使用物化视图跟踪最新版本的记录

Question

我们有一个高度（可能已经结束？）规范化的表，用于跟踪版本化的值。它只是插入，没有更新。

示例数据：

"ID"    "Version"   "Value"
1       0           "A_1"
2       0           "B_1"
1       1           "A_2"
3       0           "C_1"

我们经常运行查询以仅提取每个 ID 的最新值。当我们达到数百万行时，我们开始遇到性能问题。我已经能够使用物化视图对改进进行原型改进，但无法以它们自刷新“ON COMMIT”的方式创建它们

到目前为止我得到的是这个（以下修订）

CREATE MATERIALIZED VIEW TABLE_LATEST 
    BUILD IMMEDIATE
    REFRESH FAST 
    ON COMMIT AS

SELECT  T.ID
       ,T.LAST_VERSION
FROM (
    SELECT  ID
           ,MAX(VERSION) OVER (PARTITION BY ID) LAST_VERSION
    FROM    TABLE
) T
GROUP BY T.ID, T.LAST_VERSION;

现在根据反馈进行了修订：

CREATE MATERIALIZED VIEW TABLE_LATEST 
    BUILD IMMEDIATE
    REFRESH FAST 
    ON COMMIT AS

SELECT  ID
       ,MAX(VERSION)
FROM    TABLE
GROUP BY T.ID;

失败的原因是：

ORA-12033: 无法使用实体化视图登录中的筛选列 “模式”。“表”

*Cause:    The materialized view log either did not have filter columns
           logged, or the timestamp associated with the filter columns was
           more recent than the last refresh time.

*Action:   A complete refresh is required before the next fast refresh.
           Add filter columns to the materialized view log, if required.

如果我将Refresh 更改为Force 并删除On Commit，它只会“工作”。我不知道这是否属于物化视图的“无分析”规则，或者我是否一开始就错误地创建了日志？

CREATE MATERIALIZED VIEW LOG ON TABLE
LOGGING 
WITH SEQUENCE, ROWID, (VALUE) 
INCLUDING NEW VALUES;

表架构：

CREATE TABLE "TABLE"
(
  ID NUMBER(10, 0) NOT NULL 
, VERSION NUMBER(10, 0) NOT NULL 
, VALUE VARCHAR2(4000 CHAR) 
, CONSTRAINT MASTERRECORDFIELDVALUES_PK PRIMARY KEY 
  (
    ID
  , VERSION 
  )
  USING INDEX 
  (
      CREATE UNIQUE INDEX TABLE_PK ON TABLE(ID ASC, VERSION ASC) 
      LOGGING 
      ...
  )
  ENABLE 
) 
LOGGING 

我是否走在正确的轨道上？是否有更好的方法来预先计算最新版本？还是我只需要拨入 Log & View 设置？

Answer 1

很抱歉，我不能马上给你答复。一个原因可能是使用了 MV 不太支持的分析函数。要分析问题，您需要查看物化视图的功能。

DECLARE
  -- Local variables here
  --
  v_sql VARCHAR2(32000) := 'SELECT  T.ID
                                   ,T.LAST_VERSION
                            FROM (SELECT  ID
                                         ,MAX(VERSION) OVER (PARTITION BY ID) LAST_VERSION    
                                  FROM    TABLE) T
                                  GROUP BY T.ID
                                          ,T.LAST_VERSION';

   v_msg_arrray SYS.EXPLAINMVARRAYTYPE;
   msg SYS.ExplainMVMessage;
BEGIN
  -- Test statements here
   dbms_mview.explain_mview(mv => v_sql, msg_array => v_msg_arrray);



  FOR i IN v_msg_arrray.FIRST..v_msg_arrray.LAST LOOP
    msg := v_msg_arrray(i);
    DBMS_OUTPUT.put_line('MVOWNER:' || msg.MVOWNER);
    DBMS_OUTPUT.put_line('MVNAME:' || msg.MVNAME);
    DBMS_OUTPUT.put_line('CAPABILITY_NAME:' || msg.CAPABILITY_NAME);
    DBMS_OUTPUT.put_line('POSSIBLE:' || msg.POSSIBLE);
    DBMS_OUTPUT.put_line('RELATED_TEXT:' || msg.RELATED_TEXT);
    DBMS_OUTPUT.put_line('RELATED_NUM:' || msg.RELATED_NUM);
    DBMS_OUTPUT.put_line('MSGNO:' || msg.MSGNO);    
    DBMS_OUTPUT.put_line('MSGTXT:' || msg.MSGTXT);
    DBMS_OUTPUT.put_line('SEQ:' || msg.SEQ);
    DBMS_OUTPUT.put_line('----------------------------------------');
  END LOOP;

END;

顺便说一句：您可以更简单地编写查询：

SELECT t.id,
       MAX(t.version) AS last_version
FROM table t
GROUP BY t.id;

Answer 2

如果您不需要与最新版本关联的值，那么您可以简单地这样做：

CREATE MATERIALIZED VIEW LOG ON t1 
LOGGING  
WITH SEQUENCE, ROWID, (val) 
INCLUDING NEW VALUES;

create materialized view t1_latest
refresh fast on commit
as
  select id,
         max(version) latest_version
  from   t1
  group by id;

这个测试用例可以在over at Oracle LiveSQL找到。

---

否则，您需要创建三个单独的 MV（因为您无法在提交时快速刷新涉及将 dense_rank 保持在第一个/最后一个的物化视图） - 根据 http://www.sqlsnippets.com/en/topic-12926.html - 就像这样：

主表的物化视图日志：

CREATE MATERIALIZED VIEW LOG ON t1
LOGGING 
WITH SEQUENCE, ROWID, (val)
INCLUDING NEW VALUES;

第一个物化视图：

create materialized view t1_sub_mv1
refresh fast on commit
as
  select id,
         max(version) latest_version,
         count(version) cnt_version,
         count(*) cnt_all
  from   t1
  group by id;

第一个物化视图上的物化视图日志：

create materialized view log on t1_sub_mv1
with rowid, sequence (id, latest_version, cnt_version, cnt_all)
including new values;

第二个实体化​​视图：

create materialized view t1_sub_mv2
refresh fast on commit
as
  select id,
         version,
         max(val) max_val_per_id_version,
         count(*) cnt_all
  from   t1
  group by id,
           version;

第一个物化视图上的物化视图日志：

create materialized view log on t1_sub_mv2
with rowid, sequence (id, max_val_per_id_version, cnt_all)
including new values;

第三个也是最后一个物化视图：

create materialized view t1_main_mv
refresh fast on commit
as
  select mv1.id,
         mv1.latest_version,
         mv2.max_val_per_id_version val_of_latest_version,
         mv1.rowid mv1_rowid,
         mv2.rowid mv2_rowid
  from   t1_sub_mv1 mv1,
         t1_sub_mv2 mv2
  where  mv1.id = mv2.id
  and    mv1.latest_version = mv2.version;

对此的支持测试用例可以在over at Oracle LiveSQL找到。