7.4 SDO_GEOR.calcCompressionRatio

Format

SDO_GEOR.calcCompressionRatio(
     georaster  IN SDO_GEORASTER 
     ) RETURN NUMBER;

Description

Returns the compression ratio of a specified GeoRaster object.

Parameters

georaster

GeoRaster object.

Usage Notes

The compression ratio is the sum of the sizes of all raster blocks (including pyramids) in the uncompressed GeoRaster object divided by the sum of these sizes in the compressed form of the object. If the input GeoRaster object is not compressed, the compression ratio is 1 (that is, 1:1).

For a given original GeoRaster object, the greater the compression ratio, the smaller is the compressed GeoRaster object. For example, a compression ratio of 20 (that is, 20:1), the data is compressed to 5 percent of its original size.

For more information about GeoRaster compression, see Compression and Decompression.

Examples

The following example returns the compression type and compression ratio for the GeoRaster object in the GEORASTER column of table GEORASTER_TABLE where the GEORID column value is 1.

SELECT sdo_geor.getCompressionType(georaster) compType,
    sdo_geor.calcCompressionRatio(georaster) compRatio
  FROM georaster_table WHERE georid=1;