Check for interrupts during tuple-insertion loops.

Normally, this won't matter too much; but if I/O is really slow, for
example because the system is overloaded, we might write many pages
before checking for interrupts.  A single toast insertion might
write up to 1GB of data, and a multi-insert could write hundreds
of tuples (and their corresponding TOAST data).

src/backend/access/heap/heapam.c

@@ -2355,6 +2355,8 @@ heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
 		bool		all_visible_cleared = false;
 		int			nthispage;
 
+		CHECK_FOR_INTERRUPTS();
+
 		/*
 		 * Find buffer where at least the next tuple will fit.  If the page is
 		 * all-visible, this will also pin the requisite visibility map page.

src/backend/access/heap/tuptoaster.c

@@ -35,6 +35,7 @@
 #include "access/tuptoaster.h"
 #include "access/xact.h"
 #include "catalog/catalog.h"
+#include "miscadmin.h"
 #include "utils/fmgroids.h"
 #include "utils/pg_lzcompress.h"
 #include "utils/rel.h"
@@ -1495,6 +1496,8 @@ toast_save_datum(Relation rel, Datum value,
 	{
 		int			i;
 
+		CHECK_FOR_INTERRUPTS();
+
 		/*
 		 * Calculate the size of this chunk
 		 */