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独特的关键约束

[英]Unique Key Constraint

原文 2010-12-20 19:37:07 0 4 java/ design-patterns/ database-design/ application-design

What's the best practice in handling data insertion/update on a table with unique key constraints at the application level ? 在应用程序级别处理具有唯一键约束的表上的数据插入/更新的最佳实践是什么？ These are what I came up with: 这些是我想出的：

1. Run a query on the table before inserting data to see if it will violate the constraint. 1.在插入数据之前，在表上运行查询以查看它是否会违反约束。

Pros 优点

You have full control so you don't have to deal with any DBMS specific error messages. 您拥有完全的控制权，因此您不必处理任何特定于DBMS的错误消息。
Addtional layer of data integrity check 附加层的数据完整性检查

Cons 缺点

There might be a performance hit since there will be no constraint violation most of the time. 由于大多数情况下不会违反约束，因此可能会影响性能。
You will need to lock the table while you run the query for duplicate data. 在运行重复数据查询时，您将需要锁定表。

2. Do nothing. 2.什么都不做。 Update the table and see what sticks. 更新表，看看有什么问题。

Pros 优点

Simple! 简单！
Faster overall since you don't have to run an additional query everytime you update a table. 整体速度更快，因为您不必在每次更新表时都运行其他查询。

Cons 缺点

Your validation routine depends on the database layer. 您的验证例程取决于数据库层。
If the data doesn't stick, you have to wade through the stack trace to find the cause. 如果数据没有保留，则必须遍历堆栈跟踪以查找原因。

Which one is the more widely accepted solution? 哪个是更广泛接受的解决方案？ Are there alternatives to these? 有其他替代方法吗？

I'm using Java, JPA, Hibernate, and Spring BTW. 我正在使用Java，JPA，Hibernate和Spring BTW。 Any suggestions, even framework specific, are welcome! 欢迎任何建议，甚至是特定于框架的建议！

Thanks! 谢谢！

4 个解决方案

You've already pretty much sum it up. 您已经对它进行了总结。 If performance is a concern, go for 2nd way. 如果需要考虑性能，请选择第二种方法。 If integrity is a concern, go for 1st way. 如果要考虑完整性，请采用第一种方法。

I personally favor integrity over performance. 我个人更喜欢诚信而不是表现。 Hardware is pretty cheap, integrity not. 硬件很便宜，完整性不是。

Related questions: 相关问题：

Java - MySQL integrity violation handling Java-MySQL完整性违规处理

A third option is to use a MERGE operation (sometimes called UPSERT) if your DBMS supports it. 第三种选择是，如果您的DBMS支持，则使用MERGE操作（有时称为UPSERT）。 There is usually a DBMS specific way of checking whether the row was inserted or not. 通常，有一种DBMS特定的方式来检查是否插入了行。

Avoid the tautology "unique" key. 避免使用重言式“唯一”键。 Keys ARE unique, so the word "key" is quite sufficient to say what you mean. 键是唯一的，因此“键”一词足以说明您的意思。

I like the "optimistic" approach ("do nothing"). 我喜欢“乐观”的方法（“什么都不做”）。 You already enumerated the pros. 您已经列举了优点。 You are right that in this case you delegate validation to the DB layer. 没错，在这种情况下，您将验证委派给数据库层。 But inf you are using JPA the DB layer is also generated by java layer, so actually your validation depends on your annotation in java code. 但是，如果您使用的是JPA，则DB层也是由Java层生成的，因此实际上您的验证取决于Java代码中的注释。 Therefore it is not a big crime. 因此，这不是大罪。

A unique key is usually a business requirement, so you should use the business layer to check whether the one you intend to use is available. 唯一密钥通常是一项业务需求，因此您应使用业务层来检查您打算使用的密钥是否可用。 Delegating the checking to the database is an optimization, that should only be done when needed. 将检查委托给数据库是一种优化，只能在需要时执行。