I managed to extract raster values in PostGIS based on a table of point geometries by following Point sampling raster with PostGIS
SELECT id, ST_Value(rastertable.rast, 1, pointtable.geom) as RasterValue FROM rastertable, pointtable WHERE ST_Intersects(rastertable.rast, pointtable.geom) LIMIT 20
The above query takes roughly 20 seconds, which is one second per case. In the end I want to extract raster values for over 10 million points. With the current query that would take roughly 115 days; not really an option. How could I adjust the above query to increase the performance? Or do I maybe even need to change the method?
Edit: Using QGIS point sampling plugin also results in a 3 second per 10 point speed, reducing the waiting time to about 40 days. That still is not workable.