# Oracle Spatial

This driver supports reading and writing data in Oracle Spatial (8.1.7 or later) Object-Relational format. The Oracle Spatial driver is not normally built into OGR, but may be built in on platforms where the Oracle client libraries are available.

When opening a database, it's name should be specified in the form "OCI:userid/password@database_instance:table,table". The list of tables is optional. The database_instance portion may be omitted when accessing the default local database instance.

If the list of tables is not provided, then all tables appearing in ALL_SDO_GEOM_METADATA will be treated by OGR as layers with the table names as the layer names. Non-spatial tables or spatial tables not listed in the ALL_SDO_GEOM_METADATA table are not accessable unless explicitly listed in the datasource name. Even in databases where all desired layers are in the ALL_SDO_GEOM_METADATA table, it may be desirable to list only the tables to be used as this can substantially reduce initialization time in databases with many tables.

If the table has an integer column called OGR_FID it will be used as the feature id by OGR (and it will not appear as a regular attribute). When loading data into Oracle Spatial OGR will always create the OGR_FID field.

## SQL Issues

By default, the Oracle driver passes SQL statements directly to Oracle rather than evaluating them internally when using the ExecuteSQL() call on the OGRDataSource, or the -sql command option to ogr2ogr. Attribute query expressions are also passed through to Oracle.

As well two special commands are supported via the ExecuteSQL() interface. These are "DELLAYER:<table_name>" to delete a layer, and "VALLAYER:<table_name>" to apply the SDO_GEOM.VALIDATE_GEOMETRY() check to a layer. Internally these pseudo-commands are translated into more complex SQL commands for Oracle.

It's also possible to request the driver to handle SQL commands with OGR SQL engine, by passing "OGRSQL" string to the ExecuteSQL() method, as name of the SQL dialect.

## Caveats

- The type recognition logic is currently somewhat impoverished. No effort is made to preserve real width information for integer and real fields.
- Various types such as objects, and BLOBs in Oracle will be completely ignored by OGR.
- Currently the OGR transaction semantics are not properly mapped onto transaction semantics in Oracle.
- If an attribute called OGR_FID exists in the schema for tables being read, it will be used as the FID. Random (FID based) reads on tables without an identified (and indexed) FID field can be very slow. To force use of a particular field name the OCI_FID configuration variable (ie. environment variable) can be set to the target field name.
- Curved geometry types are converted to linestrings or linear rings in six degree segments when reading. The driver has no support for writing curved geometries.
- There is no support for point cloud (SDO_PC), TIN (SDO_TIN) and annotation text data types in Oracle Spatial.
- It might be necessary to define the environment variable NLS_LANG to "American_America.UTF8" to avoid issues with floating point numbers being truncated to integer on non-English environments.
- For developers: when running the driver under the memory error detection tool Valgrind, specifying the database_instance, typically to localhost, or with the TWO_TASK environment variable seems to be compulsory, otherwise "TNS:permission denied" errors will be reported)

## Creation Issues

The Oracle Spatial driver does not support creation of new datasets (database instances), but it does allow creation of new layers within an existing database.

Upon closing the OGRDataSource newly created layers will have a spatial index automatically built. At this point the USER_SDO_GEOM_METADATA table will also be updated with bounds for the table based on the features that have actually been written. One concequence of this is that once a layer has been loaded it is generally not possible to load additional features outside the original extents without manually modifying the DIMINFO information in USER_SDO_GEOM_METADATA and rebuilding the spatial index.

### Layer Creation Options

- OVERWRITE: This may be "YES" to force an existing layer of the desired name to be destroyed before creating the requested layer.

- TRUNCATE: This may be "YES" to force the existing table to be reused, but to first truncate all records in the table, preserving indexes or dependencies.

- LAUNDER: This may be "YES" to force new fields created on this layer to have their field names "laundered" into a form more compatible with Oracle. This converts to upper case and converts some special characters like "-" and "#" to "_". The default value is "NO".

- PRECISION: This may be "YES" to force new fields created on this layer to try and represent the width and precision information, if available using NUMBER(width,precision) or VARCHAR2(width) types. If "NO" then the types NUMBER, INTEGER and VARCHAR2 will be used instead. The default is "YES".

- DIM: This may be set to 2 or 3 to force the dimension of the created layer. If not set 3 is used by default.

- SPATIAL_INDEX: This may be set to FALSE to disable creation of a spatial index when a layer load is complete. By default an index is created if any of the layer features have valid geometries. The default is "YES". Note: option was called INDEX in releases before GDAL 2

- INDEX_PARAMETERS: This may be set to pass creation parameters when the spatial index is created. For instance setting INDEX_PARAMETERS to SDO_LEVEL=5 would cause a 5 level tile index to be used. By default no parameters are passed causing a default R-Tree spatial index to be created.

- ADD_LAYER_GTYPE=YES/NO: (starting with GDAL 2.0) This may be set to NO to disable the constraints on the geometry type in the spatial index, through the layer_gtype keyword in the PARAMETERS clause of the CREATE INDEX. Layers of type MultiPoint, MultiLineString or MultiPolygon will also accept single geometry type (Point, LineString, Polygon). Defaults to YES.

- DIMINFO_X: This may be set to xmin,xmax,xres values to control the X dimension info written into the USER_SDO_GEOM_METADATA table. By default extents are collected from the actual data written.

- DIMINFO_Y: This may be set to ymin,ymax,yres values to control the Y dimension info written into the USER_SDO_GEOM_METADATA table. By default extents are collected from the actual data written.

- DIMINFO_Z: This may be set to zmin,zmax,zres values to control the Z dimension info written into the USER_SDO_GEOM_METADATA table. By default fixed values of -100000,100000,0.002 are used for layers with a third dimension.

- SRID: By default this driver will attempt to find an existing row in the MDSYS.CS_SRS table with a well known text coordinate system exactly matching the one for this dataset. If one is not found, a new row will be added to this table. The SRID creation option allows the user to force use of an existing Oracle SRID item even it if does not exactly match the WKT the driver expects.

- MULTI_LOAD: If enabled new features will be created in groups of 100 per SQL INSERT command, instead of each feature being a separate INSERT command. Having this enabled is the fastest way to load data quickly. Multi-load mode is enabled by default, and may be forced off for existing layers or for new layers by setting to NO.

- LOADER_FILE: If this option is set, all feature information will be written to a file suitable for use with SQL*Loader instead of inserted directly in the database. The layer itself is still created in the database immediately. The SQL*Loader support is experimental, and generally MULTI_LOAD enabled mode should be used instead when trying for optimal load performance.

- GEOMETRY_NAME: By default OGR creates new tables with the geometry column named ORA_GEOMETRY. If you wish to use a different name, it can be supplied with the GEOMETRY_NAME layer creation option.

### Example

Simple translation of a shapefile into Oracle. The table 'ABC' will be created with the features from abc.shp and attributes from abc.dbf.

    % ogr2ogr -f OCI OCI:warmerda/password@gdal800.dreadfest.com abc.shp

This second example loads a political boundaries layer from VPF (via the OGDI driver), and renames the layer from the cryptic OGDI layer name to something more sensible. If an existing table of the desired name exists it is overwritten.

    % ogr2ogr  -f OCI OCI:warmerda/password \
            gltp:/vrf/usr4/mpp1/v0eur/vmaplv0/eurnasia \
            -lco OVERWRITE=yes -nln polbndl_bnd 'polbndl@bnd(*)_line'

This example shows using ogrinfo to evaluate an SQL query statement within Oracle. More sophisticated Oracle Spatial specific queries may also be used via the -sql commandline switch to ogrinfo.

    ogrinfo -ro OCI:warmerda/password -sql "SELECT pop_1994 from canada where province_name = 'Alberta'"

### Credits

I would like to thank SRC, LLC for it's financial support of the development of this driver.