Re: Get index information from information_schema?

> -----Original Message-----
> From: Erik Jones [mailto:erik@myemma.com]
> Sent: Tuesday, March 18, 2008 11:51 AM
> To: Dann Corbit
> Cc: Albe Laurenz; AlannY *EXTERN*; pgsql-general@postgresql.org
> Subject: Re: [GENERAL] Get index information from information_schema?
>
>
> On Mar 18, 2008, at 1:28 PM, Dann Corbit wrote:
>
> >> -----Original Message-----
> >> From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-
> >> owner@postgresql.org] On Behalf Of Albe Laurenz
> >> Sent: Tuesday, March 18, 2008 1:24 AM
> >> To: AlannY *EXTERN*; pgsql-general@postgresql.org
> >> Subject: Re: [GENERAL] Get index information from
information_schema?
> >>
> >> AlannY wrote:
> >>> I need a method of extracting information about indexes of any
table
> >>> from information_schema.
> >>>
> >>> Have you any suggestions?
> >>
> >> I am afraid that indexes are not covered by information_schema.
> >>
> >> You'd have to dig into pg_catalog.pg_index for this.
> >
> > Doesn't the PostgreSQL schema have the
> > INFORMATION_SCHEMA.KEY_COLUMN_USAGE view?
> >
> > Or (conversely) are indexes not stored as constraints?
>
> Only if they are PRIMARY KEY or UNIQUE indexes.

It looks like Foreign keys are included as well, because I get the
correct results for this query:

create table t1 (c1 int not null, c2 int not null, c3 char(5), c4 int,
c5 int, constraint pk_t1 PRIMARY KEY (c5,c4));

create table t2 (tc1 int not null, c1 int not null, c2 int not null, c5
char(5), constraint fk_t2 FOREIGN KEY (c1,c2) references t1 (c5,c4));

select CONSTRAINT_NAME, TABLE_NAME, COLUMN_NAME, ORDINAL_POSITION from
information_schema.key_column_usage where TABLE_NAME in ('t1', 't2');

So the only thing that will be missing are the indexes that are none of
the above.

It's a shame that there really is no information schema for indexes in
that category.