2.7.7 Type 0 (Zero) Element

Type 0 (zero) elements are used to model geometry types that are not supported by Oracle Spatial and Graph, such as curves and splines. A type 0 element has an SDO_ETYPE value of 0. (See SDO_ELEM_INFO for information about the SDO_ETYPE.) Type 0 elements are not indexed by Oracle Spatial and Graph, and they are ignored by spatial functions and procedures.

Geometries with type 0 elements must contain at least one nonzero element, that is, an element with an SDO_ETYPE value that is not 0. The nonzero element should be an approximation of the unsupported geometry, and therefore it must have both:

• An SDO_ETYPE value associated with a geometry type supported by Spatial and Graph

• An SDO_INTERPRETATION value that is valid for the SDO_ETYPE value (see Table 2-2)

  (The SDO_INTERPRETATION value for the type 0 element can be any numeric value, and applications are responsible for determining the validity and significance of the value.)

The nonzero element is indexed by Spatial and Graph, and it will be returned by the spatial index.

The SDO_GTYPE value for a geometry containing a type 0 element must be set to the value for the geometry type of the nonzero element.

Figure 2-9 shows a geometry with two elements: a curve (unsupported geometry) and a rectangle (the nonzero element) that approximates the curve. The curve looks like the letter S, and the rectangle is represented by the dashed line.

Figure 2-9 Geometry with Type 0 (Zero) Element

Description of "Figure 2-9 Geometry with Type 0 (Zero) Element"

In the example shown in Figure 2-9:

• The SDO_GTYPE value for the geometry is 2003 (for a two-dimensional polygon).

• The SDO_ELEM_INFO array contains two triplets for this compound line string. For example, the triplets might be {(1,0,57), (11,1003,3)}. That is:

  Ordinate Starting Offset (SDO_STARTING_OFFSET)	Element Type (SDO_ETYPE)	Interpretation (SDO_INTERPRETATION)
  1	0	57
  11	1003	3

In this example:

• The type 0 element has an SDO_ETYPE value of 0.

• The nonzero element (rectangle) has an SDO_ETYPE value of 1003, indicating an exterior polygon ring.

• The nonzero element has an SDO_STARTING_OFFSET value of 11 because ordinate x6 is the eleventh ordinate in the geometry.

• The type 0 element has an SDO_INTERPRETATION value whose significance is application-specific. In this example, the SDO_INTERPRETATION value is 57.

• The nonzero element has an SDO_INTERPRETATION value that is valid for the SDO_ETYPE of 1003. In this example, the SDO_INTERPRETATION value is 3, indicating a rectangle defined by two points (lower-left and upper-right).

Example 2-14 shows a SQL statement that inserts the geometry with a type 0 element (similar to the geometry illustrated in Figure 2-9) into the database. In the SDO_ORDINATE_ARRAY structure, the curve is defined by points (6,6), (12,6), (9,8), (6,10), and (12,10), and the rectangle is defined by points (6,4) and (12,12).

INSERT INTO cola_markets VALUES(
  13,
  'type_zero_element_geom',
  SDO_GEOMETRY(
    2003,  -- two-dimensional polygon
    NULL,
    NULL,
    SDO_ELEM_INFO_ARRAY(1,0,57, 11,1003,3), -- 1st is type 0 element
    SDO_ORDINATE_ARRAY(6,6, 12,6, 9,8, 6,10, 12,10, 6,4, 12,12)
  )
);