Re: [SQL] Functional Indexes

On Mon, 8 Feb 1999, Sascha Schumann wrote:

> On Sat, Feb 06, 1999 at 12:27:47PM -0500, Tom Lane wrote:
> > "Bryan White" <bryan@arcamax.com> writes:
> > > The documentation for CREATE INDEX implies that functions are allowed in
> > > index definitions but when I execute:
> > > create unique index idxtest on customer (lower(email));
> > > the result is:
> > > ERROR:  DefineIndex: (null) class not found
> > > Should this work?  Do I have the syntax wrong?
> >
> > I tried this wih 6.4.2 and found that it was only accepted if I
> > explicitly identified which index operator class to use:
> >
> > play=> create table customer (email text);
> > CREATE
> > play=> create unique index idxtest on customer (lower(email));
> > ERROR:  DefineIndex:  class not found
> > play=> create unique index idxtest on customer (lower(email) text_ops);
> > CREATE
> > play=>
> >
> > That'll do as a workaround for Bryan, but isn't this a bug?  Surely
> > the system ought to know what type the result of lower() is...
> >
> >             regards, tom lane
>
> I still have a problem with that ... edited typescript follows
>
> funweb=> \d userdat
> Table    = userdat
> +----------------------------------+----------------------------------+-------+
> |              Field               |              Type                | Length|
> +----------------------------------+----------------------------------+-------+
> | username                         | varchar() not null               |    30 |
> ...
> +----------------------------------+----------------------------------+-------+
> Index:    userdat_pkey
> funweb=> create unique index userdat_idx2 on userdat (lower(username)
> varchar_ops);
> ERROR:  BuildFuncTupleDesc: function 'lower(varchar)' does not exist
>
> This error message looks very bogus to me.
>
> --
>
>           Regards,
>
>                             Sascha Schumann |
>                                  Consultant | finger sas@schell.de
>                                             | for PGP public key
>

I don't think lower is defined for varchar arguments.  consider redefining
username as type text and using text_ops.

This method worked on my system:

stocks=> create table temptext (a text, b varchar(20));
CREATE
stocks=> create index itemptext on temptext using btree(lower(a) text_ops) ;
CREATE

Your error reproduced:

stocks=> create index i2temptext on temptext using btree(lower(b) text_ops) ;
ERROR:  BuildFuncTupleDesc: function 'lower(varchar)' does not exist

Excerpt from function definitions( both return value and argument are text
types):

text     |lower              |text          |lowercase

Marc Zuckman
marc@fallon.classyad.com

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