ganos.raster.md5sum_chunk_size is an integer GUC variable that controls how much data (in MB) is buffered per read operation when Ganos Raster computes an MD5 hash. The default value is 10. Valid values range from 1 to 256.
The value is interpreted as megabytes.
Examples
Set for the current session
SET ganos.raster.md5sum_chunk_size = 20;