Oracle是否有过滤索引概念？

Question

到SQLServer的相似，我可以做以下

create index TimeSeriesPeriodSs1 on TimeSeriesPeriod (validationStatus, completionStatus) 
where completionStatus= N'Complete' 
and validationStatus= N'Pending' 

Answer 1

您可以在Oracle中创建一个基于函数的索引，它利用NULL值不存储在B树索引的事实。喜欢的东西

CREATE INDEX TimeSeriesPeriodSs1 
    ON TimeSeriesPeriod( 
      (CASE WHEN completionStatus = 'Complete' AND validationStatus = 'Pending' 
       THEN validationStatus 
       ELSE NULL 
      END), 
      (CASE WHEN completionStatus = 'Complete' AND validationStatus = 'Pending' 
       THEN completionStatus 
       ELSE NULL 
      END) 
     ); 

Answer 2

您可能能够使用基于函数的索引对于这一点，但它不是为这个场景非常愉快：

create index TimeSeriesPeriodSs1 on TimeSeriesPeriod (
    case when validationStatus= N'Pending' and completionStatus= N'Complete' then validationStatus else null end, 
    case when validationStatus= N'Pending' and completionStatus= N'Complete' then completionStatus else null end); 

你不得不使查询的where子句完全匹配以使其使用索引。

select <fields> 
from TimeSeriesPeriod 
where case when validationStatus= N'Pending' and completionStatus= N'Complete' then validationStatus else null end = N'Pending' 
and case when validationStatus= N'Pending' and completionStatus= N'Complete' then completionStatus else null end = N'Complete'; 

这将是一个很大整洁，如果你可以定义（确定性）功能做case。有关更多信息和示例，请参阅here。或者从Google上快速获得this。

Answer 3

这里有贾斯汀和亚历克斯的回答一个小的变体可能进一步节省索引空间，使修改后的查询更具可读性IMO：

CREATE INDEX TimeSeriesPeriodSs1 
    ON TimeSeriesPeriod( 
      (CASE WHEN completionStatus = 'Complete' AND validationStatus = 'Pending' 
       THEN 1 
       ELSE NULL 
      END); 

SELECT * FROM TimeSeriesPeriod 
    WHERE 1 = (CASE WHEN completionStatus = 'Complete' AND validationStatus = 'Pending' 
       THEN 1 
       ELSE NULL 
      END)