Extract SDO_GEOMETRY line vertices into a nested table column (in a query resultset)

All we need is an easy explanation of the problem, so here it is.

Oracle 18c:

In a related post, I demonstrated how to use the GetVertices() function and the Table() function to extract the vertices of an SDO_GEOMETRY line:

Select SDO_GEOMETRY line vertices as rows

select  
    a.line_id, b.id as vertex_id, b.x, b.y
from
    a_sdo_geometry_tbl a, 
    table(sdo_util.getvertices(a.shape)) b       --<<--Here

   LINE_ID  VERTEX_ID          X          Y
---------- ---------- ---------- ----------
         1          1 671539.685 4863324.18
         1          2 671595.050 4863343.17
         1          3 671614.014 4863350.34
         1          4 671622.204 4863353.53

         2          1 71534.5567 4863119.99
         2          2 671640.738 4863157.13
         2          3 671684.862 4863172.02

As a learning exercise, I want to create my own version of the GetVertices() function using PL/SQL.

I’m open to ideas about what sort of mechanism to use; any of the following would be fine:

  • Basic SQL
  • MODEL clause
  • Custom function

The point is, I want to learn how to extract the vertices and put them into a nested table column in a query, just like the GetVertices() function does.

SDO_UTIL.GETVERTICES

This function returns an object of MDSYS.VERTEX_SET_TYPE, which
consists of a table of objects of MDSYS.VERTEX_TYPE. Oracle Spatial
and Graph defines the type VERTEX_SET_TYPE as:

CREATE TYPE vertex_set_type as TABLE OF vertex_type;

Oracle Spatial and Graph defines the object type VERTEX_TYPE as:

CREATE TYPE vertex_type AS OBJECT
   (x   NUMBER,
    y   NUMBER,
    z   NUMBER,
    w   NUMBER,
    v5  NUMBER,
    v6  NUMBER,
    v7  NUMBER,
    v8  NUMBER,
    v9  NUMBER,
    v10 NUMBER,
    v11 NUMBER,
    id  NUMBER);

Note: The VERTEX_SET_TYPE and VERTEX_TYPE types are intended for use by
Oracle only. Do not use these types in column definitions or functions
that you create.


Question:

Is there a way to extract an SDO_GEOMETRY line’s vertices into a nested table column in a query — without using the GetVertices() function?
The output would be a query resultset, not a static table.


Hints:

The following functions might be useful:

PointN: Returns a point that is the nth vertex in the collection of vertices

GetNumVertices: Returns the number of vertices in the input geometry.

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

It seems like the only way to do this is by creating a custom type and a custom function:

CREATE TYPE vertex_type_cust AS object
(
  x  NUMBER,
  y  NUMBER,
  z  NUMBER,
  w  NUMBER,
  id NUMBER );

CREATE TYPE vertex_set_type_cust AS TABLE OF vertex_type_cust;

CREATE OR replace FUNCTION getvertices_cust(geometry mdsys.sdo_geometry)
  RETURN vertex_set_type_cust
IS
  i      NUMBER;
  dims   NUMBER;
  coords NUMBER;
  result vertex_set_type_cust;
  dim mdsys.sdo_dim_array;
  is_zero BOOLEAN;
  etype   NUMBER;
BEGIN
  result := vertex_set_type_cust();
  -- handle the POINT case here
  IF (geometry.sdo_ordinates IS NULL) THEN
    result.extend;
    result(1) := vertex_type_cust(geometry.sdo_point.x, geometry.sdo_point.y, geometry.sdo_point.z,NULL,1);
    RETURN result;
  END IF;
  -- all other cases here
  coords := geometry.sdo_ordinates.count;
  dims := geometry.get_dims;
  IF (dims = 0) THEN
    RETURN result;
  END IF;
  coords := coords/dims;
  FOR i          IN 0 .. coords-1
  LOOP
    result.extend;
    IF (dims = 2) THEN
      result(i+1) := vertex_type_cust(geometry.sdo_ordinates(2*i+1), geometry.sdo_ordinates(2*i+2), NULL,NULL,i+1);
    ELSIF (dims = 3) THEN
      result(i+1) := vertex_type_cust(geometry.sdo_ordinates(3*i+1), geometry.sdo_ordinates(3*i+2), geometry.sdo_ordinates(3*i+3) ,NULL,i+1);
    ELSIF (dims = 4) THEN
      result(i+1) := vertex_type_cust(geometry.sdo_ordinates(4*i+1), geometry.sdo_ordinates(4*i+2), geometry.sdo_ordinates(4*i+3), geometry.sdo_ordinates(4*i+4), i+1);
    END IF;
  END LOOP;
  RETURN result;
END;

Test data:

create table a_sdo_geometry_tbl (line_id integer, shape mdsys.sdo_geometry);

insert into a_sdo_geometry_tbl (line_id, shape) 
values (1, sdo_geometry (2002, null, null, sdo_elem_info_array (1,2,1), 
    sdo_ordinate_array (671539.6852734378,4863324.181436138, 671595.0500703361,4863343.166556185, 671614.013553706,4863350.343483042, 671622.2044153381,4863353.525396131))  );

insert into a_sdo_geometry_tbl (line_id, shape) 
values (2, sdo_geometry (2002, null, null, sdo_elem_info_array (1,2,1), 
    sdo_ordinate_array (71534.5567096211,4863119.991809748, 671640.7384688659,4863157.132745253, 671684.8621150404,4863172.022995591))  );

insert into a_sdo_geometry_tbl (line_id, shape) 
values (3, sdo_geometry (2002, null, null, sdo_elem_info_array (1,2,1), 
    sdo_ordinate_array (671622.2044153381,4863353.525396131, 671633.3267164109,4863357.846229106, 671904.0614077691,4863451.286166754))  );

insert into a_sdo_geometry_tbl (line_id, shape) 
values (4, sdo_geometry (2002, null, null, sdo_elem_info_array (1,2,1), 
    sdo_ordinate_array (671684.8620521119,4863172.022995591, 671892.1496144319,4863244.141440067, 671951.2156571196,4863264.824310392, 671957.4471461186,4863266.847617676, 671966.8243856924,4863269.146632658))  )

Use the custom function:

select
    a.line_id,
    b.id as vertex_id,
    b.x, 
    b.y
from
    a_sdo_geometry_tbl a
cross join
    table(getvertices_cust(a.shape)) b  
order by 
    a.line_id, b.id;

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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