Re: Functional index definition

On Tue, 11 Nov 2003, [ISO-8859-1] Josué Maldonado wrote:

> Hello list,
>
> Is there a way to create indexes using functions like these:
> substring(prod_no,8,4)
> to_char(fkardex,'YYYYMM')
> substr(facnum,1,2)
>
> Help says is not possible but I would like to know if someone know an
> undocumented/tricky way to get that done.

Not directly in 7.3 and earlier.  You have to make a function that wraps
the function you want to call with static arguments like:

create function substring_8_4(text) returns text as
 'select substring($1, 8, 4);' language 'sql' immutable;

In 7.4, the indexes have been approved to allow indexes on expressions
which allow the above (with an extra set of parens in the definition).