基于 Oracle 函数的位图索引

Question

我正在使用 Oracle 11g，我有三个表，即 TABLE_1、TABLE_2、TABLE_3。在 select 语句中，我需要执行以下查询：

SELECT 
    -- // ommitted
FROM
    TABLE_1,
    TABLE_2,
    TABLE_3
WHERE
    -- // ommitted
    AND NVL(TABLE_1.COL_1, 0) = NVL(TABLE_2.COL, 0)
    AND (TABLE_1.COL_2 = TABLE_3.COL OR NVL(TABLE_1.COL_2, 0) = 0)

我想为以下内容创建基于函数的位图索引：

NVL(TABLE_1.COL_1, 0) = NVL(TABLE_2.COL, 0)
(TABLE_1.COL_2 = TABLE_3.COL OR NVL(TABLE_1.COL_2, 0) = 0)

可能吗？

对于NVL(TABLE_1.COL_1, 0) = NVL(TABLE_2.COL, 0) 我试过：

CREATE BITMAP INDEX TABLE_1_TABLE_2_NVL_COL_IDX 
ON     TABLE_1 (TABLE_2.COL) 
FROM   TABLE_1, TABLE_2
WHERE  NVL(TABLE_1.COL_1, 0) = NVL(TABLE_2.COL, 0);

但是它抛出了错误：

ORA-25954: missing primary key or unique constraint on dimension
25954. 00000 -  "missing primary key or unique constraint on dimension\n"
*Cause:    An attempt to create a join index was made, which failed
           because one or more dimensions did not have an appropriate
           constraint matching the join conditions.
*Action:   Ensure that the where clause is correct (contains all of the
           constraint columns) and that an enforced constraint is on
           each dimension table.

如果我能够创建索引，那么以下语法是否是在 select 语句中提供提示的正确方法？:

SELECT 
    /*+ INDEX (TABLE_1 TABLE_1_TABLE_2_NVL_COL_IDX) */
    /*+ INDEX (TABLE_1 TABLE_1_TABLE_3_NVL_COL_IDX) */
    -- // ommitted

Answer 1

位图连接索引受 number of restrictions 约束。即：

You cannot create a function-based join index.

The dimension table columns must be either primary key columns or have unique constraints.

第一个排除索引中有 nvl ( col, 0 )

第二个解释了您遇到的错误。您需要在 table_2.col 上添加主要或唯一约束。这也意味着此列中不应有空值！

因此您将需要一种不同的方法来为此查询编制索引。

基于 Oracle 函数的位图索引

Oracle Function based Bitmap Index

oracle

indexing

oracle11g

bitmap-index