XMLType index supporting position in XPath

Question

I would like to know if it is possible to create index which will support position function in XPath.
For example:
Xpath:
select extractValue(p.pack_content,'/Data/Contractors/Contractor[278]/PermissionNumber')
from packages p;
The table packages is based on the schema and it is created by the statement:
CREATE TABLE packages
(pack_id NUMBER primary key,
pack_content XMLType
XMLTYPE COLUMN pack_content
XMLSCHEMA "http://www.example.com/example" ELEMENT "Data"
VARRAY pack_content."XMLDATA"."Contractors"."Contractor"
STORE AS TABLE pkg_contractors
((PRIMARY KEY (NESTED_TABLE_ID, SYS_NC_ARRAY_INDEX$))
ORGANIZATION INDEX OVERFLOW);
What kind of indexes should I create?
Grzegorz.

Answer 1

Just a stupid example to see if it could be done (not that it works);
Does it make any sense ?
No idea if this will work for you, you should further test it
SQL> select * from v$version;
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - Prod
PL/SQL Release 10.2.0.3.0 - Production
CORE    10.2.0.3.0      Production
TNS for 32-bit Windows: Version 10.2.0.3.0 - Production
NLSRTL Version 10.2.0.3.0 - Production
5 rows selected.
SQL> create table temp
  2  (lclob xmltype)
  3  ;
Table created.
SQL> insert into temp
  2  values('<itemMaster>
  3  <itemNumber>001000222</itemNumber>
  4  <itemDesc>HGR REUSE BX FOR HANGERRTNS </itemDesc>
  5  <paltSize>1</paltSize>
  6  <stdUOM>1</stdUOM>
  7  <shflfUOM>1</shflfUOM>
  8  <aliases>
  9  <upcCode>123456</upcCode>
10  <upcCode>490010002222</upcCode>
11  </aliases>
12  </itemMaster>
13  ')
14  ;
1 row created.
SQL> commit;
Commit complete.
SQL> select extractvalue(lclob,'/itemMaster/aliases/upcCode[position()=2]') from temp;
EXTRACTVALUE(LCLOB,'/ITEMMASTER/ALIASES/UPCCODE[POSITION()=2]')
490010002222
1 row selected.
SQL> set autotrace on
SQL> select extractvalue(lclob,'/itemMaster/aliases/upcCode[position()=2]') from temp;
EXTRACTVALUE(LCLOB,'/ITEMMASTER/ALIASES/UPCCODE[POSITION()=2]')
490010002222
1 row selected.
Execution Plan
Plan hash value: 1896031711
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |  2002 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| TEMP |     1 |  2002 |     3   (0)| 00:00:01 |
Note
   - dynamic sampling used for this statement
Statistics
          0  recursive calls
          0  db block gets
          7  consistent gets
          0  physical reads
          0  redo size
        476  bytes sent via SQL*Net to client
        385  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
SQL> create index pos_idx on temp
  2  (extractvalue(lclob,'/itemMaster/aliases/upcCode[position()]'));
Index created.
SQL> select extractvalue(lclob,'/itemMaster/aliases/upcCode[position()=2]') from temp;
EXTRACTVALUE(LCLOB,'/ITEMMASTER/ALIASES/UPCCODE[POSITION()=2]')
490010002222
1 row selected.
Execution Plan
Plan hash value: 1896031711
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |     1 |  2002 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| TEMP |     1 |  2002 |     3   (0)| 00:00:01 |
Note
   - dynamic sampling used for this statement
Statistics
         19  recursive calls
          0  db block gets
         19  consistent gets
          0  physical reads
          0  redo size
        476  bytes sent via SQL*Net to client
        385  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
SQL> begin  dbms_stats.set_table_stats
  2  ( ownname => 'MARCO'
  3  , tabname => 'TEMP'
  4  , numrows => 50000000  , numblks => 1200000  );
  5  end;
  6  /
PL/SQL procedure successfully completed.
SQL> select extractvalue(lclob,'/itemMaster/aliases/upcCode[position()=1]') from temp;
EXTRACTVALUE(LCLOB,'/ITEMMASTER/ALIASES/UPCCODE[POSITION()=1]')
123456
1 row selected.
Execution Plan
Plan hash value: 1896031711
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT  |      |    50M|  4768M|   265K  (2)| 00:53:04 |
|   1 |  TABLE ACCESS FULL| TEMP |    50M|  4768M|   265K  (2)| 00:53:04 |
Statistics
          8  recursive calls
          0  db block gets
          9  consistent gets
          0  physical reads
          0  redo size
        470  bytes sent via SQL*Net to client
        385  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processedMessage was edited by:
mgralike