ilande.co.uk