PQcancel

Function

PQcancel is used to request the server to abandon processing of the current command.

Prototype

int PQcancel(PGcancel* cancel, char* errbuf, int errbufsize);

Parameter

**Table 1** PQcancel parameters
Keyword	Parameter Description
cancel	Points to the object pointer that contains the cancel information.
errbuf	Buffer for storing error information.
errbufsize	Size of the buffer for storing error information.

Return Value

int indicates the execution result. 1 indicates successful execution and 0 indicates an execution failure. The failure cause is stored in errbuf.

Precautions

Successful sending does not guarantee that the request will have any effect. If the cancellation is valid, the current command is terminated early and an error is returned. If the cancellation fails (for example, because the server has processed the command), no result is returned.
If errbuf is a local variable in a signal handler, you can safely call PQcancel from the signal handler. For PQcancel, the PGcancel object is read-only, so it can also be called from a thread that is separate from the thread that is operating the PGconn object.