Sdo_util.Getnumrings Documentation ?

Question

Hi,
Has sdo_util.getnumrings ever been documented anywhere? It's there in my 10g MDSYS schema, and seems to work as the name suggests, but seeing a smidge of documentation would be reassuring.
Maybe there's a secret decoder ring for the documentation (http://download.oracle.com/docs/html/B14255_01/toc.htm) that reveals all kinds of hidden utilities.
Thanks!
Matt

Answer 1

The SQL examples I gave were simplified and not correct in all cases. The reason for this is that the predicate:
where b.column_value in (1003,1005,2003,2005)
...does not discriminate between the ordinate offset, etype and interpretation triplet that is a standard entry for sdo_elem_info_array. So, if an ordinate offset was either 1003, 1005, 2003 or 2005 it would incorrectly add to the count of rings.
The way to correctly query the sdo_elem_info_array is via a SQL pivot as follows:
SELECT count(*) as ringcount
  FROM (SELECT e.id,
               e.etype,
               e.offset,
               e.interpretation
          FROM (SELECT trunc((rownum - 1) / 3,0) as id,
                       sum(case when mod(rownum,3) = 1 then sei.column_value else null end) as offset,
                       sum(case when mod(rownum,3) = 2 then sei.column_value else null end) as etype,
                       sum(case when mod(rownum,3) = 0 then sei.column_value else null end) as interpretation
                  FROM TABLE(SDO_GEOMETRY(2007,  -- two-dimensional multi-part polygon with hole
                                          NULL,
                                          NULL,
                                          SDO_ELEM_INFO_ARRAY(1,1005,2, 1,2,1, 5,2,2,
                                                             11,2005,2, 11,2,1, 15,2,2,
                                                             21,1005,2, 21,2,1, 25,2,2),
                                          SDO_ORDINATE_ARRAY(  6,10, 10,1, 14,10, 10,14,  6,10,
                                                              13,10, 10,2,  7,10, 10,13, 13,10,
                                                            106,110, 110,101, 114,110, 110,114,106,110)).sdo_elem_info
                            ) sei
                 GROUP BY trunc((rownum - 1) / 3,0)
                ) e
       ) i
WHERE i.etype in (1003,1005,2003,2005);To create your own function in case you are worried about use of an undocumented Oracle function using the above is fairly trivial:
create or replace Function GetNumRings( p_geometry in mdsys.sdo_geometry )
  Return Number Deterministic
Is
  v_ring_count number := 0;
Begin
  SELECT count(*) as ringcount
    INTO v_ring_count
    FROM (SELECT e.id,
                 e.etype,
                 e.offset,
                 e.interpretation
            FROM (SELECT trunc((rownum - 1) / 3,0) as id,
                         sum(case when mod(rownum,3) = 1 then sei.column_value else null end) as offset,
                         sum(case when mod(rownum,3) = 2 then sei.column_value else null end) as etype,
                         sum(case when mod(rownum,3) = 0 then sei.column_value else null end) as interpretation
                    FROM TABLE(p_geometry.sdo_elem_info) sei
                   GROUP BY trunc((rownum - 1) / 3,0)
                  ) e
         ) i
   WHERE i.etype in (1003,1005,2003,2005);
  Return v_ring_count;
End GetNumRings;
SHOW ERRORSAnd, testing it:
SELECT GetNumRings(NULL) As RingCount FROM DUAL;
RINGCOUNT
0
1 rows selected
SELECT GetNumRings(SDO_GEOMETRY(2001,NULL,SDO_POINT_TYPE(10,10,10),NULL,NULL)) As RingCount FROM DUAL;
RINGCOUNT
0
1 rows selected
SELECT GetNumRings(SDO_GEOMETRY(2002,NULL,NULL,SDO_ELEM_INFO_ARRAY(1,2,1),SDO_ORDINATE_ARRAY(1,1,10,10))) As RingCount FROM DUAL;
RINGCOUNT
0
1 rows selected
SELECT GetNumRings(SDO_GEOMETRY(2003,NULL,NULL,SDO_ELEM_INFO_ARRAY(1,1003,3),SDO_ORDINATE_ARRAY(1,1,10,10))) As RingCount FROM DUAL;
RINGCOUNT
1
1 rows selected
SELECT GetNumRings(SDO_GEOMETRY(2003,NULL,NULL,SDO_ELEM_INFO_ARRAY(1,1003,3,5,2003,3),SDO_ORDINATE_ARRAY(1,1,100,100,20,20,40,40))) As RingCount FROM DUAL;
RINGCOUNT
2
1 rows selected
SELECT GetNumRings(SDO_GEOMETRY(2007,  -- two-dimensional multi-part polygon with hole
                                NULL,
                                NULL,
                                SDO_ELEM_INFO_ARRAY(1,1005,2, 1,2,1, 5,2,2,
                                                   11,2005,2, 11,2,1, 15,2,2,
                                                   21,1005,2, 21,2,1, 25,2,2),
                                SDO_ORDINATE_ARRAY(  6,10, 10,1, 14,10, 10,14,  6,10,
                                                    13,10, 10,2,  7,10, 10,13, 13,10,
                                                   106,110, 110,101, 114,110, 110,114,106,110)
        as RingCount
  FROM DUAL;
RINGCOUNT
3
1 rows selectedNote that the function did not need exception handling for NULL or non-polygon geometries as the answer returned from the SQL is correct.
Hope this helps.
regards
Simon
Edited by: sgreener on Dec 21, 2008 5:34 PM to add function and call examples.