Re: pl/tcl function to detect when a request has been canceled

Andres Freund <andres@anarazel.de> writes:
> On 2018-06-08 18:08:14 +0000, Peter Da Silva wrote:
>> There is a C-level variable QueryCancelPending that can be used to
>> monitor for this case, but it’s not visible at the pl/tcl scripting
>> level. This is a simple new command that returns the current state of
>> this variable to Tcl.

> I'm not terribly opposed to this, but I wonder if the much more
> pragmatic solution is to just occasionally call a database function that
> checks this?  You could just run SELECT 1 occasionally :/

That would be quite expensive for the purpose, surely.

My complaint about it is more like "if we're going to put this into
pltcl, why not also plperl and plpython?"  It might be unfair to
ask this patch to cover all three, but it would be odd not to try to
maintain feature parity ... especially since pltcl is probably the
least-used of the three these days.

            regards, tom lane