用于UUID的最佳（最有效）DataType作为JPA ID [英] Best (most efficient) DataType to use for UUIDs as JPA IDs
问题描述
我想将UUID用作我的JPA对象的ID。
I want to use UUIDs as IDs for my JPA Objects.
我目前只使用String来存储UUID。什么会更有效？
I am currently just using a String to store the UUID. What would be more efficient?
推荐答案
你如何衡量效率？
例如，将UUID（这是 byte [] 的文本编码）存储为几个 long 值将允许您在64位体系结构上快速比较它们（比 String 比较，这是逐个字符的快得多）。但是，您的编码效率会受到影响，因为您必须编写自定义类型。
For example, storing the UUID (which is a text encoding of a byte[]) as a couple of long values will allow you to compare them very quickly on a 64-bit architecture (much more quickly than String comparison, which is character-by-character). However, your coding efficiency would suffer, because you have to write a custom type.
在您的情况下重要的是什么？
What is important in your case?
如果您对数据库中的性能感兴趣，性能将在一定程度上取决于您选择的数据库，但所有这些都将逐字节地比较UUID。因此，重要的是使键之间的差异更可能朝向键的开头。
If you are interested in performance within the database, performance will depend somewhat on the database you choose, but all will essentially compare UUIDs byte-by-byte. So, the important thing is to make differences between keys more likely to be toward the beginning of the key.
UUID在这方面设计得很好。最好的UUID是随机风格。它们在任何地方都没有很多共同的子串，包括开头，并且它们不会泄漏有关生成它们的机器的信息。但是，UUID的时间戳风格也是一个很好的关键，因为低位（快速变化）首先在字符串中，而高位（对于连续的UUID不会改变）来之后。
UUIDs are well-designed in this respect. The best UUID is the "random" style. They don't have a lot of common substrings anywhere, including the beginning, and they don't leak information about the machine that generated them. But, the "timestamp" style of UUIDs makes a good key as well, since the low-order bits (that vary quickly) are first in the string, while the high-order bits (that don't change for successive UUIDs) come later.
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