I have added the following patch to the FAQ to mention the use of
functional indexes for case-insensitive equality comparisons.
> Hi,
>
> I've trolled the archives and the FAQ and the closest I could come up with was
> the following mailing list message:
>
> http://www.postgresql.org/mhonarc/pgsql-general/2001-01/msg01632.html
>
> which advises that you can do something like this to create a case-insensitive
> unique index:
>
> CREATE UNIQUE INDEX indexname ON tablename (lower(fieldname))
>
> however, that doesn't work under 7.0.2 at least, I get:
>
> mydb=> create unique index forward_rr on forward (lower(name));
> ERROR: DefineIndex: function 'lower(varchar)' does not exist
>
> Futhermore, I want to create the case-insensitive unique index on a tuple of
> varchar fields, ie.:
>
> CREATE UNIQUE INDEX indexname ON tablename (lower(field1), lower(field2), lower(field3))
>
> however, looking at the docs at:
>
> http://www.postgresql.org/users-lounge/docs/7.0/user/sql-createindex.htm
>
> it looks like I will need to instead declare a function f such that it can be used as:
>
> CREATE UNIQUE INDEX indexname ON tablename (f(field1, field2, field3))
>
> and f(n1, n2, n3) returns a unique value for unique combinations of n1, n2 and
> n3...
>
> Since this sounds like something someone must have already done, or should be
> a FAQ, any hints? pointers? functions? PL/SQL code?
>
> Thanks,
> Adi
>
>
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