Function pg_resqueue_status

src/backend/utils/resscheduler/resqueue.c:1982–2084

* pg_resqueue_status - produce a view with one row per resource queue * showing internal information (counter values, waiters, holders). */

 *	showing internal information (counter values, waiters, holders).
 */
Datum
pg_resqueue_status(PG_FUNCTION_ARGS)
{
	FuncCallContext *funcctx = NULL;
	Datum		result;
	MemoryContext oldcontext = NULL;
	QueueStatusContext *fctx = NULL;	/* User function context. */
	HeapTuple	tuple = NULL;

	if (SRF_IS_FIRSTCALL())
	{

		funcctx = SRF_FIRSTCALL_INIT();

		/* Switch context when allocating stuff to be used in later calls */
		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

		fctx = (QueueStatusContext *) palloc(sizeof(QueueStatusContext));

		/*
		 * Allocate space for the per-call area - this overestimates, but
		 * means we can take the resource rescheduler lock after our memory
		 * context switching.
		 */
		fctx->record = (QueueStatusRec *) palloc(sizeof(QueueStatusRec) * MaxResourceQueues);

		funcctx->user_fctx = fctx;

		/* Construct a tuple descriptor for the result rows. */
		TupleDesc	tupledesc = CreateTemplateTupleDesc(PG_RESQUEUE_STATUS_COLUMNS);

		TupleDescInitEntry(tupledesc, (AttrNumber) 1, "queueid", OIDOID, -1, 0);
		TupleDescInitEntry(tupledesc, (AttrNumber) 2, "queuecountvalue", FLOAT4OID, -1, 0);
		TupleDescInitEntry(tupledesc, (AttrNumber) 3, "queuecostvalue", FLOAT4OID, -1, 0);
		TupleDescInitEntry(tupledesc, (AttrNumber) 4, "queuewaiters", INT4OID, -1, 0);
		TupleDescInitEntry(tupledesc, (AttrNumber) 5, "queueholders", INT4OID, -1, 0);

		funcctx->tuple_desc = BlessTupleDesc(tupledesc);

		/* Return to original context when allocating transient memory */
		MemoryContextSwitchTo(oldcontext);

		if (IsResQueueEnabled())
		{
			/* Get a snapshot of current state of resource queues */
			BuildQueueStatusContext(fctx);

			funcctx->max_calls = fctx->numRecords;
		}
		else
		{
			funcctx->max_calls = fctx->numRecords = 0;
		}
	}

	funcctx = SRF_PERCALL_SETUP();

	/* Get the saved state. */