Connect by prior subquery - performance problem

Question

Hello,
I have some data which is organized in a folder tree. The requeriement is to be able to search from any subfolder and down.
/Documents
___Folder A
______Doc A
______Doc B
___Folder B
______Doc C
______Doc D
The folder structure is defined in a table called CORNERS where the records(=folders) has a ID/PARENTID relationsship to describe the folder structure.
Another table, called MASTER, contains the main content. Each item has a CORNERID value which defined in which subfolder the document is located.
MASTER
ID CORNERID TITLE INDEX_URL
100 2 Doc A http://xxx/yy.com
101 2 Doc B http://xxz/yy.com
102 3 Doc C http://xyz/yy.com
103 3 Doc D http://xyz/zz.com
CORNERS
ID PARENTID NAME
1 Documents
2 1 Folder A
3 1 Folder B
MASTER table has ~50000 records
CORNERS has ~900 records.
Analyzed nighly and stats are fresh.
Indexes defined:
CORNERS_ID_PARENT_IDX corners(id,parentid)
CORNERS_PARENT_ID_IDX corners(parentid,id)
MASTER_ID_CORNERID_IDX master(id,cornerid)
MASTER_CORNERID_ID_IDX master(cornerid,id)
Oracle Text index (URL based) on MASTER.INDEX_URL
Foreign key defined:
MASTER.CORNERID references CORNERS.ID
If I do a search without involving the hierarchy, then the search runs pretty fast:
SQL> SELECT COUNT(*) FROM (SELECT a.id, a.cornerid FROM MASTER a WHERE (CONTAINS(title,'$ADS AND {S} AND $PARAMETER',2) > 1 OR CONTAINS(index_url,'$ADS AND {S} AND $PARAMETER',1) > 1) );
COUNT(*)
5125
Elapsed: 00:00:00.14
Execution Plan
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=1354 Card=1 Bytes=15
8)
1 0 SORT (AGGREGATE)
2 1 TABLE ACCESS (BY INDEX ROWID) OF 'MASTER' (Cost=1354 Car
d=758 Bytes=119764)
3 2 BITMAP CONVERSION (TO ROWIDS)
4 3 BITMAP OR
5 4 BITMAP CONVERSION (FROM ROWIDS)
6 5 SORT (ORDER BY)
7 6 DOMAIN INDEX OF 'MASTER_TITLE_IDX' (Cost=470)
8 4 BITMAP CONVERSION (FROM ROWIDS)
9 8 SORT (ORDER BY)
10 9 DOMAIN INDEX OF 'MASTER_IDX' (Cost=650)
Statistics
1462 recursive calls
0 db block gets
5507 consistent gets
347 physical reads
0 redo size
380 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
2 sorts (memory)
0 sorts (disk)
1 rows processed
SQL>
BUT, if I add a subquery to limit the search to a certain folder tree (which includes ~200 nodes), then the performance is really badly affected. The subquery itself runs fast - around 0.07 seconds, but together with the rest of the query the preformance is really bad:
SQL> SELECT COUNT(*) FROM (SELECT a.id, a.cornerid FROM MASTER a WHERE (CONTAINS(title,'$ADS AND {S} AND $PARAMETER',2) > 1 OR CONTAINS(index_url,'$ADS AND {S} AND $PARAMETER',1) > 1) AND cornerid IN ( SELECT ID FROM corners START WITH id = 2434 CONNECT BY PRIOR id = parentid) );
COUNT(*)
942
Elapsed: 00:00:01.83
Execution Plan
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=118 Card=1 Bytes=175
1 0 SORT (AGGREGATE)
2 1 TABLE ACCESS (BY INDEX ROWID) OF 'MASTER' (Cost=19 Card=
1 Bytes=162)
3 2 NESTED LOOPS (Cost=118 Card=8 Bytes=1400)
4 3 VIEW OF 'VW_NSO_1' (Cost=2 Card=6 Bytes=78)
5 4 SORT (UNIQUE)
6 5 CONNECT BY (WITH FILTERING)
7 6 NESTED LOOPS
8 7 INDEX (UNIQUE SCAN) OF 'SYS_C002969' (UNIQUE
) (Cost=1 Card=1 Bytes=4)
9 7 TABLE ACCESS (BY USER ROWID) OF 'CORNERS'
10 6 NESTED LOOPS
11 10 BUFFER (SORT)
12 11 CONNECT BY PUMP
13 10 INDEX (RANGE SCAN) OF 'CORNERS_PARENT_ID_IDX
' (NON-UNIQUE) (Cost=2 Card=6 Bytes=48)
14 3 INDEX (RANGE SCAN) OF 'MASTER_CORNERID_ID_IDX' (NON-
UNIQUE) (Cost=1 Card=38)
Statistics
29267 recursive calls
0 db block gets
55414 consistent gets
140 physical reads
0 redo size
380 bytes sent via SQL*Net to client
503 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
12 sorts (memory)
0 sorts (disk)
1 rows processed
I've tried an alternative syntax, instead of the IN clause like this:
SELECT COUNT(*) FROM (
WITH folders AS (
SELECT ID
FROM CORNERS
START WITH ID=2434
CONNECT BY PRIOR ID= PARENTID
SELECT a.id
FROM MASTER a, folders b
WHERE a.cornerid = b.id
AND CONTAINS(index_url,'$ADS AND {S} AND $PARAMETER',1) > 1);
It does runfaster, but still takes around 1 second.
Any suggestion on how to make this run faster!?
Thanks in advance!
-Mats

Answer 1

how long does it takes to complete the query?