Message-ID: <488788bd2526cec7eb175741c010cab2fa24fed4.camel@cybertec.at>
Subject: Re: Suggestion for docs, section "4.2.3 Subscripts": bounds and base
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: s@xss.de, pgsql-docs@lists.postgresql.org
Date: Mon, 07 Apr 2025 10:03:47 +0200
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On Thu, 2025-04-03 at 18:22 +0000, PG Doc comments form wrote:
> Page: https://www.postgresql.org/docs/17/sql-expressions.html
> Description:
>=20
> I skimmed over section 4.2 while waiting for a meeting to start and found=
 no
> mention of the following two questions that immediately pop up in my mind
> when subscripts are mentionned:
>=20
> Are subscripts 0-based or 1-based?

This question is answered in the documentation of the array data types:
https://www.postgresql.org/docs/current/arrays.html

  The array subscript numbers are written within square brackets. By defaul=
t
  PostgreSQL uses a one-based numbering convention for arrays, that is, an
  array of n elements starts with array[1] and ends with array[n].

> Are slice boundaries inclusive or exclusive?

That becomes clear on the same page:

  We can also access arbitrary rectangular slices of an array, or subarrays=
.
  An array slice is denoted by writing lower-bound:upper-bound for one or
  more array dimensions. For example, this query retrieves the first item
  on Bill's schedule for the first two days of the week:

    SELECT schedule[1:2][1:1] FROM sal_emp WHERE name =3D 'Bill';

            schedule
    ------------------------
     {{meeting},{training}}
    (1 row)

Admittedly, there is no exact definition, but the example makes clear that
the boundaries are inclusive.

I don't think that we need to repeat that information.

Yours,
Laurenz Albe