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From: jian he <jian.universality@gmail.com>
Date: Fri, 12 Sep 2025 21:53:34 +0800
Message-ID: <CACJufxHQA5HubHV88SztwENPyibfSBJ3wZNBDbJoR6svxmEGCw@mail.gmail.com>
Subject: Re: Latest patches break one of our unit-test, related to RLS
To: Dominique Devienne <ddevienne@gmail.com>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>, pgsql-general@postgresql.org
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On Fri, Sep 12, 2025 at 9:35=E2=80=AFPM Dominique Devienne <ddevienne@gmail=
.com> wrote:
>
> On Fri, Sep 12, 2025 at 3:29=E2=80=AFPM Dominique Devienne <ddevienne@gma=
il.com> wrote:
> > On Fri, Sep 12, 2025 at 3:24=E2=80=AFPM Dominique Devienne <ddevienne@g=
mail.com> wrote:
> > > On Fri, Sep 12, 2025 at 3:11=E2=80=AFPM Dominique Devienne <ddevienne=
@gmail.com> wrote:
> >
> > > So I don't see how my `... where v similar to 'foo[\d\w]_%'` is incor=
rect.
> > > So again, is this a bug / regression or not? Thanks, --DD
> >
> > If I use (x|y) instead of [xy] it seems to behave correctly.
> > Whether x is the full-length POSIX class, or the shorthand notation.
> > This DOES look like a bug, no? I've done regexes for a long time,
> > and these two forms should be equivalent IMHO. --DD
> >
> > postgres=3D# show server_version;
> >  server_version
> > ----------------
> >  18rc1
> > (1 row)
> >
> >
> > postgres=3D# with t(v) as (values ('foo:bar'), ('foo/bar'), ('foo0bar')=
)
> > select v from t where v similar to 'foo[\d\w]_%';
> >  v
> > ---
> > (0 rows)
> >
> >
> > postgres=3D# with t(v) as (values ('foo:bar'), ('foo/bar'), ('foo0bar')=
)
> > select v from t where v similar to 'foo[[[:digit:]][[:word:]]]_%';
> >  v
> > ---
> > (0 rows)
> >

The above two examples are the same, per
(Table 9.21. Regular Expression Class-Shorthand Escapes)
https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-S=
IMILARTO-REGEXP

my guess why 'foo0bar' will fail for 'foo[[[:digit:]][[:word:]]]_%';
1. process character 0, it does meet [[:digits]] character class.
2. process character b, it does not meet [[:digits]], then fails,
it won't check again whether character b is satisfied with [[:word:]] or no=
t.