Re: migration: parameterized statement and cursor

On 1/11/2010 8:16 AM, Aleksey Onopriyenko wrote:
> Hello.
>
> We are trying to migrate from Informix 9.4 to PostgreSQL. As part of
> migration we are porting our client application.
>
> So we need reimplement such functionality:
> 1. Declare a cursor using to _parameterized_ SELECT statement. It should
> be possible to specify cursor's name (and, perhaps, the statement)
> dynamically.
> 2. Open that cursor (in another C-function) passing parameters to it.
> 3. Fetch records from result set.
> 4. Close the cursor.
>
> Steps 2-4 may be repeated if necessary.
>
> Is it possible with ecpg or libpq?
>
> ----
> Best regards,
> Aleksey

You dont need cursors, really.

In code (a little sudo-code), do:

q := prepare('select f1, f2 from table_x where id = $1');

then you can pass it around as you like, until...

q.params[0] := 42;
q.open();

while not q.eof()
begin
print q.field[0].asString, "\n";
q.next();
end

This is NOT libpq sudo-code, its delphi'ish, which uses libpq under the
hood. My point being, you dont really need cursors, just prepare a
select statement, set it params, fire it off, iterate the result set...
done. And its re-useable.

Unless I missed your purpose.

-Andy