sql - コミット時の具体化されたビューの更新

Question

TABLEと の2 つの列COL_1を持つテーブルがあるとしますCOL_2。

を読み取るだけの具体化されたビューがあり、次のようTABLE.COL_1に設定されていますREFRESH FAST ON COMMIT。

を更新するTABLE.COL_2と、マテリアライズド ビューは更新されますか?

Answer 1

はい、COL_2 を更新するとビューも更新されるようです。

COL_2 の更新は、マテリアライズド ビューのない同様のテーブルでの同等の更新よりも多くのリソースを使用します。また、COL_2 を更新すると、マテリアライズド ビューの行のタイムスタンプ (ORA_ROWSCN) が更新されます。

-------
--Compare the amount of work done to update.
--The difference isn't huge, but is significant and consistent.
-------

--Create table and materialized view
create table table1 (col_1 number primary key, col_2 number);
create materialized view log on table1;
create materialized view table1_mv refresh fast on commit
  as select col_1 from table1;
insert into table1 values(1, 1);
commit;

--Create a regular table for comparison
create table table2 (col_1 number primary key, col_2 number);
insert into table2 values(1, 1);
commit;

--Parse the queries so traces won't count that work.
update table1 set col_1 = 2;
update table1 set col_2 = 2;
update table2 set col_1 = 2;
update table2 set col_2 = 2;
rollback;

set autotrace on
alter system flush buffer_cache;
update table1 set col_1 = 2;
--         11  db block gets
--          8  consistent gets
--         13  physical reads

rollback;
alter system flush buffer_cache;
update table1 set col_2 = 2;
--          6  db block gets
--          8  consistent gets
--         12  physical reads

rollback;
alter system flush buffer_cache;    
update table2 set col_1 = 2;
--          7  db block gets
--          7  consistent gets
--          9  physical reads

rollback;
alter system flush buffer_cache;
update table2 set col_2 = 2;
--          3  db block gets
--          7  consistent gets
--          8  physical reads

set autotrace off


-------
--Compare ORA_ROWSCN.
--The times are different, implying the materialized view was modified.
-------

--(You may need to run these steps slowly to reproduce.  ORA_ROWSCN is
--not perfect, sometimes you'll see the same timestamp.)
select scn_to_timestamp(ora_rowscn) from table1_mv;
    --3/5/2011 12:25:25.000000000 AM
update table1 set col_1 = 3;
commit;
select scn_to_timestamp(ora_rowscn) from table1_mv;
    --3/5/2011 12:25:37.000000000 AM
update table1 set col_2 = 3;
commit;
select scn_to_timestamp(ora_rowscn) from table1_mv;
    --3/5/2011 12:25:46.000000000 AM