Question

我遇到了一些我不了解物化视图刷新时间的事情，并希望有人可以解释我所缺少的内容。我在12cR1上。

当我定义具有N秒刷新间隔的物化视图时，视图会编译并且基础作业会尽职地记录间隔并且看起来具有正确的NEXT_SEC，但视图不会继续-schedule具有定义的刷新间隔。

以下是一个例子。在这个例子中，我定义了一个每20秒刷新一次的轻量级mview。但是在监视其刷新时，通常需要30秒以上才能更新。如果Oracle不支持某些时间间隔，我希望mview编译失败，或者至少工作会被破坏，而不是悄悄地错过它的目标。

了解导致此结果的基础mview刷新机制的任何帮助都会很棒。任何关于更好地保持按计划的替代定义的建议也将受到赞赏。

由于

示例：

CREATE MATERIALIZED VIEW TIME_ONLY_MVIEW
REFRESH COMPLETE NEXT (SYSTIMESTAMP + NUMTODSINTERVAL(20, 'SECOND'))
AS
  SELECT SYSTIMESTAMP AS TIME_OF_MVIEW_QUERY
  FROM DUAL;

运行以下检查，我经常得到TIME_DELTA_SECONDS大于30.我想知道为什么。

WITH QUERY_TIME AS
(SELECT SYSTIMESTAMP AS TIME_OF_THIS_QUERY
 FROM DUAL)
SELECT
  TO_CHAR(QUERY_TIME.TIME_OF_THIS_QUERY, 'HH24:MI:SS')                                          TIME_OF_THIS_QUERY,
  TO_CHAR(TIME_ONLY_MVIEW.TIME_OF_MVIEW_QUERY, 'HH24:MI:SS')                                    TIME_OF_MVIEW_QUERY,
  LAST_RECORDED_REFRESH.LAST_RECORDED_REFRESH_START,
  LAST_RECORDED_REFRESH.LAST_RECORDED_REFRESH_END_TIME,
  EXTRACT(SECOND FROM (QUERY_TIME.TIME_OF_THIS_QUERY - TIME_ONLY_MVIEW.TIME_OF_MVIEW_QUERY)) AS TIME_DELTA_SECONDS,
  MVIEW_JOB.BROKEN,
  MVIEW_JOB.FAILURES,
  MVIEW_JOB.NEXT_SEC,
  MVIEW_JOB.MVIEW_INTERVAL
FROM QUERY_TIME
  CROSS JOIN TIME_ONLY_MVIEW
  CROSS JOIN (SELECT
                TO_CHAR(LAST_REFRESH_END_TIME, 'HH24:MI:SS') LAST_RECORDED_REFRESH_END_TIME,
                TO_CHAR(LAST_REFRESH_DATE, 'HH24:MI:SS')     LAST_RECORDED_REFRESH_START
              FROM USER_MVIEWS
              WHERE MVIEW_NAME = 'TIME_ONLY_MVIEW') LAST_RECORDED_REFRESH
  CROSS JOIN (SELECT
                USER_JOBS.BROKEN   BROKEN,
                USER_JOBS.FAILURES FAILURES,
                USER_JOBS.NEXT_SEC NEXT_SEC,
                USER_JOBS.INTERVAL MVIEW_INTERVAL
              FROM USER_JOBS
              WHERE USER_JOBS.WHAT LIKE 'dbms_refresh.refresh(%TIME_ONLY_MVIEW%);') MVIEW_JOB;

这是一个示例检查。工作永远不会中断，失败不会增加，但TIME_DELTA_SECONDS会增加到大约30秒，偶尔会达到40 +。

SQL> WITH QUERY_TIME AS
  2  (SELECT SYSTIMESTAMP AS TIME_OF_THIS_QUERY
  3   FROM DUAL)
  4  SELECT
  5    TO_CHAR(QUERY_TIME.TIME_OF_THIS_QUERY, 'HH24:MI:SS')                                          TIME_OF_THIS_QUERY,
  6    TO_CHAR(TIME_ONLY_MVIEW.TIME_OF_MVIEW_QUERY, 'HH24:MI:SS')                                    TIME_OF_MVIEW_QUERY,
  7    LAST_RECORDED_REFRESH.LAST_RECORDED_REFRESH_START,
  8    LAST_RECORDED_REFRESH.LAST_RECORDED_REFRESH_END_TIME,
  9    EXTRACT(SECOND FROM (QUERY_TIME.TIME_OF_THIS_QUERY - TIME_ONLY_MVIEW.TIME_OF_MVIEW_QUERY)) AS TIME_DELTA_SECONDS,
 10    MVIEW_JOB.BROKEN,
 11    MVIEW_JOB.FAILURES,
 12    MVIEW_JOB.NEXT_SEC,
 13    MVIEW_JOB.MVIEW_INTERVAL
 14  FROM QUERY_TIME
 15    CROSS JOIN TIME_ONLY_MVIEW
 16    CROSS JOIN (SELECT
 17                  TO_CHAR(LAST_REFRESH_END_TIME, 'HH24:MI:SS') LAST_RECORDED_REFRESH_END_TIME,
 18                  TO_CHAR(LAST_REFRESH_DATE, 'HH24:MI:SS')     LAST_RECORDED_REFRESH_START
 19                FROM USER_MVIEWS
 20                WHERE MVIEW_NAME = 'TIME_ONLY_MVIEW') LAST_RECORDED_REFRESH
 21    CROSS JOIN (SELECT
 22                  USER_JOBS.BROKEN   BROKEN,
 23                  USER_JOBS.FAILURES FAILURES,
 24                  USER_JOBS.NEXT_SEC NEXT_SEC,
 25                  USER_JOBS.INTERVAL MVIEW_INTERVAL
 26                FROM USER_JOBS
 27*               WHERE USER_JOBS.WHAT LIKE 'dbms_refresh.refresh(%TIME_ONLY_MVIEW%);') MVIEW_JOB;
TIME_OF_THIS_QUERY  TIME_OF_MVIEW_QUERY  LAST_RECORDED_REFRESH_START  LAST_RECORDED_REFRESH_END_TIME  TIME_DELTA_SECONDS  BROKEN  FAILURES  NEXT_SEC  MVIEW_INTERVAL                                   
12:09:14            12:08:44             12:08:44                     12:08:44                        30.197422           N       0         12:09:04  (SYSTIMESTAMP + NUMTODSINTERVAL(20, 'SECOND'))

物化视图刷新间隔粒度

0 个答案: