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From: Laurenz Albe <[email protected]>
To: Igor Korot <[email protected]>
To: Christophe Pettus <[email protected]>
Cc: Adrian Klaver <[email protected]>
Cc: pgsql-generallists.postgresql.org <[email protected]>
Subject: Re: Get info about the index
Date: Sat, 26 Jul 2025 21:50:20 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+FnnTy8bdXxFZBmFfm1oNMQLVxL-+UmkX8EecbLB0MehX8gFw@mail.gmail.com>
References: <CA+FnnTw2ouEQKSKzQ_SNo8efWE8wEqjr9Ux-F-wbR+y=Pn6bGg@mail.gmail.com>
	<[email protected]>
	<CA+FnnTyKb0cLp9GF3YENoBZ4LVW3db_RSGR99BPFnA4BZtc8kQ@mail.gmail.com>
	<[email protected]>
	<CA+FnnTy8bdXxFZBmFfm1oNMQLVxL-+UmkX8EecbLB0MehX8gFw@mail.gmail.com>

On Sat, 2025-07-26 at 15:13 -0400, Igor Korot wrote:
> On Sat, Jul 26, 2025, 2:14 PM Christophe Pettus <[email protected]> wrote:
> > > I want to know all individual things:
> > > - whether the index is unique.
> > > - what type of index it is
> > > - whether the field is ASC or DESC.
> > > - all other individual arams
> > 
> > pg_index is the source for those.  The one exception is the access method for the index, which is in pg_class.
> 
> I didn't find the sorting for the field.

That's in pg_index.indoption.

The flags stored there are defined in src/include/catalog/pg_index.h

/*
 * Index AMs that support ordered scans must support these two indoption
 * bits.  Otherwise, the content of the per-column indoption fields is
 * open for future definition.
 */
#define INDOPTION_DESC          0x0001  /* values are in reverse order */
#define INDOPTION_NULLS_FIRST   0x0002  /* NULLs are first instead of last */

So a value of 3 would mean DESC NULLS FIRST.

Yours,
Laurenz Albe

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