将原始大小写混合的字符串存储在纯文本列中.使用没有长度修饰符的数据类型 text 或 varchar 而不是 varchar(n).它们本质上是相同的，但是使用 varchar(n) 您必须设置任意长度限制，如果您以后想更改，这可能会很痛苦.在在手册或在这个Peter Eisentraut @serverfault.SE 的相关回答.

Store the original mixed-case string in a plain text column. Use the data type text or varchar without length modifier rather than varchar(n). They are essentially the same, but with varchar(n) you have to set an arbitrary length limit, that can be a pain if you want to change later. Read more about that in the manual or in this related answer by Peter Eisentraut @serverfault.SE.

创建功能唯一索引 在 lower(string) 上.这是这里的主要观点:

Create a functional unique index on lower(string). That's the major point here:

CREATE UNIQUE INDEX my_idx ON mytbl(lower(name));

如果您尝试INSERT一个已经存在的小写混合大小写名称，则会出现唯一键违规错误.
对于快速相等搜索，请使用如下查询:

If you try to INSERT a mixed case name that's already there in lower case you get a unique key violation error.
For fast equality searches use a query like this:

SELECT * FROM mytbl WHERE lower(name) = 'foo' --'foo' is lower case, of course.

使用与索引中相同的表达式(以便查询规划器识别兼容性)，这将非常快.

Use the same expression you have in the index (so the query planner recognizes the compatibility) and this will be very fast.

顺便说一句:您可能想要升级到更新版本的 PostgreSQL.自 8.4.2 以来，有很多重要修复.有关官方 Postgres 版本控制站点的更多信息.

As an aside: you may want to upgrade to a more recent version of PostgreSQL. There have been lots of important fixes since 8.4.2. More on the official Postgres versioning site.