Poor performance when Distinct and Order By Used

Question

Hello,
I am getting an slow answer when I add Distinct and Order By to the query:
Without Distinct and Order By lasts 3.57 seconds; without Distinct and Order By lasts 28.15 seconds, which it's too much for our app.
The query is:
select distinct CC.acceso, CC.ext_acceso, TIT.TITULO_SALIDA
from (((Ocurrencias CT01 inner join
palabras p0 on (CT01.cod_palabra = p0.cod_palabra and p0.palabra like 'VENEZUELA%' AND p0.campo = 'AUTOR')) INNER JOIN
CENTRAL CC ON (CT01.ACCESO = CC.ACCESO AND CT01.EXT_ACCESO = CC.EXT_ACCESO))) inner join
codtit ctt on (CC.acceso = ctt.acceso and CC.ext_acceso = ctt.ext_acceso) inner join
titulos tit on (ctt.cod_titulo = tit.cod_titulo and ctt.portada = '1')
where CC.nivel_reg <> 's'
ORDER BY 3 ASC;
The query plan for the query WITH Distinct and Order By is:
Elapsed: 00:00:28.15
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=301 Card=47 Bytes=12220)
1 0 SORT (ORDER BY) (Cost=301 Card=47 Bytes=12220)
2 1 SORT (UNIQUE) (Cost=300 Card=47 Bytes=12220)
3 2 NESTED LOOPS (Cost=299 Card=47 Bytes=12220)
4 3 NESTED LOOPS (Cost=250 Card=49 Bytes=4165)
5 4 NESTED LOOPS (Cost=103 Card=49 Bytes=2989)
6 5 NESTED LOOPS (Cost=5 Card=49 Bytes=1960)
7 6 TABLE ACCESS (BY INDEX ROWID) OF 'PALABRAS' (TABLE) (Cost=3 Card=1 Bytes=19)
8 7 INDEX (RANGE SCAN) OF 'PALABRA' (INDEX (UNIQUE)) (Cost=2 Card=1)
9 6 INDEX (RANGE SCAN) OF 'PK_OCURRENCIAS' (INDEX (UNIQUE)) (Cost=2 Card=140 Bytes=2940)
10 5 TABLE ACCESS (BY INDEX ROWID) OF 'CENTRAL' (TABLE) (Cost=2 Card=1 Bytes=21)
11 10 INDEX (UNIQUE SCAN) OF 'PK_CENTRAL' (INDEX (UNIQUE)) (Cost=1 Card=1)
12 4 TABLE ACCESS (BY INDEX ROWID) OF 'CODTIT' (TABLE) (Cost=3 Card=1 Bytes=24)
13 12 INDEX (RANGE SCAN) OF 'PK_CODTIT' (INDEX (UNIQUE)) (Cost=2 Card=1)
14 3 TABLE ACCESS (BY INDEX ROWID) OF 'TITULOS' (TABLE) (Cost=1 Card=1 Bytes=175)
15 14 INDEX (UNIQUE SCAN) OF 'PK_TITULOS' (INDEX (UNIQUE)) (Cost=0 Card=1)
Statistics
154 recursive calls
0 db block gets
32070 consistent gets
1622 physical reads
0 redo size
305785 bytes sent via SQL*Net to client
2807 bytes received via SQL*Net from client
212 SQL*Net roundtrips to/from client
10 sorts (memory)
0 sorts (disk)
3149 rows processed
The query plan for the query WITHOUT Distinct and Order By is:
Elapsed: 00:00:03.57
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=299 Card=47 Bytes=12220)
1 0 NESTED LOOPS (Cost=299 Card=47 Bytes=12220)
2 1 NESTED LOOPS (Cost=250 Card=49 Bytes=4165)
3 2 NESTED LOOPS (Cost=103 Card=49 Bytes=2989)
4 3 NESTED LOOPS (Cost=5 Card=49 Bytes=1960)
5 4 TABLE ACCESS (BY INDEX ROWID) OF 'PALABRAS' (TABLE) (Cost=3 Card=1 Bytes=19)
6 5 INDEX (RANGE SCAN) OF 'PALABRA' (INDEX (UNIQUE)) (Cost=2 Card=1)
7 4 INDEX (RANGE SCAN) OF 'PK_OCURRENCIAS' (INDEX (UNIQUE)) (Cost=2 Card=140 Bytes=2940)
8 3 TABLE ACCESS (BY INDEX ROWID) OF 'CENTRAL' (TABLE) (Cost=2 Card=1 Bytes=21)
9 8 INDEX (UNIQUE SCAN) OF 'PK_CENTRAL' (INDEX (UNIQUE)) (Cost=1 Card=1)
10 2 TABLE ACCESS (BY INDEX ROWID) OF 'CODTIT' (TABLE) (Cost=3 Card=1 Bytes=24)
11 10 INDEX (RANGE SCAN) OF 'PK_CODTIT' (INDEX (UNIQUE)) (Cost=2 Card=1)
12 1 TABLE ACCESS (BY INDEX ROWID) OF 'TITULOS' (TABLE) (Cost=1 Card=1 Bytes=175)
13 12 INDEX (UNIQUE SCAN) OF 'PK_TITULOS' (INDEX (UNIQUE)) (Cost=0 Card=1)
Statistics
3376 recursive calls
0 db block gets
33443 consistent gets
1061 physical reads
0 redo size
313751 bytes sent via SQL*Net to client
2807 bytes received via SQL*Net from client
422 SQL*Net roundtrips to/from client
90 sorts (memory)
0 sorts (disk)
3149 rows processed
I would appreciate a lot if somebody can tell me how to improve the performance of the query with Distinct and Order By.
Thank you very much,
Icaro Alzuru C.

Answer 1

Hello,
I am getting an slow answer when I add Distinct and Order By to the query:
Without Distinct and Order By lasts 3.57 seconds; without Distinct and Order By lasts 28.15 seconds, which it's too much for our app.
The query is:
select distinct CC.acceso, CC.ext_acceso, TIT.TITULO_SALIDA
from (((Ocurrencias CT01 inner join
palabras p0 on (CT01.cod_palabra = p0.cod_palabra and p0.palabra like 'VENEZUELA%' AND p0.campo = 'AUTOR')) INNER JOIN
CENTRAL CC ON (CT01.ACCESO = CC.ACCESO AND CT01.EXT_ACCESO = CC.EXT_ACCESO))) inner join
codtit ctt on (CC.acceso = ctt.acceso and CC.ext_acceso = ctt.ext_acceso) inner join
titulos tit on (ctt.cod_titulo = tit.cod_titulo and ctt.portada = '1')
where CC.nivel_reg <> 's'
ORDER BY 3 ASC;
The query plan for the query WITH Distinct and Order By is:
Elapsed: 00:00:28.15
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=301 Card=47 Bytes=12220)
1 0 SORT (ORDER BY) (Cost=301 Card=47 Bytes=12220)
2 1 SORT (UNIQUE) (Cost=300 Card=47 Bytes=12220)
3 2 NESTED LOOPS (Cost=299 Card=47 Bytes=12220)
4 3 NESTED LOOPS (Cost=250 Card=49 Bytes=4165)
5 4 NESTED LOOPS (Cost=103 Card=49 Bytes=2989)
6 5 NESTED LOOPS (Cost=5 Card=49 Bytes=1960)
7 6 TABLE ACCESS (BY INDEX ROWID) OF 'PALABRAS' (TABLE) (Cost=3 Card=1 Bytes=19)
8 7 INDEX (RANGE SCAN) OF 'PALABRA' (INDEX (UNIQUE)) (Cost=2 Card=1)
9 6 INDEX (RANGE SCAN) OF 'PK_OCURRENCIAS' (INDEX (UNIQUE)) (Cost=2 Card=140 Bytes=2940)
10 5 TABLE ACCESS (BY INDEX ROWID) OF 'CENTRAL' (TABLE) (Cost=2 Card=1 Bytes=21)
11 10 INDEX (UNIQUE SCAN) OF 'PK_CENTRAL' (INDEX (UNIQUE)) (Cost=1 Card=1)
12 4 TABLE ACCESS (BY INDEX ROWID) OF 'CODTIT' (TABLE) (Cost=3 Card=1 Bytes=24)
13 12 INDEX (RANGE SCAN) OF 'PK_CODTIT' (INDEX (UNIQUE)) (Cost=2 Card=1)
14 3 TABLE ACCESS (BY INDEX ROWID) OF 'TITULOS' (TABLE) (Cost=1 Card=1 Bytes=175)
15 14 INDEX (UNIQUE SCAN) OF 'PK_TITULOS' (INDEX (UNIQUE)) (Cost=0 Card=1)
Statistics
154 recursive calls
0 db block gets
32070 consistent gets
1622 physical reads
0 redo size
305785 bytes sent via SQL*Net to client
2807 bytes received via SQL*Net from client
212 SQL*Net roundtrips to/from client
10 sorts (memory)
0 sorts (disk)
3149 rows processed
The query plan for the query WITHOUT Distinct and Order By is:
Elapsed: 00:00:03.57
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=299 Card=47 Bytes=12220)
1 0 NESTED LOOPS (Cost=299 Card=47 Bytes=12220)
2 1 NESTED LOOPS (Cost=250 Card=49 Bytes=4165)
3 2 NESTED LOOPS (Cost=103 Card=49 Bytes=2989)
4 3 NESTED LOOPS (Cost=5 Card=49 Bytes=1960)
5 4 TABLE ACCESS (BY INDEX ROWID) OF 'PALABRAS' (TABLE) (Cost=3 Card=1 Bytes=19)
6 5 INDEX (RANGE SCAN) OF 'PALABRA' (INDEX (UNIQUE)) (Cost=2 Card=1)
7 4 INDEX (RANGE SCAN) OF 'PK_OCURRENCIAS' (INDEX (UNIQUE)) (Cost=2 Card=140 Bytes=2940)
8 3 TABLE ACCESS (BY INDEX ROWID) OF 'CENTRAL' (TABLE) (Cost=2 Card=1 Bytes=21)
9 8 INDEX (UNIQUE SCAN) OF 'PK_CENTRAL' (INDEX (UNIQUE)) (Cost=1 Card=1)
10 2 TABLE ACCESS (BY INDEX ROWID) OF 'CODTIT' (TABLE) (Cost=3 Card=1 Bytes=24)
11 10 INDEX (RANGE SCAN) OF 'PK_CODTIT' (INDEX (UNIQUE)) (Cost=2 Card=1)
12 1 TABLE ACCESS (BY INDEX ROWID) OF 'TITULOS' (TABLE) (Cost=1 Card=1 Bytes=175)
13 12 INDEX (UNIQUE SCAN) OF 'PK_TITULOS' (INDEX (UNIQUE)) (Cost=0 Card=1)
Statistics
3376 recursive calls
0 db block gets
33443 consistent gets
1061 physical reads
0 redo size
313751 bytes sent via SQL*Net to client
2807 bytes received via SQL*Net from client
422 SQL*Net roundtrips to/from client
90 sorts (memory)
0 sorts (disk)
3149 rows processed
I would appreciate a lot if somebody can tell me how to improve the performance of the query with Distinct and Order By.
Thank you very much,
Icaro Alzuru C.