How Open Source King.Oracle FDO provider uses Oracle Spatial
This document describe how King.Oracle provider will read
Oracle Spatial Tables and how to configure them for optimal use.
Quick Reference to Oracle Spatial
Oracle Spatial Geometry Type
Oracle Spatial supports object relational model for representing
geometry. Geometry is stored in native spatial data type
Oracle Geometry Metadata Views
To create an Spatial Index for an SDO_GEOMETRY column there has to
be a row in USER_SDO_GEOM_METADATA view.
Row in USER_SDO_GEOM_METADATA contains Table Name, Column Name of
geometry, information about lower and upper bound of every
dimension, tolerance of every dimension and SRID Coordinate
System (Spatial Reference System) identifier.
Oracle Spatial Index
Oracle Spatial lets you create Spatial Index
on geometry column. For Spatial Index R-tree indexing is used
(Oracle supports also quadtree indexing but it is discouraged).
Spatial Index has layer geometry type parameter which defines which
type of geometries are included in layer. It can be point, line,
polygon or combination of those.
An SRID (Spatial Reference
Identifier) is an integer value a key to MDSYS.CR_SYS table
describing coordinate systems. If no coordinate system is defined
SRID is NULL value.
How King.Oracle uses Oracle
King.Oracle provider will read
ALL_SDO_GEOM_METADATA View and find tables and columns with
SDO_GEOMETRY data type. For each pair Table-Column King.Oracle will
create an FDO Feature class. If you want a FDO Feature class to be
created based on Oracle View than you need to add a row in
USER_SDO_GEOM_METADATA for that View.
Configuration parameter for King.Oracle provider "OracleSchema"
determines if all raws from ALL_SDO_GEOM_METADATA will be used or
just rows with Owner equal to "OracleSchema".
Name of FDO Feature class is created based on Oracle Schema, Table
Name and Column Name of the geometry (Schema~TableName~ColumnName).
Spatial Index and Layer Geometry Type
creating Spatial index in Oracle you can set parameter layer_gtype
which defines type of geometry used in geometry column. Type can be
one of: POINT, MULTIPOINT, LINE, MULTILINE, POLYGON, MULTIPOLYGON,
COLLECTION or you can create index without specifying geometry type.
If you define layer type you can ensure that all geometries inserted
into table are of that type.
King.Oracle will use this type to define correct layer type for
MapGuide. So if this parameter is defined King.Oracle provider will
read it and setup correct layer type in MapGuide (
point, line, polygon).
You can use Fdo2Fdo tool to
find right layer type and create a spatial index in Oracle.
Layer Extent and SDO_GEOM_METADATA
MapGuide is using geometry extent provided by King.Oracle provider
to zoom on data in preview window.
King.Oracle provider will read extent in two ways. One is for
non-geodetic data it will read from spatial index ( which is updated
dynamically) and second for geodetic coordinate systems it will read
from Oracle SDO_GEOM_METADATA view. Usually in this view will be
[-180, -90] [180,90] for geodetic data so MapGuide
You can use Fdo2Fdo
to recalculate geometry extent and find correct SRID and insert or
update SDO_GEOM_METADATA view.
FDO has a concept of Spatial Context and every geometry in a layer
has a description to which Spatial Context it belongs.
Spatial Context is description of coordinate system (WKT), number of
dimensions, geometry extent and tolerance.
When reading Oracle tables King.Oracle provider will create one or
more Spatial Contexts which depends on number of used coordinate
If all geometry tables have same SRID it will be just one Spatial
Context. Important thing is that geometry extent is calculated based
on all layers in that Spatial Context. So you need to set correct
layer extents for every layer to be correctly displayed in preview
window of MapGuide.
Primary Key and Identity
King.Oracle provider will check if table has a primary key defined.
If primary key is found and it is single column with NUMERIC or
VARCHAR2 data type than it will be used as identity column for FDO
Feature class. FDO Feature class can be used without Identity for
viewing geometry data. If you want to be able to edit data in MapGuide or Map you need an Identity column.
You can use Fdo2Fdo
tool to create primary key and also to create primary key on Oracle
King.Oracle provider allows update, delete and insert of data
without identity column. For update you can set any filter
(geometry, attribute filter) or no filter at all.
Oracle Sequence "_FDOSEQ"
If FDO Feature class has primary key defined and if it is of type
NUMERIC than King.Oracle provider will also check for Oracle
Sequence to use for primary key column. Sequence has to have a name
like TableName_FDOSEQ to be used by provider.
For table named RAIL sequence name of sequence is RAIL_FDOSEQ.
This sequence will be used by provider during inserts to populate
value for identity column. If value for identity is not set during
insert than provider will use next value from sequence to insert a
When using Fdo2Fdo tool to
import data to Oracle it will create primary key and sequence if
source FDO Feature class has a identity of integer
You can use non-materialized and materialized Oracle Views with
King.Oracle provider. To use view you need to insert
SDO_GEOM_METADATA in same way as you would do for table. Also you
can create an primary key on non-materialized and
materialized Oracle Views.