No rows returned by spatial query wrapped in SELECT * FROM ...

Question

Hi,
I'm getting some really weird behaviour when running a sub query with SDO_EQUAL. The SDO_EQUAL query on its own works fine, but if I wrap it in SELECT * FROM then I get no results. If I wrap SDO_ANYINTERACT in SELECT * FROM then I get the expected result.
It looks like the spatial index is used when running the regular SDO_EQUAL query, but not when wrapped in SELECT * FROM. Weird. The spatial index is also not used when SDO_ANYINTERACT is wrapped in SELECT * FROM... so I'm not sure why that returns the right answer.
I am getting this problem on 11.2.0.2 on Red Hat Linux 64bit and 11.2.0.1 on Windows XP 32bit (that's all the 11g versions I've tried). The query works as expected on 10.2.0.5 on Windows Server 2003 64bit.
Any ideas?
Confused in Dublin (John)
Test case...SQL>
SQL> -- Create a table and insert the same geometry twice
SQL> DROP TABLE sdo_equal_query_test;
Table dropped.
SQL> CREATE TABLE sdo_equal_query_test (
  2  id NUMBER,
  3  geometry SDO_GEOMETRY);
Table created.
SQL>
SQL> INSERT INTO sdo_equal_query_test VALUES (1,
  2  SDO_GEOMETRY(3003, 81989, NULL, SDO_ELEM_INFO_ARRAY(1, 1003, 1),
  3  SDO_ORDINATE_ARRAY(1057.39, 1048.23, 4, 1057.53, 1046.04, 4, 1057.67, 1043.94, 4, 1061.17, 1044.60, 5, 1060.95, 1046.49, 5, 1060.81, 1047.78, 5, 1057.39, 1048.23, 4)));
1 row created.
SQL>
SQL> INSERT INTO sdo_equal_query_test VALUES (2,
  2  SDO_GEOMETRY(3003, 81989, NULL, SDO_ELEM_INFO_ARRAY(1, 1003, 1),
  3  SDO_ORDINATE_ARRAY(1057.39, 1048.23, 4, 1057.53, 1046.04, 4, 1057.67, 1043.94, 4, 1061.17, 1044.60, 5, 1060.95, 1046.49, 5, 1060.81, 1047.78, 5, 1057.39, 1048.23, 4)));
1 row created.
SQL>
SQL> -- Setup metadata
SQL> DELETE FROM user_sdo_geom_metadata WHERE table_name = 'SDO_EQUAL_QUERY_TEST';
1 row deleted.
SQL> INSERT INTO user_sdo_geom_metadata VALUES ('SDO_EQUAL_QUERY_TEST','GEOMETRY',
  2  SDO_DIM_ARRAY(SDO_DIM_ELEMENT('X', 0, 100000, .0001), SDO_DIM_ELEMENT('Y', 0, 100000, .0001), SDO_DIM_ELEMENT('Z', -100, 4000, .0001))
  3  ,81989);
1 row created.
SQL>
SQL> -- Create spatial index
SQL> DROP INDEX sdo_equal_query_test_spind;
DROP INDEX sdo_equal_query_test_spind
ERROR at line 1:
ORA-01418: specified index does not exist
SQL> CREATE INDEX sdo_equal_query_test_spind ON sdo_equal_query_test(geometry) INDEXTYPE IS MDSYS.SPATIAL_INDEX;
Index created.
SQL>
SQL> -- Ensure data is valid
SQL> SELECT sdo_geom.validate_geometry_with_context(sdo_cs.make_2d(geometry), 0.0001) is_valid
  2  FROM sdo_equal_query_test;
IS_VALID
TRUE
TRUE
2 rows selected.
SQL>
SQL> -- Check query results using sdo_equal
SQL> SELECT b.id
  2  FROM sdo_equal_query_test a, sdo_equal_query_test b
  3  WHERE a.id = 1
  4  AND b.id != a.id
  5  AND sdo_equal(a.geometry, b.geometry) = 'TRUE';
        ID
         2
1 row selected.
SQL>
SQL> -- Check query results using sdo_equal wrapped in SELECT * FROM
SQL> -- Results should be the same as above, but... no rows selected
SQL> SELECT * FROM (
  2       SELECT b.id
  3       FROM sdo_equal_query_test a, sdo_equal_query_test b
  4       WHERE a.id = 1
  5       AND b.id != a.id
  6       AND sdo_equal(a.geometry, b.geometry) = 'TRUE'
  7  );
no rows selected
SQL>
SQL> -- So that didn't work.  Now try sdo_anyinteract... this works ok
SQL> SELECT * FROM (
  2       SELECT b.id
  3       FROM sdo_equal_query_test a, sdo_equal_query_test b
  4       WHERE a.id = 1
  5       AND b.id != a.id
  6       AND sdo_anyinteract(a.geometry, b.geometry) = 'TRUE'
  7  );
        ID
         2
1 row selected.
SQL>
SQL> -- Now try a scalar query
SQL> SELECT * FROM (
  2       SELECT b.id
  3       FROM sdo_equal_query_test a, sdo_equal_query_test b
  4       WHERE a.id = 1
  5       AND b.id != a.id
  6  );
        ID
         2
1 row selected.
SQL> spool offHere's the explain plan for the query that works. Note that the spatial index is used.
SQL> EXPLAIN PLAN FOR
  2  SELECT b.id
  3  FROM sdo_equal_query_test a, sdo_equal_query_test b
  4  WHERE a.id = 1
  5  AND b.id != a.id
  6  AND sdo_equal(a.geometry, b.geometry) = 'TRUE';
Explained.
SQL> @?/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 3529470109
| Id  | Operation                     | Name                       | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT              |                            |     1 |  7684 |     3   (0)| 00:00:01 |
|   1 |  RESULT CACHE                 | f5p63r46pbzty4sr45td1uv5g8 |       |       |            |       |
|   2 |   NESTED LOOPS                |                            |     1 |  7684 |     3   (0)| 00:00:01 |
|*  3 |    TABLE ACCESS FULL          | SDO_EQUAL_QUERY_TEST       |     1 |  3836 |     3   (0)| 00:00:01 |
|*  4 |    TABLE ACCESS BY INDEX ROWID| SDO_EQUAL_QUERY_TEST       |     1 |  3848 |     3   (0)| 00:00:01 |
|*  5 |     DOMAIN INDEX              | SDO_EQUAL_QUERY_TEST_SPIND |       |       |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   3 - filter("B"."ID"!=1)
   4 - filter("A"."ID"=1 AND "B"."ID"!="A"."ID")
   5 - access("MDSYS"."SDO_EQUAL"("A"."GEOMETRY","B"."GEOMETRY")='TRUE')
..... other stuff .....     Here's the explain plan for the query that does not work. Note that the spatial index is not used.
SQL> EXPLAIN PLAN FOR
  2  SELECT * FROM (
  3     SELECT b.id
  4     FROM sdo_equal_query_test a, sdo_equal_query_test b
  5     WHERE a.id = 1
  6     AND b.id != a.id
  7     AND sdo_equal(a.geometry, b.geometry) = 'TRUE'
  8  );
Explained.
SQL> @?/rdbms/admin/utlxpls.sql
PLAN_TABLE_OUTPUT
Plan hash value: 1024466006
| Id  | Operation           | Name                       | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT    |                            |     1 |  7684 |     6   (0)| 00:00:01 |
|   1 |  RESULT CACHE       | 2sd35wrcw3jr411bcg3sz161f6 |       |       |            |          |
|   2 |   NESTED LOOPS      |                            |     1 |  7684 |     6   (0)| 00:00:01 |
|*  3 |    TABLE ACCESS FULL| SDO_EQUAL_QUERY_TEST       |     1 |  3836 |     3   (0)| 00:00:01 |
|*  4 |    TABLE ACCESS FULL| SDO_EQUAL_QUERY_TEST       |     1 |  3848 |     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   3 - filter("B"."ID"!=1)
   4 - filter("A"."ID"=1 AND "B"."ID"!="A"."ID" AND
              "MDSYS"."SDO_EQUAL"("A"."GEOMETRY","B"."GEOMETRY")='TRUE')
..... other stuff .....               

Answer 1

That looks like a bug to me. As a workaround, you can materialize the inline view by adding rownum>0. Please see the reproduction and workaround below.
SCOTT@orcl_11gR2> SELECT *
  2  FROM   (SELECT b.id
  3            FROM   sdo_equal_query_test a, sdo_equal_query_test b
  4            WHERE  a.id = 1
  5            AND    b.id != a.id
  6            AND    sdo_equal (a.geometry, b.geometry) = 'TRUE')
  7  /
no rows selected
Execution Plan
Plan hash value: 1024466006
| Id  | Operation          | Name                 | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT   |                      |     1 |  7676 |     6   (0)| 00:00:01 |
|   1 |  NESTED LOOPS      |                      |     1 |  7676 |     6   (0)| 00:00:01 |
|*  2 |   TABLE ACCESS FULL| SDO_EQUAL_QUERY_TEST |     1 |  3832 |     3   (0)| 00:00:01 |
|*  3 |   TABLE ACCESS FULL| SDO_EQUAL_QUERY_TEST |     1 |  3844 |     3   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - filter("B"."ID"<>1)
   3 - filter("A"."ID"=1 AND "B"."ID"<>"A"."ID" AND
              "MDSYS"."SDO_EQUAL"("A"."GEOMETRY","B"."GEOMETRY")='TRUE')
Note
   - dynamic sampling used for this statement (level=2)
SCOTT@orcl_11gR2> SELECT *
  2  FROM   (SELECT b.id
  3            FROM   sdo_equal_query_test a, sdo_equal_query_test b
  4            WHERE  a.id = 1
  5            AND    b.id != a.id
  6            AND    sdo_equal (a.geometry, b.geometry) = 'TRUE'
  7            AND    ROWNUM > 0)
  8  /
        ID
         2
1 row selected.
Execution Plan
Plan hash value: 2329953927
| Id  | Operation                       | Name                       | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT                |                            |     1 |    13 |     3   (0)| 00:00:01 |
|   1 |  VIEW                           |                            |     1 |    13 |     3   (0)| 00:00:01 |
|   2 |   COUNT                         |                            |       |       |            |          |
|*  3 |    FILTER                       |                            |       |       |            |          |
|   4 |     NESTED LOOPS                |                            |     1 |  7676 |     3   (0)| 00:00:01 |
|*  5 |      TABLE ACCESS FULL          | SDO_EQUAL_QUERY_TEST       |     1 |  3832 |     3   (0)| 00:00:01 |
|*  6 |      TABLE ACCESS BY INDEX ROWID| SDO_EQUAL_QUERY_TEST       |     1 |  3844 |     3   (0)| 00:00:01 |
|*  7 |       DOMAIN INDEX              | SDO_EQUAL_QUERY_TEST_SPIND |       |       |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   3 - filter(ROWNUM>0)
   5 - filter("B"."ID"<>1)
   6 - filter("A"."ID"=1 AND "B"."ID"<>"A"."ID")
   7 - access("MDSYS"."SDO_EQUAL"("A"."GEOMETRY","B"."GEOMETRY")='TRUE')
Note
   - dynamic sampling used for this statement (level=2)
SCOTT@orcl_11gR2>