Slow performance for context index

Question

Hi, I'm just a newbie here in forum and I would like ask for your expertise about oracle context index. I have my sql and I'm using wild character for searching '%%' .
I used the sql below with a context index (ctxsys.context) in order to avoid full table scan for wild character searching.
SELECT BODY_ID
                    TITLE, trim(upper(title)) as title_sort,
                    SUM(JAN) as JAN,
                    SUM(FEB) as FEB,
                    SUM(MAR) as MAR,
                    SUM(APR) as APR,
                    SUM(MAY) as MAY,
                    SUM(JUN) as JUN,
                    SUM(JUL) as JUL,
                    SUM(AUG) as AUG,
                    SUM(SEP) as SEP,
                    SUM(OCT) as OCT,
                    SUM(NOV) as NOV,
                    SUM(DEC) AS DEC
                    FROM APP_REPCBO.CBO_TURNAWAY_REPORT
                    WHERE contains (BODY_ID,'%240103%') >0 and
PERIOD BETWEEN '1201' AND '1212'
                    GROUP BY BODY_ID, trim(upper(title))
But i was surprised that performance was very slow, and when I try this on explain plan time of performance almost consume 2 hours.
plan FOR succeeded.
PLAN_TABLE_OUTPUT
Plan hash value: 814472363
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1052K| 97M| | 805K (1)| 02:41:12 |
| 1 | HASH GROUP BY | | 1052K| 97M| 137M| 805K (1)| 02:41:12 |
|* 2 | TABLE ACCESS BY INDEX ROWID| CBO_TURNAWAY_REPORT | 1052K| 97M| | 782K (1)| 02:36:32 |
|* 3 | DOMAIN INDEX | CBO_REPORT_BID_IDX | | | | 663K (0)| 02:12:41 |
Predicate Information (identified by operation id):
2 - filter("PERIOD">='1201' AND "PERIOD"<='1212')
3 - access("CTXSYS"."CONTAINS"("BODY_ID",'%240103%')>0)
16 rows selected
oracle version: Oracle Database 11g Release 11.1.0.7.0 - 64bit Production
Thanks,
Zack

Answer 1

Hi Rod,
Thanks for the reply, yes I already made gather stats on that table, including rebuild index.
but its so strange when I use another body_id the performance will vary.
SQL> EXPLAIN PLAN FOR
2 SELECT BODY_ID
3 TITLE, trim(upper(title)) as title_sort,
4 SUM(JAN) as JAN,
5 SUM(FEB) as FEB,
6 SUM(MAR) as MAR,
7 SUM(APR) as APR,
8 SUM(MAY) as MAY,
9 SUM(JUN) as JUN,
10 SUM(JUL) as JUL,
11 SUM(AUG) as AUG,
12 SUM(SEP) as SEP,
13 SUM(OCT) as OCT,
14 SUM(NOV) as NOV,
15 SUM(DEC) as DEC
16 FROM WEB_REPCBO.CBO_TURNAWAY_REPORT
17 WHERE contains (BODY_ID,'%119915311%')> 0 and
18 PERIOD BETWEEN '1201' AND '1212'
19 GROUP BY BODY_ID, trim(upper(title));
SELECT * FROM TABLE (dbms_xplan.display);
Explained.
SQL>
Explained.
SQL>
PLAN_TABLE_OUTPUT
Plan hash value: 814472363
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 990 | 96030 | 1477 (1)| 00:00:18 |
| 1 | HASH GROUP BY | | 990 | 96030 | 1477 (1)| 00:00:18 |
|* 2 | TABLE ACCESS BY INDEX ROWID| CBO_TURNAWAY_REPORT | 990 | 96030 | 1475 (0)| 00:00:18 |
|* 3 | DOMAIN INDEX | CBO_REPORT_BID_IDX | | | 647 (0)| 00:00:08 |
Predicate Information (identified by operation id):
2 - filter("PERIOD">='1201' AND "PERIOD"<='1212')
3 - access("CTXSYS"."CONTAINS"("BODY_ID",'%119915311%')>0)
16 rows selected.