Re: Index on computed column

On Tue, 20 Apr 2004, Han Holl wrote:

> Hi,
>
> Can anyone explain to me what I'm doing wrong:
> (The first select is to show that the function rubriek exists, and does work).
> I want to create an index on a computed column:
>
> palga=> select rubriek(rapport, lseek, 'naamvrouw',0) from main
> where rapport = 'T098-20900';
> rubriek
> -----------
> Ramrattan
> (1 row)
> palga=> create index nm_idx on main (rubriek(rapport, lseek, 'naamvrouw',0));
> ERROR: parser: parse error at or near "'naamvrouw'" at character 54
> palga=>
>
> This is postgresql-7.3.4-3.rhl9.

In 7.3, functional indexes can only be across columns of the table, so
something like the above is illegal. You can get around this my making a
function that hardcodes the constants and then use that in the index and
queries.

In 7.4, you can index a more general set of expressions.