What is the best way to replace the Inline Views for better performance ?

Question

Hi,
I am using Oracle 9i ,
What is the best way to replace the Inline Views for better performance. I see there are lot of performance lacking with Inline views in my queries.
Please suggest.
Raj

Answer 1

WITH plus /*+ MATERIALIZE */ hint can do good to you.
see below the test case.
SQL> create table hx_my_tbl as select level id, 'karthick' name from dual connect by level <= 5
2 /
Table created.
SQL> insert into hx_my_tbl select level id, 'vimal' name from dual connect by level <= 5
2 /
5 rows created.
SQL> create index hx_my_tbl_idx on hx_my_tbl(id)
2 /
Index created.
SQL> commit;
Commit complete.
SQL> exec dbms_stats.gather_table_stats(user,'hx_my_tbl',cascade=>true)
PL/SQL procedure successfully completed.
Now this a normal inline view
SQL> select a.id, b.id, a.name, b.name
2 from (select id, name from hx_my_tbl where id = 1) a,
3 (select id, name from hx_my_tbl where id = 1) b
4 where a.id = b.id
5 and a.name <> b.name
6 /
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=7 Card=2 Bytes=48)
1 0 HASH JOIN (Cost=7 Card=2 Bytes=48)
2 1 TABLE ACCESS (BY INDEX ROWID) OF 'HX_MY_TBL' (TABLE) (Cost=3 Card=2 Bytes=24)
3 2 INDEX (RANGE SCAN) OF 'HX_MY_TBL_IDX' (INDEX) (Cost=1 Card=2)
4 1 TABLE ACCESS (BY INDEX ROWID) OF 'HX_MY_TBL' (TABLE) (Cost=3 Card=2 Bytes=24)
5 4 INDEX (RANGE SCAN) OF 'HX_MY_TBL_IDX' (INDEX) (Cost=1 Card=2)
Now i use the with with the materialize hint
SQL> with my_view as (select /*+ MATERIALIZE */ id, name from hx_my_tbl where id = 1)
2 select a.id, b.id, a.name, b.name
3 from my_view a,
4 my_view b
5 where a.id = b.id
6 and a.name <> b.name
7 /
Execution Plan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=8 Card=1 Bytes=46)
1 0 TEMP TABLE TRANSFORMATION
2 1 LOAD AS SELECT
3 2 TABLE ACCESS (BY INDEX ROWID) OF 'HX_MY_TBL' (TABLE) (Cost=3 Card=2 Bytes=24)
4 3 INDEX (RANGE SCAN) OF 'HX_MY_TBL_IDX' (INDEX) (Cost=1 Card=2)
5 1 HASH JOIN (Cost=5 Card=1 Bytes=46)
6 5 VIEW (Cost=2 Card=2 Bytes=46)
7 6 TABLE ACCESS (FULL) OF 'SYS_TEMP_0FD9D6967_3C610F9' (TABLE (TEMP)) (Cost=2 Card=2 Bytes=24)
8 5 VIEW (Cost=2 Card=2 Bytes=46)
9 8 TABLE ACCESS (FULL) OF 'SYS_TEMP_0FD9D6967_3C610F9' (TABLE (TEMP)) (Cost=2 Card=2 Bytes=24)
here you can see the table is accessed only once then only the result set generated by the WITH is accessed.
Thanks,
Karthick.