HANA Spatial: How to get Points from Polygon?

[UweFetzer_se38]

In HANA you define a polygon by setting multiple points, for example

NEW ST_Polygon('Polygon ((-5 -5, 5 -5, 0 5, -5 -5), (-2 -2, -2 0, 2 0, 2 -2, -2 -2))')

Is it somehow possible to get the points of an already existing polygon? I can't find a reverse functionion in the documentation (and I don't want to misuse the ST_AsGeoJSON function for this).

[mkemeter · Accepted solution]

Hi Uwe,

you can achieve this by iterating over the exterior and interior rings of the polygon.

You can retrieve the exterior and interior rings of the polygon by using ST_ExteriorRing and ST_InteriorRingN. The number of points per ring can be queried with ST_NumPoints and the specific point can be retrieved with ST_PointN.

The documentation of the respective functions can be found here:
https://help.sap.com/viewer/cbbbfc20871e4559abfd45a78ad58c02/2.0.04/en-US/7a13f280787c10148dc893063d...

Another 'hack' would be to play with the WKT of the polygon - but this is somewhat similar to your GeoJSON example.

Regards,
Mathias

[UweFetzer_se38 · Accepted solution]

Hello Mathias,

ST_AsWKT() is an interesting idea. I Think I'll try this approach. But first I have to solve my other issue, because currently the result of the call is truncated (due to an HANA Client error?) in ABAP (see "HANA Client library: Large result string truncated in ABAP")