[gdal-dev] Any trick to run SELECT gdal_get_pixel_value for lots of points?

[Rahkonen Jukka]

Hi,

I tried the new SQL function "gdal_get_pixel_value" from this PR https://github.com/OSGeo/gdal/pull/6877. It is made to query a single point at a time but with some SQL I managed to query a few points with one ogrinfo command. I think that the query works even the

ogrinfo -sql "SELECT gdal_get_pixel_value('P3412A.tif', 1, 'pixel', 100, 200) as p1 UNION SELECT gdal_get_pixel_value('P3412A.tif', 1, 'pixel', 100, 400) as p1 UNION SELECT gdal_get_pixel_value('P3412A.tif', 1, 'pixel', 300, 400) as p1" p3412A.gpkg --config OGR_SQLITE_ALLOW_EXTERNAL_ACCESS YES
INFO: Open of `p3412A.gpkg'
      using driver `GPKG' successful.

Layer name: SELECT
Geometry: None
Feature Count: 3
Layer SRS WKT:
(unknown)
p1: Real (0.0)
OGRFeature(SELECT):0
  p1 (Real) = 11.1850004196167

OGRFeature(SELECT):1
  p1 (Real) = 11.7200002670288

OGRFeature(SELECT):2
  p1 (Real) = 13.5690002441406

However, the SQL statement with UNIONs gets too long if user wants to query hundreds or points. Is there any simple trick, SQL based or other, to make such a query?
The ultimate use case would be to find an alternative for the GRASS function v.drape https://grass.osgeo.org/grass82/manuals/v.drape.html.

-Jukka Rahkonen-
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