Add some const qualifications

Add some const qualifications afforded by the previous change that
added a const qualification to PageAddItemExtended().

Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Discussion: https://www.postgresql.org/message-id/flat/c75cccf5-5709-407b-a36a-2ae6570be766@eisentraut.org

src/backend/access/brin/brin_pageops.c

@@ -340,7 +340,7 @@ brin_can_do_samepage_update(Buffer buffer, Size origsz, Size newsz)
 OffsetNumber
 brin_doinsert(Relation idxrel, BlockNumber pagesPerRange,
 			  BrinRevmap *revmap, Buffer *buffer, BlockNumber heapBlk,
-			  BrinTuple *tup, Size itemsz)
+			  const BrinTuple *tup, Size itemsz)
 {
 	Page		page;
 	BlockNumber blk;

src/backend/access/gin/ginfast.c

@@ -57,7 +57,7 @@ typedef struct KeyArray
  */
 static int32
 writeListPage(Relation index, Buffer buffer,
-			  IndexTuple *tuples, int32 ntuples, BlockNumber rightlink)
+			  const IndexTuple *tuples, int32 ntuples, BlockNumber rightlink)
 {
 	Page		page = BufferGetPage(buffer);
 	int32		i,

src/backend/access/nbtree/nbtinsert.c

@@ -61,7 +61,7 @@ static Buffer _bt_split(Relation rel, Relation heaprel, BTScanInsert itup_key,
 static void _bt_insert_parent(Relation rel, Relation heaprel, Buffer buf,
 							  Buffer rbuf, BTStack stack, bool isroot, bool isonly);
 static Buffer _bt_newlevel(Relation rel, Relation heaprel, Buffer lbuf, Buffer rbuf);
-static inline bool _bt_pgaddtup(Page page, Size itemsize, IndexTuple itup,
+static inline bool _bt_pgaddtup(Page page, Size itemsize, const IndexTupleData *itup,
 								OffsetNumber itup_off, bool newfirstdataitem);
 static void _bt_delete_or_dedup_one_page(Relation rel, Relation heapRel,
 										 BTInsertState insertstate,
@@ -2634,7 +2634,7 @@ _bt_newlevel(Relation rel, Relation heaprel, Buffer lbuf, Buffer rbuf)
 static inline bool
 _bt_pgaddtup(Page page,
 			 Size itemsize,
-			 IndexTuple itup,
+			 const IndexTupleData *itup,
 			 OffsetNumber itup_off,
 			 bool newfirstdataitem)
 {

src/backend/access/nbtree/nbtsort.c

@@ -266,7 +266,7 @@ static BulkWriteBuffer _bt_blnewpage(BTWriteState *wstate, uint32 level);
 static BTPageState *_bt_pagestate(BTWriteState *wstate, uint32 level);
 static void _bt_slideleft(Page rightmostpage);
 static void _bt_sortaddtup(Page page, Size itemsize,
-						   IndexTuple itup, OffsetNumber itup_off,
+						   const IndexTupleData *itup, OffsetNumber itup_off,
 						   bool newfirstdataitem);
 static void _bt_buildadd(BTWriteState *wstate, BTPageState *state,
 						 IndexTuple itup, Size truncextra);
@@ -716,7 +716,7 @@ _bt_slideleft(Page rightmostpage)
 static void
 _bt_sortaddtup(Page page,
 			   Size itemsize,
-			   IndexTuple itup,
+			   const IndexTupleData *itup,
 			   OffsetNumber itup_off,
 			   bool newfirstdataitem)
 {

src/include/access/brin_pageops.h

@@ -23,7 +23,7 @@ extern bool brin_can_do_samepage_update(Buffer buffer, Size origsz,
 										Size newsz);
 extern OffsetNumber brin_doinsert(Relation idxrel, BlockNumber pagesPerRange,
 								  BrinRevmap *revmap, Buffer *buffer, BlockNumber heapBlk,
-								  BrinTuple *tup, Size itemsz);
+								  const BrinTuple *tup, Size itemsz);
 
 extern void brin_page_init(Page page, uint16 type);
 extern void brin_metapage_init(Page page, BlockNumber pagesPerRange,