Re: Bug #730: cannot create functional index

On Sun, 4 Aug 2002 pgsql-bugs@postgresql.org wrote:

> Vadim Grepan (kezal@mail.ru) reports a bug with a severity of 3
> The lower the number the more severe it is.
>
> Short Description
> cannot create functional index
>
> Long Description
> I've tried to create functional index like
> that:
> === cut ===
> db=> CREATE INDEX NDX_FNC_TBL_TRAFBYTES__DATE ON tbl_trafbytes (date (date_trunc ('day', trafbytes_date)));
> ERROR:  parser: parse error at or near "("
> === cut ===
>
> Column trafbytes_date define as
> === cut ===
>  trafbytes_date    | timestamp without time zone | not null
> === cut ===
>
> Does it means that PostgreSQL funcional indexes support only simplest fucntions like lower ()?

Functional indexes must take as arguments one or more columns.
You'll need a function that wraps what you're attempting to do
and make the index (and where clauses) with that.