pgsql: Handle cancel requests with PID 0 gracefully

Handle cancel requests with PID 0 gracefully If the client sent a query cancel request with backend PID 0, it tripped an assertion. With assertions disabled, you got this in the log instead: LOG: invalid cancel request with PID 0 LOG: wrong key in cancel request for process 0 Query can

pgsql: Handle cancel requests with PID 0 gracefully

Handle cancel requests with PID 0 gracefully If the client sent a query cancel request with backend PID 0, it tripped an assertion. With assertions disabled, you got this in the log instead: LOG: invalid cancel request with PID 0 LOG: wrong key in cancel request for process 0 Query can