Re: BUG #13518: CancelRequest lacks statement identifier

"niallfr@btinternet.com" <niallfr@btinternet.com> wrote:

> If CancelRequest could include a statement name (or other means
> of identifying a statement) and did nothing if that statement was
> no longer running by the time the server processed it, the
> usability of CancelRequest would be significantly enhanced.

Would it be sufficient for your purposes to cancel a *transaction*
rather than a *statement*?  There is already a virtual transaction
ID exposed in pg_locks, and it could probably be added to
pg_stat_activity; we could probably create a
pg_cancel_transaction() function that took a text representation of
that and only canceled the transaction if it was running.  There
would need to be locking on a heavily contended lock or two to make
that happen correctly, but presumably this would not ba a
high-volume activity.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company