Fix thinko in BitmapAdjustPrefetchIterator.

Dilip Kumar

Discussion: http://postgr.es/m/CAFiTN-uKAvRhWprb0i-U9zFOekgQRRwqjP1wvOBsKZb-UEKbug@mail.gmail.com

src/backend/executor/nodeBitmapHeapscan.c

@@ -494,7 +494,7 @@ BitmapAdjustPrefetchIterator(BitmapHeapScanState *node,
 		SpinLockAcquire(&pstate->mutex);
 		if (pstate->prefetch_pages > 0)
 		{
-			node->prefetch_pages--;
+			pstate->prefetch_pages--;
 			SpinLockRelease(&pstate->mutex);
 		}
 		else