Message-ID: <3fd9c2859c323d6f894ccf660764f24dc3423181.camel@cybertec.at>
Subject: Re: libpq simple SELECT
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Igor Korot <ikorot01@gmail.com>
Cc: "pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
Date: Wed, 17 Dec 2025 21:22:32 +0100
In-Reply-To: <CA+FnnTzWJtJwUjWBbm9naV9BUWdzTnQ8dKCtPOqaL0+1UOWcAQ@mail.gmail.com>
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On Wed, 2025-12-17 at 09:42 -0800, Igor Korot wrote:
> On Tue, Dec 16, 2025 at 11:34=E2=80=AFPM Laurenz Albe <laurenz.albe@cyber=
tec.at> wrote:
> > On Tue, 2025-12-16 at 21:49 -0800, Igor Korot wrote:
> > > I just tried the following code:
> > >=20
> > > [code]
> > > =C2=A0 =C2=A0 =C2=A0std::wstring query1 =3D L"SELECT t.table_catalog =
AS catalog,
> > > t.table_schema AS schema, t.table_name AS table, u.usename AS owner,
> > > c.oid AS table_id FROM information_schema.tables t,
> > > pg_catalog.pg_class c, pg_catalog.pg_user u WHERE t.table_name =3D
> > > c.relname AND c.relowner =3D usesysid AND (t.table_type =3D 'BASE TAB=
LE'
> > > OR t.table_type =3D 'VIEW' OR t.table_type =3D 'LOCAL TEMPORARY') ORD=
ER BY
> > > table_name;";
> > > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0res =3D PQexec( m_db, m_pimpl->m_my=
conv.to_bytes( query1.c_str()
> > > ).c_str() );
> > > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 for( int i =3D 0; i < PQntuples( r=
es ); i++ )
> > > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 {
> > > some code handling the results
> > > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 }
> > > [/code]
> > >=20
> > > The loop is executed exactly 1 time.
> > >=20
> > > My question is - according to the comment above I don't have to use c=
ursor,
> > > but it looks like it's unavoidable?
> >=20
> > I see no cursor in your example...
>=20
> That is my question.
>=20
> The code shows cursor but the comment indicate that the cursor is not req=
uired.

I am still confused.

You quoted a comment from a sample program in the documentation, and that
example is actually using a cursor:

    res =3D PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_data=
base");

But your code does not use a cursor.  So why should the comment apply to it=
?

Yours,
Laurenz Albe