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DB2 中 MQT 的匹配原理及使用技巧

 2010-03-31 00:00:00 来源:WEB开发网   
核心提示: 下面是 fd.plan 打印出的执行计划和诊断信息:OptimizedStatement:---SELECTQ3.CAT_DESCAS"CAT_DESC",Q1.TOTALFROMMQTSCH.SALES_BY_CATASQ1,(SELECTDISTINCTQ2.CAT_DE

下面是 fd.plan 打印出的执行计划和诊断信息:

 Optimized Statement: 
 ------------------- 
 SELECT Q3.CAT_DESC AS "CAT_DESC", Q1.TOTAL 
 FROM MQTSCH.SALES_BY_CATAS Q1, 
 (SELECT DISTINCTQ2.CAT_DESC, Q2.CAT_ID 
 FROM MQTSCH.PRODUCT AS Q2) AS Q3 
 WHERE (Q1.CAT_ID = Q3.CAT_ID) 
 
 Access Plan: 
 ----------- 
    Total Cost:       98.6553 
    Query Degree:      1 
 
      Rows 
      RETURN 
      (  1) 
      Cost 
       I/O 
       | 
       0.4 
      HSJOIN 
      (  2) 
      98.6553 
       10 
     /---+----\ 
    10      1 
   TBSCAN    TBSCAN 
   (  3)    (  4) 
   74.9814   23.5881 
    9      1 
    |      | 
    10      1 
 TABLE: MQTSCH   SORT 
 SALES_BY_CAT  (  5) 
    Q1     23.5366 
           1 
          | 
          200 
         TBSCAN 
         (  6) 
         23.4286 
           1 
          | 
          200 
       TABLE: MQTSCH 
         PRODUCT 
          Q2 
 
 
 Extended Diagnostic Information: 
 -------------------------------- 
 
 Diagnostic Identifier: 1 
 Diagnostic Details: EXP0073W The following MQT or statistical view was 
 not eligible because one or more data filtering 
 predicates from the query could not be matched with 
 the MQT: "MQTSCH "."SALES_BY_CAT". 
 Diagnostic Identifier: 2 
 Diagnostic Details: EXP0148W The following MQT or statistical view was 
 considered in query matching: "MQTSCH ". 
 "SALES_BY_CAT". 
 Diagnostic Identifier: 3 
 Diagnostic Details: EXP0149W The following MQT was used (from those 
 considered) in query matching: "MQTSCH ". 
 "SALES_BY_CAT". 

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Tags:DB MQT 匹配

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