Group BY 查询利用索引，但 window 函数查询不

Question

我使用 IBM 的 COTS 系统，称为 Maximo Asset Management。系统有一个 WORKORDER table 有 350,000 行。

Maximo 有一个名为 relationships 的概念，可用于从相关记录中提取数据。

人际关系如何运作：

对于每个人 WORKORDER 记录，系统使用 WHERE 子句从关系到运行一个 select 查询来拉入相关记录（ screenshot).

相关记录：

在这种情况下，相关记录是名为 WOTASKROLLUP_VW.

的自定义数据库视图中的行

在相关的 post 中，我探索了可以在视图中使用的不同 SQL 汇总技术：Group by x, get other fields too。当我在完整的 WORKORDER table.

上运行时，我探索的选项彼此表现相似

然而，实际上，Maximo 被设计为一次只能获取一行——通过单独的 select 语句。因此，当仅 select 单个 WORKORDER 记录时，查询 表现非常不同 。

我已经将每个查询包装在一个外部查询中，其中包含一个 select 特定工作订单的 WHERE 子句。我这样做是为了模仿 Maximo 在使用关系时所做的事情。

查询 1b:（GROUP BY；select5 个聚合）

性能 非常好，即使只 selecting 一条记录，因为使用了索引（仅 37 毫秒）。

select
    *
from
    (
    select 
        wogroup as wonum, 
        sum(actlabcost)  as actlabcost_tasks_incl,
        sum(actmatcost)  as actmatcost_tasks_incl,
        sum(acttoolcost) as acttoolcost_tasks_incl,
        sum(actservcost) as actservcost_tasks_incl,
        sum(actlabcost + actmatcost + acttoolcost + actservcost) as acttotalcost_tasks_incl,
        max(case when istask = 0 then rowstamp end) as other_wo_columns
    from 
        maximo.workorder
    group by 
        wogroup
    )
where
    wonum in ('WO360996')
------------------------------------------------------------------------------------------------
| Id  | Operation                    | Name            | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |                 |     1 |    34 |     4   (0)| 00:00:01 |
|   1 |  SORT GROUP BY NOSORT        |                 |     1 |    34 |     4   (0)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| WORKORDER       |     1 |    34 |     4   (0)| 00:00:01 |
|*  3 |    INDEX RANGE SCAN          | WORKORDER_NDX32 |     1 |       |     3   (0)| 00:00:01 |
------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
   3 - access("WOGROUP"='WO360996')

查询 #2：（SUM window 函数）

性能相对慢，当select单个记录时，因为没有使用索引（3 秒）。

select
    *
from
    (
    select
        wonum,
        actlabcost_tasks_incl,
        actmatcost_tasks_incl,
        acttoolcost_tasks_incl,
        actservcost_tasks_incl,
        acttotalcost_tasks_incl,
        other_wo_columns
    from
        (
        select
            wonum,
            istask,
            sum(actlabcost ) over (partition by wogroup) as actlabcost_tasks_incl,
            sum(actmatcost ) over (partition by wogroup) as actmatcost_tasks_incl,
            sum(acttoolcost) over (partition by wogroup) as acttoolcost_tasks_incl,
            sum(actservcost) over (partition by wogroup) as actservcost_tasks_incl,
            sum(actlabcost + actmatcost + acttoolcost + actservcost) over (partition by wogroup) as acttotalcost_tasks_incl,
            rowstamp as other_wo_columns
        from
            maximo.workorder
        )
    where
        istask = 0
    )
where
    wonum in ('WO360996')
-----------------------------------------------------------------------------------------
| Id  | Operation           | Name      | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |           |   355K|    61M|       | 14789   (1)| 00:00:01 |
|*  1 |  VIEW               |           |   355K|    61M|       | 14789   (1)| 00:00:01 |
|   2 |   WINDOW SORT       |           |   355K|    14M|    21M| 14789   (1)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| WORKORDER |   355K|    14M|       | 10863   (2)| 00:00:01 |
-----------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
   1 - filter("WONUM"='WO360996' AND "ISTASK"=0)

问题：

为什么 #1B 中的 GROUP BY 查询能够使用索引（快），而 #2 中的 Sum Window 函数不能使用索引（慢）？

Answer 1

您的两个查询与您使用的第一个查询不同：

select wogroup as wonum,

而您刚刚使用的第二个：

select wonum,

这意味着您不会在 WOGROUP 上使用索引，因为您在 WONUM 列而不是 WOGROUP 列上进行过滤（恰好别名为WONUM).

看起来你的第二个查询可以更正和减少（通过将过滤器移动到内部子查询并删除分区，因为你已经在过滤）到：

select wonum,
       actlabcost_tasks_incl,
       actmatcost_tasks_incl,
       acttoolcost_tasks_incl,
       actservcost_tasks_incl,
       acttotalcost_tasks_incl,
       other_wo_columns
from   (
  select wogroup AS wonum,
         istask,
         sum(actlabcost ) over () as actlabcost_tasks_incl,
         sum(actmatcost ) over () as actmatcost_tasks_incl,
         sum(acttoolcost) over () as acttoolcost_tasks_incl,
         sum(actservcost) over () as actservcost_tasks_incl,
         sum(actlabcost + actmatcost + acttoolcost + actservcost) over () as acttotalcost_tasks_incl,
         rowstamp as other_wo_columns
  from   maximo.workorder
  where  wogroup = 'WO360996'
)
where istask = 0;

Group BY 查询利用索引，但 window 函数查询不

Group BY query utilizes indexes, but window function query doesn't

oracle

query-optimization

maximo

oracle19c