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From: Laurenz Albe <[email protected]>
To: Igor Korot <[email protected]>
Cc: pgsql-generallists.postgresql.org <[email protected]>
Subject: Re: libpq simple SELECT
Date: Wed, 17 Dec 2025 21:22:32 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+FnnTzWJtJwUjWBbm9naV9BUWdzTnQ8dKCtPOqaL0+1UOWcAQ@mail.gmail.com>
References: <CA+FnnTzP_9Mh9S7NJL5WFJmbOi2wxw4g=MdoUo-SuXEp3Fyg-g@mail.gmail.com>
	<[email protected]>
	<CA+FnnTzWJtJwUjWBbm9naV9BUWdzTnQ8dKCtPOqaL0+1UOWcAQ@mail.gmail.com>

On Wed, 2025-12-17 at 09:42 -0800, Igor Korot wrote:
> On Tue, Dec 16, 2025 at 11:34 PM Laurenz Albe <[email protected]> wrote:
> > On Tue, 2025-12-16 at 21:49 -0800, Igor Korot wrote:
> > > I just tried the following code:
> > > 
> > > [code]
> > >      std::wstring query1 = 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 =
> > > c.relname AND c.relowner = usesysid AND (t.table_type = 'BASE TABLE'
> > > OR t.table_type = 'VIEW' OR t.table_type = 'LOCAL TEMPORARY') ORDER BY
> > > table_name;";
> > >          res = PQexec( m_db, m_pimpl->m_myconv.to_bytes( query1.c_str()
> > > ).c_str() );
> > >           for( int i = 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.

I am still confused.

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

    res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");

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

Yours,
Laurenz Albe

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