Re: Cancelling Requests Frontend/Backend Protocol TCP/IP

On 02/11/2009, at 17:53, Tom Lane wrote:

> Raimon Fernandez <coder@montx.com> writes:
>> The sentence 'backend has finished processing the query' means that
>> postgresql has finished processing the select and also has sent all
>> the rows ?
>
> There is no distinction; rows are sent as they are generated.

Yes, but  a SELECT can return 50000 rows, and as you say, postgresql
sends the rows as they are generated.

My question still remain unclear to me:

when postgres has finished processing the select, just before sending
the first row(1), in the middle(2), or at the end(3), when the last
row has been sent ?

If I send the CancelRequest when postgres is in point 3, I'm too late,
but if postgres is in 1 or 2, the CancelRequest will have some effect.

I'm still wrong here ?

thanks for clarification the concept!

regards,

raimon