Update datafusion/src/execution/memory_manager.rs

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

Author: yjshen

datafusion/src/execution/memory_manager.rs

@@ -26,10 +26,10 @@ use std::fmt::{Debug, Display, Formatter};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::{Arc, Condvar, Mutex, Weak};
 
-static mut CONSUMER_ID: AtomicUsize = AtomicUsize::new(0);
+static CONSUMER_ID: AtomicUsize = AtomicUsize::new(0);
 
 fn next_id() -> usize {
-    unsafe { CONSUMER_ID.fetch_add(1, Ordering::SeqCst) }
+    CONSUMER_ID.fetch_add(1, Ordering::SeqCst)
 }
 
 /// Type of the memory consumer