Help Center/ GaussDB/ Developer Guide(Distributed_3.x)/ Application Development Guide/ Development Based on libpq/ libpq Interface Reference/ Functions for Canceling Queries in Progress/ PQcancel
Updated on 2024-05-07 GMT+08:00
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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.