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From: Igor Korot <ikorot01@gmail.com>
Date: Tue, 29 Jul 2025 07:18:15 -0500
Message-ID: <CA+FnnTzGZwjg5jJRVwMX_TyRpW+bJZAyN3EFv7qFv56_RfbFjw@mail.gmail.com>
Subject: Re: Get info about the index
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: David Barbour <david.barbour@amiralearning.com>, Jon Zeppieri <zeppieri@gmail.com>, 
	Christophe Pettus <xof@thebuild.com>, Adrian Klaver <adrian.klaver@aklaver.com>, 
	"pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
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On Tue, Jul 29, 2025 at 7:07=E2=80=AFAM Laurenz Albe <laurenz.albe@cybertec=
.at> wrote:
>
> On Tue, 2025-07-29 at 06:46 -0500, Igor Korot wrote:
> > SELECT
> >     t.relname AS table_name,
> >     i.relname AS index_name,
> >     a.attname AS column_name
> > FROM
> >     pg_class t,
> >     pg_class i,
> >     pg_index ix,
> >     pg_attribute a
> > WHERE
> >     t.oid =3D ix.indrelid AND
> >     i.oid =3D ix.indexrelid AND
> >     a.attrelid =3D t.oid AND
> >     a.attnum =3D ANY(ix.indkey) AND
> >     t.relkind =3D 'r' AND -- 'r' for regular table
> >     t.relname =3D 'your_table_name' -- Optional: filter by table name
> > ORDER BY
> >     t.relname,
> >     i.relname,
> >     a.attnum;
> >
> > I can build on top of this query, however I have 2 issues:
> >
> > First and most important one - they are filtering by just table name.
> > How can I filter by the fully qualified name - catalog.schema.table?
>
> "catalog" is irrelevant, since PostgreSQL doesn't allow cross-database qu=
eries.

The reason I'm asking this is because I want to have the same
interface for different DBMSes.

But it also made me curious.

If I have a database for some financial data for the year 2024 in the
mydb_2024 and I have current year financial data in the mydb_2025 how
can I compare the data?

>
> To add a filter for the schema, use
>
>    AND t.relnamespace =3D 'schemaname'::regnamespace
>
> > Second - how cn I get the partial index condition? Either the whole
> > WHERE clause (which I will have to parse)
> > or the broken down one (field, condition {AND|OR} field, condition}?
>
>    SELECT pg_get_expr(ix.indpred, t.oid)
>
> Yours,
> Laurenz Albe

Thank you.