PostGIS ST_AsTIFF function raises memory exception

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We have a satellite image loaded into PostGIS. We've calculated a reflectance raster from that image and stored the pixels as 32BF pixels. There are 54 1000x1000 tiles in the reflectance raster.

I want to create a GeoTIFF of that reflectance raster. Individual tiles work fine. But using an ST_Union on the reflectance raster column raises an exception when executing the query below from Python:

SELECT ST_AsTIFF(ST_Union(refl_rast), 'GTiff') gtiffFROM sat_rast_calcInternalError: invalid memory alloc request size 1344128795I know I can export the tiles individually and merge them with gdal_merge.py afterwards. I'd prefer to export this GTiff in one step though. Should we:

  1. Use a different pixel type?
  2. Pass in another ST_AsGTIFF option?
  3. Increase a PostGRES memory parameter?
  4. Increase a Linux kernel parameter?
  5. Something else?
Any assistance would be much appreciated!



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