协助 Oracle 中的连接优化

Question

总的来说，我对 SQL 和编程还很陌生，我需要有关以下查询的帮助。它执行了几个小时，最终超时/连接关闭。

我已经尝试为连接中涉及的所有表创建复合索引，但它似乎根本没有帮助，这很奇怪。

这个查询过去运行得很好，但是在我向 Lods_F_D_O_Dlvr_Dtil 表的联接添加条件后开始出现挂起（这是注释行）。你建议我做些什么来提高性能？谢谢 :c)

Select 
        A1.Dcmt_Nmbr, 
        A3.Blng_Nmbr, 
        T5.Shpm_Nmbr, 
        T6.Splr_Code, 
        T6.Splr_Name, 
        A6.Cnpj_Cpf_Nmbr, 
        a7.cnpj_cpf_nmbr, 
        A5.ordr_rson_code
From Lods_F_D_F_Nota_Fisc A1
  Inner Join Lods_F_D_F_Nota_Fisc_Item A2 On A1.Dcmt_Nmbr = A2.Dcmt_Nmbr
  Inner Join Lods_F_D_F_Blng_Item A3      On A3.Blng_Nmbr = A2.Srce_Dcmt_Code
                                          And A3.Item_Nmbr = A2.Item_Nmbr 
  Inner Join Lods_F_D_S_Sles_Ordr_Item A4 On A4.Sles_Dcmt_Nmbr = A3.Sles_Dcmt_Nmbr
                                          And A4.Item_Nmbr = A3.Item_Dcmt_Sles
  Inner Join Lods_F_D_s_Sles_Ordr A5      on a5.sles_dcmt_nmbr = a4.sles_dcmt_nmbr
  inner Join Lods_F_D_O_Dlvr_Dtil T3      On T3.Sles_Dcmt_Nmbr=A4.Sles_Dcmt_Nmbr
                                          And T3.Item_Nmbr = A4.Item_Nmbr
                                          --AND T3.DLVR_NMBR=A3.DLVR_NMBR
  inner Join Lods_F_D_O_Dlvr T4           On T4.Dlvr_Nmbr=T3.Dlvr_Nmbr
  inner Join Lods_F_D_O_Shpm T5           On T5.Shpm_Nmbr=T4.Shpm_Nmbr
  Inner Join Lods_M_Plnt A6               On A6.Plnt_Code = A4.Plnt_Code
                                          And A6.End_Date is null
  Inner Join Lods_M_Cstm A7               On A7.Cstm_Code = A5.Cstm_Code
                                          and a7.end_date is null
  LEFT JOIN LODS_M_SPLR T6                ON T5.SPLR_CODE=T6.SPLR_CODE
                                          And T6.End_Date Is Null
group by 
        A1.Dcmt_Nmbr,
        A3.Blng_Nmbr,
        T5.Shpm_Nmbr,
        T6.Splr_Code,
        T6.Splr_Name,
        A6.Cnpj_Cpf_Nmbr,
        a7.cnpj_cpf_nmbr,
        A5.ordr_rson_code

这是执行计划：

https://i.stack.imgur.com/1KW9h.png

Answer 1

我在工作时看不到 EXPLAIN PLAN 并且图像被阻止。但是，我对正在发生的事情有一点想法。

您有问题的 JOIN 引用了多个表：T3、A3、A4。

  inner Join Lods_F_D_O_Dlvr_Dtil T3  On T3.Sles_Dcmt_Nmbr=A4.Sles_Dcmt_Nmbr
                                      And T3.Item_Nmbr = A4.Item_Nmbr
                                      AND T3.DLVR_NMBR=A3.DLVR_NMBR

这是允许的，但在大桌子和/或像你一样有很多关节的情况下，这是一个性能杀手。 Oracle 的优化器讨厌这种东西，因为它无法真正确定要使用的正确路径和索引，因此最终会进行全表扫描。

乍一看，我建议在 WHERE 子句中移动 T3/A3 比较，以便在所有关节发生后执行。这会将查询变成不同的东西，可能会或可能不会返回预期的结果，但试一试：

Select 
        A1.Dcmt_Nmbr, 
        A3.Blng_Nmbr, 
        T5.Shpm_Nmbr, 
        T6.Splr_Code, 
        T6.Splr_Name, 
        A6.Cnpj_Cpf_Nmbr, 
        a7.cnpj_cpf_nmbr, 
        A5.ordr_rson_code
From Lods_F_D_F_Nota_Fisc A1
  Inner Join Lods_F_D_F_Nota_Fisc_Item A2 On A1.Dcmt_Nmbr = A2.Dcmt_Nmbr
  Inner Join Lods_F_D_F_Blng_Item A3      On A3.Blng_Nmbr = A2.Srce_Dcmt_Code
                                          And A3.Item_Nmbr = A2.Item_Nmbr 
  Inner Join Lods_F_D_S_Sles_Ordr_Item A4 On A4.Sles_Dcmt_Nmbr = A3.Sles_Dcmt_Nmbr
                                          And A4.Item_Nmbr = A3.Item_Dcmt_Sles
  Inner Join Lods_F_D_s_Sles_Ordr A5      on a5.sles_dcmt_nmbr = a4.sles_dcmt_nmbr
  inner Join Lods_F_D_O_Dlvr_Dtil T3      On T3.Sles_Dcmt_Nmbr=A4.Sles_Dcmt_Nmbr
                                          And T3.Item_Nmbr = A4.Item_Nmbr
  inner Join Lods_F_D_O_Dlvr T4           On T4.Dlvr_Nmbr=T3.Dlvr_Nmbr
  inner Join Lods_F_D_O_Shpm T5           On T5.Shpm_Nmbr=T4.Shpm_Nmbr
  Inner Join Lods_M_Plnt A6               On A6.Plnt_Code = A4.Plnt_Code
                                          And A6.End_Date is null
  Inner Join Lods_M_Cstm A7               On A7.Cstm_Code = A5.Cstm_Code
                                          and a7.end_date is null
  LEFT JOIN LODS_M_SPLR T6                ON T5.SPLR_CODE=T6.SPLR_CODE
                                          And T6.End_Date Is Null

WHERE T3.DLVR_NMBR=A3.DLVR_NMBR
group by 
        A1.Dcmt_Nmbr,
        A3.Blng_Nmbr,
        T5.Shpm_Nmbr,
        T6.Splr_Code,
        T6.Splr_Name,
        A6.Cnpj_Cpf_Nmbr,
        a7.cnpj_cpf_nmbr,
        A5.ordr_rson_code