I tried to read compressed and uncompressed GeoRaster. The different in the performance confused me. I expected better performance for compressed raster, because Oracle needs to read in few times less data from hard drive (1:5 in my case). However, reading uncompressed data is approximately twice faster. I understand Oracle needs to use more CPU for uncompressing data. But I thought that saved time of reading data would be more than time for uncompressing a raster.
Did anybody compare the performance?
I do not know how ArcMap and FME do it. Oracle MapBuilder always calls sdo_geor.getRasterSusbet with a polygon geometry (could be in any coordinate system) to query the database. In general applications, because the query window is random, getRasterSusbet would find out the relevent raster blocks (in this case compressed) and then decompress, mosaic, clip and then return the result into the client for display. as you see there is an extra decompressing operation and that's why. I/O is very fast when you use securefiles for the georaster block storage.
You can try for yourself. QGIS is a free-open-source-software.
QGIS uses GDAL to access raster and vector data and there is a plugin called "Oracle Spatial GeoRaster", or just oracle-raster, to deal with GeoRaster. To access Geometries you don't need to activate the plugin, just select Oracle as your database "type" in the Add Vector Layer dialog box.
Displaying GeoRaster work pretty fast, as long as you have created pyramids. Yes, there is a little delay when the GeoRaster is compressed but that is because GDAL request the data to be uncompressed and QGIS has no clue about it.
Wouldn't be nice to have a viewer that used the JPEG as it is?
I don't see the option 'Oracle' in type. There are ODBC, ESRI, OGDIVectors, PostgreSQL and MySQL only.
I downloaded it from http://www.qgis.org/wiki/Download#Standalone_Installer_.28recommended_for_new_users.29 , Windows, Standalone Installer.
What is wrong?
Since you are using Windows, you should try get the OSGeo4W installer from here:
See how to use the installer here:
That doesn't include QGIS but you can find on "desktop applications" list.
I installed the appication. I added 2 layer - geometry and raster from Oracle. I can see geometry but I don't see the raster. Zoom to layer extent do nothing.
BTW, seems the application doesn't recognize the projection(Nad83/UTM zone 17N). I manually set the projection in Project property and in the property of the layer, but id doesn't help.
Oops, I got it. I have to use Select Oracle GeoRaster button instead of Add Vector Layer.
Edited by: Dmitry on Aug 5, 2010 2:42 PM
What indicates that it doesn't recognize NAD83/UTM17N ?
A blank screen could means that you need to change the symbology or select bands.
Can you runs this command on your GeoRaster and copy back the report to us?
gdalinfo geor:user/pwd@db,rdt,rid -mdd oracle
I don’t see an Oracle raster when I add it via “Layer”,”Add vector layer”.
I don’t think it is invisible; it rather was not loaded at all.
I can see the same raster when I use “Select Oracle GeoRaster” button.
So, it wasn't the projection issue.
BTW, when I try to open raster with pyramids the application just silenly close. I have no an issue with not pyramided rater.