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From: Igor Korot <ikorot01@gmail.com>
Date: Wed, 17 Dec 2025 09:42:09 -0800
Message-ID: <CA+FnnTzWJtJwUjWBbm9naV9BUWdzTnQ8dKCtPOqaL0+1UOWcAQ@mail.gmail.com>
Subject: Re: libpq simple SELECT
To: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: "pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
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Lauren=E2=80=99s,,

On Tue, Dec 16, 2025 at 11:34=E2=80=AFPM Laurenz Albe <laurenz.albe@cyberte=
c.at>
wrote:

> On Tue, 2025-12-16 at 21:49 -0800, Igor Korot wrote:
> > I just tried the following code:
> >
> > [code]
> >     std::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 TABLE=
'
> > OR t.table_type =3D 'VIEW' OR t.table_type =3D 'LOCAL TEMPORARY') ORDER=
 BY
> > table_name;";
> >         res =3D PQexec( m_db, m_pimpl->m_myconv.to_bytes( query1.c_str(=
)
> > ).c_str() );
> >          for( int i =3D 0; i < PQntuples( res ); i++ )
> >          {
> > some code handling the results
> >          }
> > [/code]
> >
> > The loop is executed exactly 1 time.
> >
> > My question is - according to the comment above I don't have to use
> cursor,
> > but it looks like it's unavoidable?
>
> I see no cursor in your example...


That is my question.

The code shows cursor but the comment indicate that the cursor is not
required.

So do I have to use it? And if not - how to get the results?

Thank you.


>
> Yours,
> Laurenz Albe
>

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<div dir=3D"auto">Lauren=E2=80=99s,,</div><div><br><div class=3D"gmail_quot=
e gmail_quote_container"><div dir=3D"ltr" class=3D"gmail_attr">On Tue, Dec =
16, 2025 at 11:34=E2=80=AFPM Laurenz Albe &lt;<a href=3D"mailto:laurenz.alb=
e@cybertec.at">laurenz.albe@cybertec.at</a>&gt; wrote:<br></div><blockquote=
 class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc soli=
d;padding-left:1ex">On Tue, 2025-12-16 at 21:49 -0800, Igor Korot wrote:<br=
>
&gt; I just tried the following code:<br>
&gt; <br>
&gt; [code]<br>
&gt;=C2=A0 =C2=A0 =C2=A0std::wstring query1 =3D L&quot;SELECT t.table_catal=
og AS catalog,<br>
&gt; t.table_schema AS schema, t.table_name AS table, u.usename AS owner,<b=
r>
&gt; c.oid AS table_id FROM information_schema.tables t,<br>
&gt; pg_catalog.pg_class c, pg_catalog.pg_user u WHERE t.table_name =3D<br>
&gt; c.relname AND c.relowner =3D usesysid AND (t.table_type =3D &#39;BASE =
TABLE&#39;<br>
&gt; OR t.table_type =3D &#39;VIEW&#39; OR t.table_type =3D &#39;LOCAL TEMP=
ORARY&#39;) ORDER BY<br>
&gt; table_name;&quot;;<br>
&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0res =3D PQexec( m_db, m_pimpl-&gt;m_m=
yconv.to_bytes( query1.c_str()<br>
&gt; ).c_str() );<br>
&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 for( int i =3D 0; i &lt; PQntuples( =
res ); i++ )<br>
&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 {<br>
&gt; some code handling the results<br>
&gt;=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 }<br>
&gt; [/code]<br>
&gt; <br>
&gt; The loop is executed exactly 1 time.<br>
&gt; <br>
&gt; My question is - according to the comment above I don&#39;t have to us=
e cursor,<br>
&gt; but it looks like it&#39;s unavoidable?<br>
<br>
I see no cursor in your example...</blockquote><div dir=3D"auto"><br></div>=
<div dir=3D"auto">That is my question.</div><div dir=3D"auto"><br></div><di=
v dir=3D"auto">The code shows cursor but the comment indicate that the curs=
or is not required.</div><div dir=3D"auto"><br></div><div dir=3D"auto">So d=
o I have to use it? And if not - how to get the results?</div><div dir=3D"a=
uto"><br></div><div dir=3D"auto">Thank you.</div><div dir=3D"auto"><br></di=
v><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:=
1px #ccc solid;padding-left:1ex" dir=3D"auto"><br>
<br>
Yours,<br>
Laurenz Albe<br>
</blockquote></div></div>

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