ST_BandFileSize — Returns the file size of a band stored in file system. If no bandnum specified, 1 is assumed.
bigint ST_BandFileSize(raster rast, integer bandnum=1
Returns the file size of a band stored in file system. Throws an error if called with an in db band, or if outdb access is not enabled.
This function is typically used in conjunction with ST_BandPath() and ST_BandFileTimestamp() so a client can determine if the filename of a outdb raster as seen by it is the same as the one seen by the server.