18.6 SDO_FILTER

Format

SDO_FILTER(geometry1, geometry2, param);

Description

Uses the spatial index to identify either the set of spatial objects that are likely to interact spatially with a given object (such as an area of interest), or pairs of spatial objects that are likely to interact spatially. Objects interact spatially if they are not disjoint.

This operator performs only a primary filter operation. The secondary filtering operation, performed by the SDO_RELATE operator, can be used to determine with certainty if objects interact spatially.

Keywords and Parameters

Value Description

geometry1

Specifies a geometry column in a table. The column must be spatially indexed. Data type is SDO_GEOMETRY.

geometry2

Specifies either a geometry from a table or a transient instance of a geometry. (Specified using a bind variable or SDO_GEOMETRY constructor.) Data type is SDO_GEOMETRY.

param

Optionally specifies either or both of the min_resolution and max_resolution keywords. Data type is VARCHAR2.

The min_resolution keyword includes only geometries for which at least one side of the geometry's MBR is equal to or greater than the specified value. For example, min_resolution=10 includes only geometries for which the width or the height (or both) of the geometry's MBR is at least 10. (This keyword can be used to exclude geometries that are too small to be of interest.)

The max_resolution keyword includes only geometries for which at least one side of the geometry's MBR is less than or equal to the specified value. For example, max_resolution=10 includes only geometries for which the width or the height (or both) of the geometry's MBR is less than or equal to 10. (This keyword can be used to exclude geometries that are too large to be of interest.)

Returns

The expression SDO_FILTER(geometry1,geometry2) = 'TRUE' evaluates to TRUE for object pairs that are non-disjoint, and FALSE otherwise.

Usage Notes

The SDO_FILTER operator must always be used in a WHERE clause and the condition that includes the operator should be an expression of the form SDO_FILTER(arg1, arg2) = 'TRUE'. (The expression must not equate to any value other than 'TRUE'.)

geometry2 can come from a table or be a transient SDO_GEOMETRY object, such as a bind variable or SDO_GEOMETRY constructor.

  • If the geometry2 column is not spatially indexed, the operator indexes the query window in memory and performance is very good.

  • If two or more geometries from geometry2 are passed to the operator, the ORDERED optimizer hint must be specified, and the table in geometry2 must be specified first in the FROM clause.

If geometry1 and geometry2 are based on different coordinate systems, geometry2 is temporarily transformed to the coordinate system of geometry1 for the operation to be performed, as described in Different Coordinate Systems for Geometries with Operators and Functions.

Note:

If the DBMS_RLS.ADD_POLICY procedure has been used to add a fine-grained access control policy to a table or view, and if the specified policy function uses a spatial operator, the operator must be SDO_FILTER. No other spatial operators are supported in that context.

For information about 3D support with spatial operators (which operators do and do not consider all three dimensions in their computations), see Three-Dimensional Spatial Objects.

Examples

The following example selects the geometries that are likely to interact with a query window (here, a rectangle with lower-left, upper-right coordinates 4,6, 8,8). (The example uses the definitions and data described in Simple Example: Inserting_ Indexing_ and Querying Spatial Data and illustrated in Figure 2-1.)

SELECT c.mkt_id, c.name
  FROM cola_markets c
  WHERE SDO_FILTER(c.shape,
    SDO_GEOMETRY(2003, NULL, NULL,
      SDO_ELEM_INFO_ARRAY(1,1003,3),
      SDO_ORDINATE_ARRAY(4,6, 8,8))
    ) = 'TRUE';
 
    MKT_ID NAME                                                                 
---------- --------------------------------                                     
         2 cola_b                                                               
         1 cola_a                                                               
         4 cola_d 

The following example is the same as the preceding example, except that it includes only geometries where at least one side of the geometry's MBR is equal to or greater than 4.1. In this case, only cola_a and cola_b are returned, because their MBRs have at least one side with a length greater than or equal to 4.1. The circle cola_d is excluded, because its MBR is a square whose sides have a length of 4.

SELECT c.mkt_id, c.name
  FROM cola_markets c
  WHERE SDO_FILTER(c.shape,
    SDO_GEOMETRY(2003, NULL, NULL,
      SDO_ELEM_INFO_ARRAY(1,1003,3),
      SDO_ORDINATE_ARRAY(4,6, 8,8)),
    'min_resolution=4.1'
    ) = 'TRUE';
 
    MKT_ID NAME                                                                 
---------- --------------------------------                                     
         2 cola_b                                                               
         1 cola_a 

The following example selects the GID values from the POLYGONS table where the GEOMETRY column objects are likely to interact spatially with the GEOMETRY column object in the QUERY_POLYS table that has a GID value of 1.

SELECT A.gid 
  FROM Polygons A, query_polys B 
  WHERE B.gid = 1 
  AND SDO_FILTER(A.Geometry, B.Geometry) = 'TRUE';

The following example selects the GID values from the POLYGONS table where the GEOMETRY column object is likely to interact spatially with the geometry stored in the aGeom variable.

Select A.Gid
  FROM Polygons A 
  WHERE SDO_FILTER(A.Geometry, :aGeom) = 'TRUE';

The following example selects the GID values from the POLYGONS table where the GEOMETRY column object is likely to interact spatially with the specified rectangle having the lower-left coordinates (x1,y1) and the upper-right coordinates (x2, y2).

Select A.Gid 
  FROM Polygons A 
  WHERE SDO_FILTER(A.Geometry, sdo_geometry(2003,NULL,NULL,
                                   sdo_elem_info_array(1,1003,3),
                                   sdo_ordinate_array(x1,y1,x2,y2))
                   ) = 'TRUE';

The following example selects the GID values from the POLYGONS table where the GEOMETRY column object is likely to interact spatially with any GEOMETRY column object in the QUERY_POLYS table. In this example, the ORDERED optimizer hint is used and the QUERY_POLYS (geometry2) table is specified first in the FROM clause, because multiple geometries from geometry2 are involved (see the Usage Notes).

SELECT /*+ ORDERED */
  A.gid 
  FROM query_polys B, polygons A 
  WHERE SDO_FILTER(A.Geometry, B.Geometry) = 'TRUE';

Related Topics