[postgis-users] Why should these boxes intersect?

[DrYSG]

Thank you Paul,

You certainly are the expert, and I have learned a great deal from you
posts, as well as the PostGIS book which sits on my desk with
your introduction.

So I will hope you will excuse the chutzpah, but to me it feels like
something is broken, and I don't think it is that hard to fix.

What do you think about this as an improvement to ST_intersects:

1. Implement a "pre-pass" check for polygons that span the anti-meridian
(180 longitude) (e.g. intersect with anti-meridian)
2. If there is intersection:
	a. Split the polygon into shards by the anti-meridian
	b. perform normal ST_Intersects of the shards against the other polygon (or
shards)
	c. Boolean AND the results
	d. use short-circuit logic if any intersection results in false
3. If no intersection proceed as normal

Notes: 

1. I say something feels broken because I sense it in your article & there
is no clue in the documentation about this.
2. The test #1 can be very low overhead (just checking if the all longitudes
are positive, all negative or mixed (and short circuiting if there are any
mixed which would indicate a span of the anti-meridian)
3. The case where there is a span of the anti-meridian will be rare (who has
that much data in the pacific?)
4. Yes, the code for handling the shards is not very elegant, but that
branch would not often be taken
5. Note that my geometry column of the database is GIST indexed and the
Boston rectangle is still picking up the one in the pacific, so the bounding
box optimization for indexed search seems to be not working so well.
6. ST_Within might have this same issue, but the same fix should work for it
(symmetry is wonderful!). 

The reason I do not want to go to GEOGRAPHY types is that my application is
using using a view-box (of a map) as the search box
against a 20 Million record database of map objects (images, features, etc.)
that are all represented as by rectangular bounding
boxes. The PostGIS notes talk a lot about he overheard of GEOGRAPHY types,
and it is overkill in this case. All I want to know
is what is in the view-box - and rough estimates will work for that.

- Yechezkal

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