Database upgrade - slow query performance

Question

Hi,
recently we have upgraded our 8i database to an 10g database.
While we was testing our forms application against the new
10g database there was a very slow sql-statements which runs
several minutes but it runs against the 8i database within seconds.
With sqlplus it runs sometimes fast, sometimes slow (see execution plan below)
in 10g.
The sql-statement in detail:
SELECT name1, vornam, aboid, liefstat
FROM aktuellerabosatz
WHERE aboid = evitadba.get_evitaid ('0000002100')
"aktuellerabosatz" is a view on a table with about 3.000.000 records.
The function get_evitaid gets only the substring of the last 4 diggits of the whole
number.
execution plan with slow responce time:
12:05:31 EVITADBA-TSUN>SELECT name1, vornam, aboid, liefstat
12:05:35 2 FROM aktuellerabosatz
12:05:35 3 WHERE aboid = evitadba.get_evitaid ('0000002100');
NAME1 VORNAM ABOID L
RETHMANN ENTSORGUNGSWIRTSCHAFT 2100 A
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Ausführungsplan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=4 Card=1 Bytes=38)
1 0 TABLE ACCESS (BY INDEX ROWID) OF 'EVTABO' (TABLE) (Cost=4
Card=1 Bytes=38)
2 1 INDEX (RANGE SCAN) OF 'EVIABO22' (INDEX (UNIQUE)) (Cost=
3 Card=1)
Statistiken
100 recursive calls
0 db block gets
121353 consistent gets
121285 physical reads
0 redo size
613 bytes sent via SQL*Net to client
500 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
execution plan with fast response time:
12:06:43 EVITADBA-TSUN>SELECT name1, vornam, aboid, liefstat
12:06:58 2 FROM aktuellerabosatz
12:06:58 3 WHERE aboid = evitadba.get_evitaid ('0000002100');
NAME1 VORNAM ABOID L
RETHMANN ENTSORGUNGSWIRTSCHAFT 2100 A
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Ausführungsplan
0 SELECT STATEMENT Optimizer=CHOOSE (Cost=4 Card=1 Bytes=38)
1 0 TABLE ACCESS (BY INDEX ROWID) OF 'EVTABO' (TABLE) (Cost=4
Card=1 Bytes=38)
2 1 INDEX (RANGE SCAN) OF 'EVIABO22' (INDEX (UNIQUE)) (Cost=
3 Card=1)
Statistiken
110 recursive calls
8 db block gets
49 consistent gets
0 physical reads
0 redo size
613 bytes sent via SQL*Net to client
500 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
In the fast response the consistent gets and physical reads are very small
but in the another time very high what (it seems) results in the slow performance.
What could be the reasons?
kind regards
Marco

Answer 1

The two execution plans above are both 10g-sqlsessions on the same database with the same user. We gather statistics for the database with the dbms_stats package. Normally we have the all_rows option. The confusing thing is sometimes the sql-statement runs fas sometimes slow in a sqlplus session with the same executin plan only the physical gets, constent reads are extreme different.
If we rewrite the sql-statement to use the table evtabo with the an additional
where clause (which is from the view) instead of using the view then it runs fast:
14:24:04 H00ZRETH-TSUN>SELECT name1, vornam, aboid, liefstat
14:24:14 2 FROM aktuellerabosatz
14:24:14 3 WHERE aboid = evitadba.get_evitaid ('0000000246');
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Ausführungsplan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=27315 Card=1204986
Bytes=59044314)
1 0 VIEW OF 'EVTABO_V1' (VIEW) (Cost=27315 Card=1204986 Bytes=
59044314)
2 1 TABLE ACCESS (FULL) OF 'EVTABO' (TABLE) (Cost=27315 Card
=1204986 Bytes=45789468)
14:24:59 H00ZRETH-TSUN>SELECT name1, vornam, aboid, liefstat
14:25:26 2 FROM evtabo
14:25:26 3 WHERE aboid = evitadba.get_evitaid ('0000002100')
14:25:26 4 and gueltab <= TRUNC(sysdate) AND (gueltbs >=TRUNC(SYSDATE) OR gueltbs IS NULL);
NAME1 VORNAM ABOID L
RETHMANN ENTSORGUNGSWIRTSCHAFT 2100 A
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Ausführungsplan
0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=4 Card=1 Bytes=38)
1 0 TABLE ACCESS (BY INDEX ROWID) OF 'EVTABO' (TABLE) (Cost=4
Card=1 Bytes=38)
2 1 INDEX (RANGE SCAN) OF 'EVIABO22' (INDEX (UNIQUE)) (Cost=
3 Card=1)
What could be the reason for the different performance in 8i and 10g?
Thanks
Marco