Function AggRegisterCallback

src/backend/executor/nodeAgg.c:5037–5052

* AggRegisterCallback - register a cleanup callback for an aggregate * * This is useful for aggs to register shutdown callbacks, which will ensure * that non-memory resources are freed. The callback will occur just before * the associated aggcontext (as returned by AggCheckCallContext) is reset, * either between groups or as a result of rescanning the query. The callback * will NOT be call

 * As above, this is currently not useful for aggs called as window functions.
 */
void
AggRegisterCallback(FunctionCallInfo fcinfo,
					ExprContextCallbackFunction func,
					Datum arg)
{
	if (fcinfo->context && IsA(fcinfo->context, AggState))
	{
		AggState   *aggstate = (AggState *) fcinfo->context;
		ExprContext *cxt = aggstate->curaggcontext;

		RegisterExprContextCallback(cxt, func, arg);

		return;
	}
	elog(ERROR, "aggregate function cannot register a callback in this context");
}


/* ----------------------------------------------------------------