3 GeoRaster Operations

3.1 Creating the GeoRaster Table and Raster Data Table

Before you can work with GeoRaster objects, you must create a GeoRaster table and one or more raster data tables, if they do not already exist.

CREATE TABLE city_images (image_id NUMBER, image_description VARCHAR2(50), image SDO_GEORASTER);

CREATE TABLE city_images_rdt OF SDO_RASTER
  (PRIMARY KEY (rasterID, pyramidLevel, bandBlockNumber,
    rowBlockNumber, columnBlockNumber))
  TABLESPACE im_tbs_1
  LOB(rasterBlock) STORE AS lobseg
    (
     CHUNK 32768
     CACHE READS
     PCTVERSION 0
     STORAGE (PCTINCREASE 0)
    );

CREATE TABLE city_images_rdt OF SDO_RASTER
  (PRIMARY KEY (rasterID, pyramidLevel, bandBlockNumber,
    rowBlockNumber, columnBlockNumber))
  TABLESPACE im_tbs_2
  LOB(rasterBlock) STORE AS SECUREFILE lobseg
    (NOCACHE NOLOGGING);

3.2 Creating New GeoRaster Objects

Before you can store a GeoRaster image in a GeoRaster table, you must create the GeoRaster object and insert it into a GeoRaster table before you start working on it. To create a new GeoRaster object, you have the following options:

• Initialize an empty GeoRaster object, using the SDO_GEOR.init function.

• Create a blank GeoRaster object, using the SDO_GEOR.createBlank function.

You cannot perform any GeoRaster operations if the object has not been properly created (that is, if the object is an atomic null). The SDO_GEOR.init and SDO_GEOR.createBlank functions initialize GeoRaster objects with their raster data table and raster ID values if these are not already specified, and the GeoRaster DML trigger ensures that the raster data table name and raster ID value pair is unique for the current user.

If the new GeoRaster object will hold raster cell data (resulting from another GeoRaster procedure, such as SDO_GEOR.importFrom, SDO_GEOR.subset, or SDO_GEOR.copy), and if the raster data table for this new GeoRaster object does not exist, you must first create the raster data table. For information about creating a raster data table, including examples, see Section 3.1.2.

To avoid potential GeoRaster data problems (some of which are described in Section 3.20), you must register an initialized GeoRaster object in the GeoRaster system views by inserting the GeoRaster object into a GeoRaster table, and do this before you perform any other operations on the GeoRaster object. Any GeoRaster operations that need to manipulate the raster data table raise an exception if the source or target GeoRaster object is not registered.

3.3 Loading Raster Data

To load and export imagery or raster data, always consider third-party ETL tools (see the note in Section 1.13)

If you use features in GeoRaster to load raster data, you have the following options:

• Call the SDO_GEOR.importFrom procedure to load images into GeoRaster objects.

• Use the GeoRaster loader tool or viewer tool, which are described in Section 1.13.

With both options, you can do the following:

• Compress raster data and store the data in JPEG-compressed or DEFLATE-compressed GeoRaster objects.

• Load an ESRI world file or a Digital Globe RPC text file (.rpb) into an existing GeoRaster object, and georeference the raster data without reloading it. You can also specify an SRID with the world file and generate the spatial extent of the data.

• Load a GeoTIFF format file with georeferencing, with or without raster data.

After loading raster data into a GeoRaster object, you must ensure that the object is valid by calling the SDO_GEOR.validateGeoRaster function, as explained in Section 3.4.

Because an ESRI world file or .rpb file does not contain coordinate system information, you can specify the SRID value of a coordinate reference system for the load operation. However, if you do not specify an SRID, the model SRID of the GeoRaster objects is set to 0 (zero) by the loader, which means that the GeoRaster object is invalid, and therefore you must use the SDO_GEOR.setModelSRID procedure to specify a valid model space for this object. If you do not yet know the coordinate system of the model space, you can specify the SRID value as 999999, which means that the coordinate reference system is unknown. (Specifically, SRID 999999 is associated with a coordinate reference system named unknown CRS.) Later, when you know the actual coordinate reference system of the model space, you can set the SRID value accordingly.

For more information about the unknown CRS (SRID 999999) coordinate reference system, see Oracle Spatial Developer's Guide.

gdal_translate -of GTiff -co "TFW=YES" -co "INTERLEAVE=PIXEL" -co "TILED=YES" D:\my_image.tif D:\my_new_image.tif
 
gdal_translate -of GTiff -co "TILED=YES" -co "TFW=YES" D:\my_image.ecw D:\my_new_image.tif

java -Xmx1024m oracle.spatial.georaster.tools.GeoRasterLoader mymachine db11 6521 georaster georaster thin 32 T globe image "blocking=true, blocksize=(512,512,3)" "D:my_image.tif,2,RDT_15, D:\my_image.tfw,82213"

3.4 Validating GeoRaster Objects

Before you use a GeoRaster object or after you manually edit the raster data and metadata of a GeoRaster object, you should ensure that the object is valid. Validation for a GeoRaster object includes checking the registration of the GeoRaster object, checking the metadata and the raster cell data, and making sure that the metadata and data are consistent. For example, validation checks the raster type, dimension information, and the actual sizes of cell blocks, and it performs other checks.

If you used the GeoRaster loader tool described in Section 1.13, the GeoRaster objects were validated during the load operation.

GeoRaster provides the following validation subprograms:

• SDO_GEOR.validateGeoRaster validates the GeoRaster object, including cell data and metadata. It returns TRUE if the object is valid; otherwise, it returns one of the following: an Oracle error code indicating why the GeoRaster object is invalid, FALSE if validation fails for an unknown reason, or NULL if the GeoRaster object is null. You should always use this function after you create a GeoRaster object.

• SDO_GEOR.schemaValidate validates the metadata against the GeoRaster XML schema. You can use this function to locate errors if the SDO_GEOR.validateGeoRaster function returned the error code 13454. The SDO_GEOR.schemaValidate and SDO_GEOR.validateGeoRaster functions do not validate the spatial extent geometry.

• SDO_GEOR.validateBlockMBR validates the blockMBR geometry associated with each raster block stored in the raster data table. If there are any invalid blockMBR geometries, call the SDO_GEOR.generateBlockMBR procedure to regenerate them.

3.5 Georeferencing GeoRaster Objects

Georeferencing, as explained in Section 1.6, establishes the relationship between cell coordinates of GeoRaster data and real-world ground coordinates (or some local coordinates). If you need to georeference GeoRaster objects, the following approaches are available:

• If the original image is already georeferenced and if the georeferencing information is stored in an ESRI world file or .rpb file containing RPC coefficients you can use the SDO_GEOR.importFrom procedure to load an ESRI world file or .rpb file from a file or from a CLOB object, along with the image data itself (in either FILE or BLOB format). You can also use the GeoRaster client-side loader tool (described in Section 1.13) to load an ESRI world file or .rpb file from a file, along with the image file itself.

  Because an ESRI world file or .rpb file does not specify the model coordinate system, you can set the model space of the georeferenced GeoRaster object using an Oracle SRID in either of the following ways: specify the SRID along with the world file as a parameter to the SDO_GEOR.importFrom procedure or the GeoRaster client-side loader (described in Section 1.13); or, after loading the world file, call the SDO_GEOR.setModelSRID procedure. You can also call the SDO_GEOR.setModelSRID procedure to change the model space of a georeferenced GeoRaster object.

• If the original image is a georeferenced GeoTIFF image, you can use the SDO_GEOR.importFrom procedure to load the image with georeferencing, by specifying GEOTIFF as the input format. To load only the georeferencing information from a GeoTIFF image, without the raster image data, into an existing GeoRaster object, add the raster=false storage parameter. You can specify a backup SRID with the srid storage parameter, in case the GeoTIFF configuration values do not match any SRID recognized by Oracle Spatial.

  The GeoTIFF PixelIsArea raster space is equivalent to the GeoRaster upperleft-based cell coordinate system. An export to GeoTiff is always in PixelIsArea raster space, with a half-pixel adjustment of the affine transformation if the GeoRaster object is in center-based cell coordinate system. An import from GeoTIFF is always to the GeoRaster center-based cell coordinate system, with a half-pixel adjustment of the affine transformation if the GeoTIFF file is specified in PixelIsArea raster space.

  You can also use the GeoRaster client-side loader tool (described in Section 1.13) to load GeoTIFF images with georeferencing, using the storage parameter geotiff=true. If you omit this parameter or specify geotiff=false, the image is loaded as a simple TIFF image without georeferencing. The raster and srid storage parameters also apply to the client-side loader tool.

  To load or export GeoTIFF images with the GeoRaster client-side tools, add the following GeoTIFF libraries to your CLASSPATH definition:

  • xtiff-jai.jar (available from the SourceForge Extensible-TIFF-JAI group)

  • geotiff-jai.jar (available from the SourceForge GeoTIFF-JAI group)

  To load or export GeoTIFF images with the SDO_GEOR.importFrom or SDO_GEOR.exportTo procedure, load these libraries into the MDSYS schema by connecting to the database as the SYSTEM user, editing $ORACLE_HOME/md/admin/sdoldgtf.sql as needed to reflect the paths to the xtiff-jai.jar and geotiff-jai.jar files, and running the sdoldgtf.sql SQL*Plus script.

  If the database is downgraded to a release before Oracle Database 11g, these libraries should be uninstalled according to the script in $ORACLE_HOME/md/admin/sdormgtf.sql, editing it as needed to reflect the paths to the xtiff-jai.jar and geotiff-jai.jar files, and running the sdormgtf.sql script.

• You can use the SDO_GEOR.setSRS procedure to add, modify, and delete georeferencing information by directly accessing the GeoRaster SRS metadata. For example, you can create an SDO_GEOR_SRS object and assign the coefficients and related georeferencing information, and then call the SDO_GEOR.setSRS procedure to add or update the spatial reference information of any GeoRaster object. You can use the SDO_GEOR.setSRS procedure to set up the spatial reference information for all supported functional fitting georeferencing models. Examples of setting up the SRS information from an existing DLT model and from an existing RPC model are included in reference section for the SDO_GEOR.setSRS procedure.

  If you know that one GeoRaster object has the same SRS information as another GeoRaster object, you can call the SDO_GEOR.getSRS function to retrieve an SDO_GEOR_SRS object from this GeoRaster object, and then call the SDO_GEOR.setSRS procedure to georeference the first GeoRaster object.

• If the GeoRaster object can be georeferenced using an affine transformation, you can call the SDO_GEOR.georeference procedure to georeference a GeoRaster object directly. As described in the reference information for the SDO_GEOR.georeference, this procedure takes the coefficients A, B, C, D, E, F and other information, converts them into the coefficients a, b, c, d, e, f, and stores them in the spatial reference information of a GeoRaster object. If the original raster data is rectified and if the model coordinate of its origin (upper-left corner) is (x0, y0) and its spatial resolution or scale is s, then the following are true: A = s, B = 0, C = x0, D = 0, E = -s, F = y0.

Based on the SRS information of a georeferenced GeoRaster object, transforming GeoRaster coordinate information means finding the model (ground) coordinate associated with a specific cell (raster) coordinate, and the reverse. That is, you can do the following:

• Given a specific cell coordinate, you can find the associated model space coordinate using the SDO_GEOR.getModelCoordinate function. For example, if you identify a point in an image, you can find the longitude and latitude coordinates associated with that point.

• Given a model space coordinate, you can find the associated cell coordinate using the SDO_GEOR.getCellCoordinate function. For example, if you identify longitude and latitude coordinates, you can find the cell in an image associated with those coordinates.

3.6 Generating and Setting Spatial Extents

When a GeoRaster object is created, its spatial extent (spatialExtent attribute, described in Section 2.1.2) is not necessarily the enclosing geometry in its model space coordinate system. The spatial extent (footprint) geometry might initially be null, or it might reflect the cell space coordinate system or some other coordinate system. The ability to generate and set spatial extents is useful for building large GeoRaster databases of a global or large regional scope, in which the spatial extents are in one global geodetic coordinate system while the GeoRaster objects (imagery, DEMs, and so on) are in different projected coordinate systems. In such a case, you can create a spatial (R-tree) index on the spatial extents, which requires that all spatial extent geometries have the same SRID value.

To ensure that the spatial extent geometry of each GeoRaster object in a table is correct for its model space coordinate system (or for any other coordinate system that you may want to use), you must set the spatial extent. Moreover, to use a spatial index on the spatial extent geometries (described in Section 3.7), all indexed geometries must be based on the same coordinate system (that is, have the same SRID value).

You can set the spatial extent in either of the following ways: specify spatialExtent=TRUE as a storage parameter to the SDO_GEOR.importFrom procedure or the GeoRaster client-side loader (described in Section 1.13), or use the SQL UPDATE statement. If you use the SDO_GEOR.importFrom procedure or the loader, the SRID cannot be null or 0 (zero), and if there is an R-tree index on the GeoRaster spatial extent, the SRID of the spatial extent must match the SRID of the existing spatial index; otherwise, the spatial extent is set to a null value.

In addition, if you do not already have the spatial extent geometry, you can generate it using the SDO_GEOR.generateSpatialExtent function, and use that geometry to update the GeoRaster object. The following example updates the spatial extent geometry of a specified GeoRaster object in the CITY_IMAGES table (created in Example 3-1 in Section 3.1.1) to the generated spatial extent (reflecting the model coordinate system) of that object:

UPDATE city_images c
  SET c.image.spatialExtent = sdo_geor.generateSpatialExtent(image)
    WHERE c.image_id = 100;
COMMIT;

If you already know the spatial extent geometry for a GeoRaster object, or if you want the spatial extent geometry to be based on a coordinate system other than the one for the model space, construct the SDO_GEOMETRY object or select it from a table, and then update the GeoRaster object to set its spatial extent attribute to that geometry, as shown in the following example:

DECLARE
 geom sdo_geometry;
BEGIN
-- Set geom to an SDO_GEOMETRY object that covers the spatial extent
-- of the desired GeoRaster object. If necessary, perform coordinate
-- system transformation before setting geom.
-- geom := sdo_geometry(...);
  UPDATE city_images c
    SET c.image.spatialExtent = geom WHERE c.image_id = 100;
  COMMIT;
END;

3.7 Indexing GeoRaster Data

GeoRaster data can be indexed in various ways. The most important index you can create on a GeoRaster object is a spatial index on the spatial extent (footprint) geometry of the GeoRaster object (spatialExtent attribute, described in Section 2.1.2). For information about creating spatial indexes, see Oracle Spatial Developer's Guide.

You can also create one or more other indexes, such as:

• Function-based indexes on metadata objects using the Oracle XMLType or Oracle Text document indexing functionality

• Standard indexes on other user-defined columns of the GeoRaster table, such as cloud coverage, water coverage, or vegetation

You should also create a single B-tree index on the rasterId, pyramidLevel, bandBlockNumber, rowBlockNumber, and columnBlockNumber columns of each raster data table.

3.8 Changing Raster Storage

You can change some aspects of the way raster image data is stored: the raster blocking size, cell depth, interleaving type, and other aspects. To make such changes, use the SDO_GEOR.changeFormatCopy procedure, and specify the desired storage parameter values with the storageParam parameter. You can also specify storage parameters with several other functions and procedures that load and process a GeoRaster object to create another GeoRaster object.

For information about the storage parameters that you can specify, see Section 1.4.1.

3.9 Copying GeoRaster Objects

To copy a GeoRaster object, you must either copy it into an empty GeoRaster object or overwrite an existing valid GeoRaster object. (Empty GeoRaster objects are explained in Section 1.4.3.) To make an identical copy of the source GeoRaster object, use the SDO_GEOR.copy procedure; to make a copy that includes storage format changes, use the SDO_GEOR.changeFormatCopy procedure (see Section 3.8).

To copy a GeoRaster object using an empty GeoRaster object, follow these steps:

1. Initialize an empty GeoRaster object while inserting it into the destination table, returning the empty GeoRaster object.

2. Use the SDO_GEOR.copy or SDO_GEOR.changeFormatCopy procedure to copy the GeoRaster object into the returned empty GeoRaster object.

3. Use UPDATE statement to update the desired row in the destination table so that its GeoRaster column contains the copied GeoRaster object.

4. When you are ready to commit the transaction, use the COMMIT statement.

For an example of copying using an empty GeoRaster object, see the example for the SDO_GEOR.copy procedure inChapter 4.

To copy a GeoRaster object so that it overwrites (replaces) an existing GeoRaster object, follow these steps:

1. Select the existing GeoRaster object for update.

2. Use the SDO_GEOR.copy or SDO_GEOR.changeFormatCopy procedure to copy the selected GeoRaster object into either a valid existing GeoRaster object or an empty GeoRaster object.

3. Use UPDATE statement to update the desired row in the destination table so that its GeoRaster column contains the copied GeoRaster object.

4. When you are ready to commit the transaction, use the COMMIT statement.

For an example of copying to replace an existing GeoRaster object and to change its storage format, see the example for the SDO_GEOR.changeFormatCopy procedure inChapter 4.

3.10 Querying and Updating GeoRaster Metadata

You can query metadata for a GeoRaster object, and you can update many attributes of the metadata.

You can use many functions, most of whose names start with get, to query the metadata and ancillary information (for example, SDO_GEOR.getTotalLayerNumber and SDO_GEOR.hasPseudoColor).

You can use several subprograms, most of whose names start with set, to update metadata and ancillary data (for example, SDO_GEOR.setSRS and SDO_GEOR.setColorMap).

For many of the get functions, there is a corresponding procedure, whose name starts with set, to set, modify, or delete the value of a metadata attribute. For most set procedures, to delete the value of the metadata attribute that the procedure is designed to modify, specify a null value for the attribute. For example, to delete the bin table for a layer of a GeoRaster object, call the SDO_GEOR.setBinTable procedure and specify a null tableName parameter. However, in most cases you cannot specify a null value for other related attributes. For example, you cannot specify a null layerNumber parameter in a call to the SDO_GEOR.setBinTable procedure.

3.11 Querying and Updating GeoRaster Cell Data

To display part or all of a raster image, you can query the data for a cell (pixel), a range of cells, or the entire image associated with a GeoRaster object:

• SDO_GEOR.getCellValue returns the value of a single cell of the GeoRaster object.

• SDO_GEOR.getRasterSubset creates a single BLOB object containing all cells of a precise subset of the GeoRaster object (as specified by a window, layer or band numbers, and pyramid level). This BLOB object contains only raster cells and no related metadata.

• SDO_GEOR.getRasterData creates a single BLOB object containing all cells of the GeoRaster object at a specified pyramid level. This BLOB object contains only raster cells and no related metadata.

• SDO_GEOR.getRasterBlocks returns an object that includes all image data inside or touching a specified window. Specifically, it returns an object of the SDO_RASTERSET collection type that identifies all blocks of a specified pyramid level that are inside or touch a specified window.

You can also use the SDO_GEOR.exportTo procedure to export all or part of a raster image to a BLOB object (binary image format) or to a file of a specified file format type.

To update or change the value of raster cells in a specified window to a single value, you can use the SDO_GEOR.changeCellValue procedure. You can call the SDO_GEOR.updateRaster procedure to update a specified pyramid of a specified area, or the overlapping parts of one GeoRaster object, with a specified pyramid and specified bands or layers of another GeoRaster object. Both the SDO_GEOR.changeCellValue and the SDO_GEOR.updateRaster procedures support all pyramid levels, including the original raster data (that is, pyramid level 0).

If you want to change the raster data table name, use the SDO_GEOR_UTL.renameRDT procedure. In general, you should not directly update the attributes of a GeoRaster object, except for the spatialExtent attribute.

3.12 Processing GeoRaster Objects

You can perform a variety of processing operations on GeoRaster data, including changing the format, subsetting (cropping), scaling, generating pyramids and generating statistics and histograms. Some relevant subprograms are SDO_GEOR.changeFormatCopy, SDO_GEOR.subset, SDO_GEOR.mosaic, SDO_GEOR.generatePyramid, SDO_GEOR.deletePyramid, SDO_GEOR.scaleCopy, SDO_GEOR.mergeLayers, and SDO_GEOR.generateStatistics. See also the GeoRaster PL/SQL demo files, described in Section 1.14, for examples and explanatory comments.

3.13 Compressing and Decompressing GeoRaster Objects

You can reduce the storage space requirements for GeoRaster objects by compressing them using JPEG-B, JPEG-F, or DEFLATE compression. You can decompress any compressed GeoRaster object, although this is not required for any GeoRaster operations, because any GeoRaster operation that can be performed on an uncompressed (decompressed) GeoRaster object can be performed on a compressed GeoRaster object.

To compress or decompress a GeoRaster object, use the compression keyword in the storageParam parameter with the SDO_GEOR.changeFormatCopy procedure, or with several other procedures that load and process a GeoRaster object to create another GeoRaster object, including SDO_GEOR.importFrom, SDO_GEOR.mosaic, SDO_GEOR.scaleCopy, and SDO_GEOR.subset. (There are no separate procedures for compressing and decompressing a GeoRaster object.)

For more information about GeoRaster compression and decompression, see Section 1.10, including information about support for third-party compression solutions in Section 1.10.4.

3.14 Viewing GeoRaster Objects

To view GeoRaster objects, you have the following options:

• Call the SDO_GEOR.exportTo procedure to export GeoRaster objects to image files, and then display the images using image tools or a Web browser.

• Use the standalone GeoRaster viewer tool (one of the tools described in Section 1.13).

With the GeoRaster viewer tool, you can select a GeoRaster object of a database schema (user), query and display the whole or a subset of a GeoRaster object, zoom in and zoom out, scroll, and perform other basic operations. The pyramid level, cell coordinates, and model coordinates (if the object is georeferenced) are displayed for the point at the mouse pointer location. You can display individual cell values and choose different layers of a multiband or hyperspectral image for RGB full color display. The blocking boundaries can be overlapped on the top of the display. Depending on the data and your requests, the viewer can display the raster data in grayscale, pseudocolor, and 24-bit true color over an intranet or the Internet. Some of the basic GeoRaster metadata is also displayed.

The GeoRaster viewer tool provides a set of image processing operators for enhanced display of the GeoRaster objects, especially for those whose cell depth is greater than 8 or is a floating-point number. It can also display and apply bitmap masks on the GeoRaster objects if they have bitmap masks.

The GeoRaster viewer tool also includes menu commands to call the GeoRaster loader and exporter tools, thus enabling you to use a single tool as an interface to the capabilities of all the GeoRaster tools.

3.15 Exporting GeoRaster Objects

To load and export imagery or raster data, always consider third-party ETL tools (see the note in Section 1.13)

If you use features in GeoRaster to export GeoRaster objects to image files, you have the following options:

• Call the SDO_GEOR.exportTo procedure (which can export either to a file or to a BLOB object).

• Use the GeoRaster exporter tool or viewer tool, which are described in Section 1.13.

3.16 Updating GeoRaster Objects Before Committing

Before you commit a database transaction that inserts, updates, or deletes GeoRaster cell data or metadata, you should update the GeoRaster object. If you do not update the GeoRaster object after changing cell data, one or more of the following can result: an invalid GeoRaster object, dangling raster data, and inconsistent metadata. If you do not update the GeoRaster object after changing GeoRaster metadata, the metadata changes will not take effect.

If you decide to roll back the transaction instead of committing it, an UPDATE statement is not needed.

In Example 3-4, the UPDATE statement is required after the call to the SDO_GEOR.changeFormatCopy procedure and before the COMMIT statement.

DECLARE
    gr1 sdo_georaster;
    gr2 sdo_georaster;
BEGIN
    SELECT georaster INTO gr2 from georaster_table WHERE georid=11 FOR UPDATE;
    SELECT georaster INTO gr1 from georaster_table WHERE georid=1;
    sdo_geor.changeFormatCopy(gr1, 'blocksize=(2048,2048)', gr2);
    UPDATE georaster_table SET georaster=gr2 WHERE georid=11;
    COMMIT;
END;
/

3.17 Using Template-Related Subprograms to Develop GeoRaster Applications

The SDO_GEOR.createTemplate and SDO_GEOR.getRasterBlockLocator subprograms enable you to develop GeoRaster applications, such as ETL tools and image processing systems that work with GeoRaster objects, by reading and writing GeoRaster metadata and binary raster data without dealing directly with the Oracle XMLType, the GeoRaster XML schema, and Oracle BLOBs.

After you create a new GeoRaster object (explained in Section 3.2), you can use the SDO_GEOR.createTemplate function to populate the metadata of the GeoRaster object with basic information, such as raster type, dimension sizes, ultCoordinates, cell depth, interleaving type, blocking and block size, pyramid resampling method and reducing level, and compression method and quality. This function can optionally populate the raster data table with the correct number of rows and row data consisting of raster blocks containing empty BLOBs.

The XML metadata generated by the SDO_GEOR.createTemplate function conforms to the GeoRaster metadata schema. You can then use other GeoRaster subprogams to query or update the metadata (see Section 3.10).

You can use the SDO_GEOR.getRasterBlockLocator procedure to get the raster block locator by specifying the pyramid level and block number. If you have the raster block locator, you can then use the OCI or Java JDBC LOB interfaces to read and write the binary raster data. (The SDO_GEOR.getRasterBlockLocator procedure does not itself read or process LOB data.) To use this approach, you must understand the physical storage of the raster data (explained in Section 1.4), and you must compress and decompress the data as necessary before reading from or writing to the BLOB.

3.18 Using GeoRaster with Workspace Manager and Label Security

To use GeoRaster with Oracle Workspace Manager or Oracle Label Security, you must define an object view of SDO_RASTER type and use the object view as the raster storage. The object view must be defined on a single relational table (the base raster data table) that has all the necessary columns and the necessary primary key definition. The following example shows the general form of statements to create the table and the view:

CREATE TABLE <rdt_base_table> 
(  RASTERID NUMBER,
   PYRAMIDLEVEL NUMBER, 
   BANDBLOCKNUMBER NUMBER,
   ROWBLOCKNUMBER NUMBER,
   COLUMNBLOCKNUMBER NUMBER,
   BLOCKMBR MDSYS.SDO_GEOMETRY,
   RASTERBLOCK BLOB,
   PRIMARY KEY (RASTERID,PYRAMIDLEVEL,BANDBLOCKNUMBER,
                ROWBLOCKNUMBER,COLUMNBLOCKNUMBER)
) LOB (RASTERBLOCK) STORE AS (NOCACHE NOLOGGING);
 
CREATE VIEW <rdt_view> OF SDO_RASTER
 WITH OBJECT OID (RASTERID,PYRAMIDLEVEL,BANDBLOCKNUMBER,
                ROWBLOCKNUMBER,COLUMNBLOCKNUMBER)
 AS SELECT RASTERID,PYRAMIDLEVEL,BANDBLOCKNUMBER,ROWBLOCKNUMBER,COLUMNBLOCKNUMBER,
           BLOCKMBR,RASTRBLOCK 
      FROM <rdt_base_table>;

Use the name of the object view to create GeoRaster objects. For example (general format):

INSERT INTO georaster_table (georid, georaster)
  VALUES (0, SDO_GEOR.init(<rdt_view>));

The name of the object view is used in the RDT_TABLE_NAME column of the GeoRaster system data views (see Section 2.4). Grant the same privileges on the object view as you would for a raster object table. For example (general format)

GRANT SELECT,INSERT,UPDATE,DELETE on <rdt_view> TO SCOTT;

EXECUTE DBMS_WM.EnableVersioning (<rdt_base_table>, 'VIEW_WO_OVERWRITE');

declare
  geor sdo_georaster;
  cond varchar2(1000);
  lb   blob;
  r1   raw(1024);
  amt  number;
begin
  r1 := utl_raw.copies(utl_raw.cast_to_raw('0'),1024);
 
  select georaster into geor from georaster_table where georid=1;
  cond := 'rasterId=' || geor.rasterId || ' AND pyramidLevel=0 AND ' ||
          ' bandBlockNumber=0 AND rowBlockNumber=0 AND columnBlockNumber=0';
  dbms_wm.copyForUpdate(geor.rasterDataTable, cond);
  sdo_geor.getRasterBlockLocator(geor, 0, 0, 0, 0, lb, null, 'TRUE');
  amt := 1024;
  dbms_lob.write(lb, amt, 1, r1);
end;
/

3.19 Maintaining Efficient Tablespace Use by GeoRaster Objects

After delete or rollback operations, unused space allocated to a raster data table might not be promptly returned to the underlying tablespace. This could result in wasted tablespace area, and it can be a significant issue if the amount of raster data is large. If the raster data table is created using BasicFile LOBs in an automatic segment space management tablespace, you can explicitly shrink the rasterBlock LOB segment or the raster data table by altering the raster data table, as shown in Example 3-5 and Example 3-6.

ALTER TABLE city_images_rdt MODIFY LOB (rasterBlock) (SHRINK SPACE);

ALTER TABLE city_images_rdt ENABLE ROW MOVEMENT;
ALTER TABLE city_images_rdt SHRINK SPACE CASCADE;

If you are using SecureFiles, or if you are using BasicFiles allocated in a manual segment space management tablespace, you cannot reclaim unused space using the ALTER TABLE statements as shown in the preceding examples. Instead, you should create some working (for temporary use) raster data tables and try to put any intermittent results in these RDTs, and then drop these working RDTs after they are no longer needed.

3.20 Maintaining GeoRaster Objects and System Data in the Database

Although GeoRaster provides internal database mechanism to prevent the creation of invalid GeoRaster objects and system data, sometimes such GeoRaster objects and system data might exist in the database, especially after an upgrade from a previous release, or after some user errors in operations on GeoRaster system data. Examples of such invalid objects and system data include the following:

• An entry in the GeoRaster system data views (xxx_SDO_GEOR_SYSDATA, described in Section 2.4) refers to a nonexistent GeoRaster table or column.

• Two or more GeoRaster objects have the same pair of RDT name and raster ID values.

• Some GeoRaster objects, tables, columns, or RDTs not registered.

• An RDT name is not unique.

• A GeoRaster object is non-empty or nonblank, but an associated RDT does not exist.

After a database upgrade, you should call the SDO_GEOR_ADMIN.isUpgradeNeeded function to check for any invalid GeoRaster objects and invalid system data for the current version. If there are any errors or invalid data, call the SDO_GEOR_ADMIN.upgradeGeoRaster function to have the problems automatically corrected. If you connect as user MDSYS, the SDO_GEOR_ADMIN.upgradeGeoRaster function upgrades all GeoRaster objects in the database; otherwise, it upgrades only GeoRaster objects in the schema of the current user. (See the reference and usage information about SDO_GEOR_ADMIN.upgradeGeoRaster in Chapter 5.)

For regular maintenance due to possible user errors, several functions and procedures will be helpful in checking for and correcting invalid GeoRaster objects and system data entries:

• To check for errors, call SDO_GEOR_ADMIN.checkSysdataEntries and SDO_GEOR_ADMIN.listUnregisteredRDT.

• To check for dangling raster data, call SDO_GEOR_ADMIN.listRasterDanglingData.

• To correct all invalid system data entries, call SDO_GEOR_ADMIN.maintainSysdataEntries.

• To create correct DML triggers for all GeoRaster columns, call SDO_GEOR_ADMIN.registerGeoRasterColumns.

• To register all existing GeoRaster objects in the sysdata table, call SDO_GEOR_ADMIN.registerGeoRasterObjects.

See the reference and usage information about these procedures and functions in Chapter 5.

3.21 Transferring GeoRaster Data Between Databases

You can use either the Data Pump Export and Import utilities or the original Export and Import utilities to transfer GeoRaster data between databases. You must export and import rows from both the GeoRaster table and its related raster data table or tables. After the transfer, you do not need to insert the GeoRaster system data for the imported GeoRaster objects into the USER_SDO_GEOR_SYSDATA view (described in Section 2.4) in the target schema; however, you should use the SDO_GEOR.validateGeoRaster function to check the validity of imported GeoRaster objects before you perform any operations on these objects.

For information about the Data Pump Export and Import utilities and the original Export and Import utilities, see Oracle Database Utilities.

To transfer GeoRaster data between databases, follow these general steps:

1. Check for and resolve any conflicts, as explained in Section 3.21.1.

2. Perform the data transfer, as explained in Section 3.21.2.

expdp scott/tiger schemas=scott directory=dump_dir dumpfile=exp.dmp