Hi Tom, > What needs more discussion is that it seems to me to make sense to extend the standard > opclasses to handle the four Y-direction operators comparable to the X-direction > operators that are already there, that is "above", "below", "overabove", and > "overbelow".
As part of PostGIS (http://postgis.refractions.net), I submitted a patch a while back to add additional Y-direction operators to the code which is a slightly modified version of rtree_gist (and yes, the PostGIS implementation will suffer from the same issues you've found with the existing R-tree implementations). The operators I went for were as follows: A &<| B - true if A's bounding box overlaps or is below B's bounding box A |&> B - true if B's bounding box overlaps or is above B's bounding box A <<| B - true if A's bounding box is strictly below B's bounding box A |>> B - true if A's bounding box is strictly above B's bounding box Since the rtree_gist implementation and operators were 2D, my thoughts were to use another op-class only if the indexing were upgraded to 3D. So with this in mind, I created the following new GiST strategies: #define RTOverBelowStrategyNumber 9 #define RTBelowStrategyNumber 10 #define RTAboveStrategyNumber 11 #define RTOverAboveStrategyNumber 12 This is basically what you are suggesting but with a | instead of a ^ in the operator name (my original choice was to try and use } to indicate the positive sense of the Y-axis but this was not accepted as a valid operator character which is why I changed to |). It would be harder for us to change these operators since they already exist, but then again it would be useful from a maintenance point of view to keep the strategy numbers and operators the same across both implementations. Of course strategy numbers are just used internally so these aren't such a big issue - it's more the choice of operators that would be useful to agree on. Kind regards, Mark. ------------------------ WebBased Ltd 17 Research Way Tamar Science Park Plymouth PL6 8BT T: +44 (0)1752 797131 F: +44 (0)1752 791023 W: http://www.webbased.co.uk ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
