如何改善我的Oracle查詢？

Question

我在Oracle中有一個查詢，單個查詢需要3秒鍾或更長時間，但就我而言，我多次執行該查詢來處理多個記錄，因此總體上需要更多時間。
為了提高查詢性能，我執行了以下操作。

我已經執行了SQL調優咨詢並創建了建議索引，但是建議索引在執行計划中不起作用，它顯示了與先前相同的主鍵索引，我將為此做些什么。

我的查詢是：

Select NVL(Min(MACIDREFNO),0)
from   TACID_MST
Where  MacIdStatus = 2
And    Status = 0 
And    UsedAs = 1
And    IsCodeSigned = 0
And    SiteRefNo = 0;

執行計划是：
執行計划

SQL調整咨詢的結果是：

GENERAL INFORMATION SECTION `Result of Tuning Advisory`
-------------------------------------------------------------------------------
Tuning Task Name                  : staName75534
Tuning Task Owner                 : TESTUSER
Tuning Task ID                    : 385915
Scope                             : COMPREHENSIVE
Time Limit(seconds)               : 1800
Completion Status                 : COMPLETED
Started at                        : 01/24/2018 15:46:15
Completed at                      : 01/24/2018 15:46:17
Number of Index Findings          : 1

-------------------------------------------------------------------------------
FINDINGS SECTION (1 finding)
-------------------------------------------------------------------------------

1- Index Finding (`see explain plans section below`)
--------------------------------------------------
  The execution plan of this statement can be improved by creating one or more
  indices.

  Recommendation (estimated benefit: 100%)
  ----------------------------------------
  - Consider running the Access Advisor to improve the physical schema design
    or creating the recommended index.

        create index TESTUSER.IDX$$_5E37B0001 on
        TESTUSER.TACID_MST('STATUS','USEDAS','MACIDSTATUS','SITEREFNO','ISCODESIGNED');

  Rationale
  ---------
    Creating the recommended indices significantly improves the execution plan
    of this statement. However, it might be preferable to run "Access Advisor"
    using a representative SQL workload as opposed to a single statement. This
    will allow to get comprehensive index recommendations which takes into
    account index maintenance overhead and additional space consumption.    

Answer 1

最簡單的方法：

• 重建索引sys_iot_top_147733（如果不是IOT），或者如果可能的話，移動（重建）IOT
• 使用綁定變量
• 收集表TACID_MST上的統計信息
• 更改新索引的列順序（首先將限制性最強的列值放在第一位（唯一值最高的列））
• 使用提示進行強制索引使用：從中選擇/ * + INDEX（TACID_MST your_index_name）* / NVL（Min（MACIDREFNO），0）