Message-ID: <2bad53942920d2e501661af4cd49d6644a22b801.camel@cybertec.at>
Subject: Re: unnest multirange, returned order
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: daniel.fredouille@gmail.com, pgsql-docs@lists.postgresql.org
Date: Tue, 03 Oct 2023 15:46:23 +0200
In-Reply-To: <169627213477.3727338.17653654241633692682@wrigleys.postgresql.org>
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	<169627213477.3727338.17653654241633692682@wrigleys.postgresql.org>
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On Mon, 2023-10-02 at 18:42 +0000, PG Doc comments form wrote:
> Page: https://www.postgresql.org/docs/16/functions-range.html
>=20
> The doc says:
> * unnest ( anymultirange ) =E2=86=92 setof anyrange
> * Expands a multirange into a set of ranges. The ranges are read out in
> storage order (ascending).
>=20
> What is storage order ?=20
>=20
> At first I thought that it was the order in which the different ranges ar=
e
> inserted in the internal data structure. However, the following sort of
> shows that it is not:
> ```
> postgres=3D# select unnest('{[1,4), [8,10)}'::int4multirange + '{[-5,-3)}=
' -
> '{[2,3)}') ;
> =C2=A0unnest
> ---------
> =C2=A0[-5,-3)
> =C2=A0[1,2)
> =C2=A0[3,4)
> =C2=A0[8,10)
> (4 lignes)
> ```
> Whatever I try, it always return in range order instead of "storage order=
".

I'd say that the storag order is the order in which PostgreSQL stores
multiranges internally:

SELECT '{[100,200),[-100,-50),[-1,2)}'::int4multirange;

        int4multirange        =20
=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=
=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=
=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=
=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90=E2=95=90
 {[-100,-50),[-1,2),[100,200)}
(1 row)

Yours,
Laurenz Albe