January 2019
Beginner
556 pages
14h 19m
English
Content preview from Learning PostgreSQL 11 - Third Edition
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PostgreSQL function categories
When you are creating a function, it is marked as volatile by default if the volatility classification is not specified. If the created function is not volatile, it is important to mark it as stable or immutable, because this will help the optimizer to generate the optimal execution plans. PostgreSQL functions can fall into one of the following volatility classifications:
- Volatile: A volatile function can return different results for successive calls, even if the function argument didn't change; it can also change the data in the database. The random() function is a volatile function.
- Stable and immutable: These functions cannot modify the database, and they are guaranteed to return the same results for the ...
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