[postgis-devel] PATCH: New positional operators based on Y position of bounding boxes

[Mark Cave-Ayland]

Hi strk,

> -----Original Message-----
> From: strk at refractions.net [mailto:strk at refractions.net] 
> Sent: 11 January 2005 12:24
> To: Mark Cave-Ayland
> Cc: 'PostGIS Development Discussion'
> Subject: Re: [postgis-devel] PATCH: New positional operators 
> based on Y position of bounding boxes

(cut)
 
> Your naming is good, and having dopped box2d operators I 
> think Paul won't be against adding these *useful* ones.

Great. I've committed the changes to CVS.

> Then we should take a breath to plan release path.

OK. I did have a few things that I did notice from current CVS:

	- There is still mention of PG 7.1 in the .sql.in files, even though
LWGEOM
	is only supported for PG >= 7.2.


	- I did not notice any SRID checking in the LWGEOM_* functions in
lwgeom_gist.c.
	Hence the following works without throwing an error in CVS:

	mca1=# select astext(the_geom) from t1 where setSRID(the_geom, -1)
|&>
	 setSRID('POINT(0 0)'::geometry, -2);

	   astext
	------------
 	POINT(0 0)
 	POINT(0 1)
 	POINT(0 2)
	(3 rows)


	- It suddenly occurred to me that using the new operators, it may be
possible to
	devise a binary search algorithm to determine the extents of a
column. For example,
	using queries like:

		SELECT 1 FROM my_geom_column WHERE my_geom_column >>
'POINT(A B)' LIMIT 2

	where A and B are altered using a standard binary search, it should
be possible to
	quickly find the right-most geometry in the column when a GiST index
is present by
	looking at the number of records returned. If this is repeated for
the remaining 3
	sides then we have a "quick" way of accurately determining the
overall extent of a
	column.


Kind regards,

Mark.

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