Dependencies of Function-Based Indexes (202)

Function-based indexes depend on the function used in the expression that defines the
index. If the function is a PL/SQL function or package function, the index is disabled
by any changes to the function specification.

To create a function-based index, the user must be granted CREATE INDEX or CREATE
ANY INDEX.

To use a function-based index:
■ The table must be analyzed after the index is created.
■ The query must be guaranteed not to need any NULL values from the indexed
expression, because NULL values are not stored in indexes.

函式索引的依賴性
1. 如果函式索引中的表示式為 PL/SQL 函式或包函式，當函式宣告發生變化時，索引將失效。
2. 需要授予create （any） index許可權才能建立按函式索引
3. 使用函式索引 ， 表必須在索引建立後進行分析 ， 且表示式中沒有NULL值

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