Oracle - 使用 DBMS_MVIEW.REFRESH 刷新“REFRESH FORCE ON DEMAND”视图时会发生什么
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Oracle - What happens when refreshing a 'REFRESH FORCE ON DEMAND' view with DBMS_MVIEW.REFRESH
提问by contactmatt
I have the following materialized view -
我有以下物化视图 -
CREATE MATERIALIZED VIEW TESTRESULT
ON PREBUILT TABLE WITH REDUCED PRECISION
REFRESH FORCE ON DEMAND
WITH PRIMARY KEY
AS
SELECT...
FROM...
WHERE...
This materialized view has no backing MATERIALIZED VIEW LOG. As seen in the clause above this MV has "ON DEMAND" specifies, and according to Oracle documentation,
这个实体化视图没有支持实体化视图日志。如上面的条款所示，该 MV 具有“ON DEMAND”指定，并且根据 Oracle 文档，
"[ON DEMAND] indicate[s] that the materialized view will be refreshed on demand by calling one of the three DBMS_MVIEW refresh procedures."
“[ON DEMAND] 指示[s] 将通过调用三个 DBMS_MVIEW 刷新过程之一按需刷新物化视图。”
When I call DBMS_MVIEW.REFRESH('TESTRESULT') , what is occuring? Is it manually checking each record to see if it has been updated?
当我调用 DBMS_MVIEW.REFRESH('TESTRESULT') 时，发生了什么？是否手动检查每条记录以查看是否已更新？
Oracle Version: 10g
甲骨文版本：10g
回答by Justin Cave
By default (and this default changes in different versions of Oracle), that will do a full, atomic refresh on the materialized view. That means that the data in the materialized view will be deleted, the underlying query will be re-executed, and the results will be loaded into the materialized view. You can make the refresh more efficient by passing in a value of FALSE for the ATOMIC_REFRESHparameter, i.e.
默认情况下（在不同版本的 Oracle 中此默认更改），这将对物化视图进行完整的原子刷新。这意味着将删除物化视图中的数据，重新执行底层查询，并将结果加载到物化视图中。您可以通过为ATOMIC_REFRESH参数传入 FALSE 值来提高刷新效率，即
dbms_mview.refresh( 'TESTRESULT', atomic_refresh => false );
That will cause the materialized view to be truncated, the query re-executed, and the results inserted into the materialized view via a direct path insert. That will be more efficient than an atomic refresh but the materialized view will be empty during the refresh.
这将导致实体化视图被截断，查询重新执行，结果通过直接路径插入插入到实体化视图中。这将比原子刷新更有效，但物化视图在刷新期间将为空。
