ORACLE:Materialiseret visning virker ikke, når du bruger LEFT JOIN

Der er to betingelser, der ikke er opfyldt for at få den materialiserede visning til at opdatere hurtigt. Den første er, at du ikke har angivet de rækkevidde kolonner for hver involveret tabel. Og den anden er en udokumenteret begrænsning:ANSI-joins er ikke understøttet.

Her er et eksempel, hvor DEPT er tabel_1, alias a og EMP er tabel_2, alias b:

SQL> create materialized view log on emp with rowid
  2  /

Materialized view log created.

SQL> create materialized view log on dept with rowid
  2  /

Materialized view log created.

SQL> create materialized view empdept_mv
  2    refresh fast on commit
  3  as
  4  select a.deptno
  5    from dept a
  6         left join emp b on (a.deptno = b.deptno)
  7  /
  from dept a
       *
ERROR at line 5:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view

Det efterligner din situation. Tilføj først rowidens:

SQL> create materialized view empdept_mv
  2    refresh fast on commit
  3  as
  4  select a.rowid dept_rowid
  5       , b.rowid emp_rowid
  6       , a.deptno
  7    from dept a
  8         left join emp b on (a.deptno = b.deptno)
  9  /
  from dept a
       *
ERROR at line 7:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view

Den kan stadig ikke hurtigt opdatere på grund af ANSI-tilslutningerne. Konvertering til gammeldags outer join-syntaks:

SQL> create materialized view empdept_mv
  2    refresh fast on commit
  3  as
  4  select a.rowid dept_rowid
  5       , b.rowid emp_rowid
  6       , a.deptno
  7    from dept a
  8       , emp b
  9   where a.deptno = b.deptno (+)
 10  /

Materialized view created.

Og for at bevise, at det virker:

SQL> select * from empdept_mv
  2  /

DEPT_ROWID         EMP_ROWID              DEPTNO
------------------ ------------------ ----------
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAA         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAB         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAC         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAD         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAE         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAF         30
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAG         10
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAH         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAI         10
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAJ         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAK         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAL         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAM         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAN         10
AAARhmAAEAAAAI/AAD                            40

15 rows selected.

SQL> insert into dept values (50,'IT','UTRECHT')
  2  /

1 row created.

SQL> commit
  2  /

Commit complete.

SQL> select * from empdept_mv
  2  /

DEPT_ROWID         EMP_ROWID              DEPTNO
------------------ ------------------ ----------
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAA         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAB         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAC         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAD         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAE         30
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAF         30
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAG         10
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAH         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAI         10
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAJ         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAK         20
AAARhmAAEAAAAI/AAC AAARhlAAEAAAAI3AAL         30
AAARhmAAEAAAAI/AAB AAARhlAAEAAAAI3AAM         20
AAARhmAAEAAAAI/AAA AAARhlAAEAAAAI3AAN         10
AAARhmAAEAAAAI/AAD                            40
AAARhmAAEAAAAI7AAA                            50

16 rows selected.

ANSI-join-syntaksbegrænsningen er nævnt i punkt 6 i dette blogindlæg .

Med venlig hilsen Rob.