Re: libpq: How are result sets fetched behind the scene?

Sorry must read "fetched" in title.

Similar question:

When execution a SELECT (returning a large result set):

Is the whole result set fetched to the client app, not matter what row number is provided to the first PQgetvalue()
call(or similar API call on 
 
result set data or meta-data)?

Seb

On 8/29/19 6:32 PM, Sebastien FLAESCH wrote:
> Hi all,
> 
> We are using libpq in our C program.
> 
> I was wondering how the client lib / protocol manage to fetch the result set to the client app memory.
> 
> Is there some optimization ?
> 
> Are rows fetched in sequence until the requested row?
> 
> I mean if I do a SELECT that produces a huge result set, and then call PQgetvalue() with a row_number = 5000, are all
5000rows fetched from the 
 
> server or is there some smart fast-forward done because I did not ask the 4999 previous rows?
> 
> We know about server cursors (declare + fetch forward), and we do already fetch blocks of rows with this.
> 
> But server cursors are slow (and certainly use more server resources), compared to direct SELECT execution.
> 
> So we are wondering what would be the impact in terms of resources on the client application.
> 
> Is there any doc link or blog that would explain best practices with libpq result set programming?
> 
> Thanks!
> Seb
> 
>