Fix datatype confusion in logtape.c's right_offset().

This could only matter if (a) long is wider than int, and (b) the heap
of free blocks exceeds UINT_MAX entries, which seems pretty unlikely.
Still, it's a theoretical bug, so backpatch to v13 where the typo came
in (in commit c02fdc922).

In passing, also make swap_nodes() use consistent datatypes.

Ma Liangzhu

Discussion: https://postgr.es/m/17336-fc4e522d26a750fd@postgresql.org

src/backend/utils/sort/logtape.c

@@ -343,7 +343,7 @@ ltsReadFillBuffer(LogicalTapeSet *lts, LogicalTape *lt)
 static inline void
 swap_nodes(long *heap, unsigned long a, unsigned long b)
 {
-	unsigned long swap;
+	long		swap;
 
 	swap = heap[a];
 	heap[a] = heap[b];
@@ -357,7 +357,7 @@ left_offset(unsigned long i)
 }
 
 static inline unsigned long
-right_offset(unsigned i)
+right_offset(unsigned long i)
 {
 	return 2 * i + 2;
 }