PostgreSQL中的Checksum字段与内容比较 [英] Checksum field in PostgreSQL to content comparison

问题描述

我在表中的一个字段包含大量内容（文本或二进制数据）。如果我想知道另一文本是否等于该文本，则可以使用校验和比较这两个文本。我可以将此字段定义为 UNIQUE 以避免重复的内容。

I have a field in a table with large content (text or binary data). If I want to know if another text is equals this one, I can use a checksum to compare the two texts. I can define this field as UNIQUE to avoid repeated content too.

我的疑问是是否创建校验和字段，此比较将加快速度，因此PostgreSQL已经执行了此操作（无需程序员干预）还是我需要手动执行此操作？

My doubt is if I create a checksum field, this comparison will speed up, so PostgreSQL already does this (without need programmer intervention) or I need do this manually?

编辑：更好，为 TEXT 字段创建一个校验和，对其使用校验和还是两种方式相同？

What is better, create a checksum for a TEXT field, use a checksum for it or the two ways are the same thing?

推荐答案

PostgreSQL中的大列没有默认的校验和，您必须自己实现一个。

There is no default "checksum" for large columns in PostgreSQL, you will have to implement one yourself.

哈希索引可为平等检查提供快速性能。并且它们会自动更新。但是它们尚未完全集成到PostgreSQL中，因此不鼓励使用-阅读手册。

Hash indexes provide fast performance for equality checks. And they are updated automatically. But they are not fully integrated in PostgreSQL (yet), so their use is discouraged - read the manual.

您将无法查询值并在应用程序中使用它们。您可以使用校验和列来做到这一点，但是如果表很大并需要维护该列，则需要添加性能索引。为此，我将使用触发器在插入或更新之前。

And you cannot query the values and use them in your application for instance. You could do that with a checksum column, but you need to add an index for performance if your table is big and maintain the column. I would use a trigger BEFORE INSERT OR UPDATE for that.

因此，哈希索引可能会也可能不会为了你。 @AH的想法肯定适合这个问题...

So, a hash index may or may not be for you. @A.H.'s idea certainly fits the problem ...

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