MDEV-28797 Assertion `page_rec_is_user_rec(rec)' failed in PageBulk::getSplitRec

- During alter operation of compressed table, page split operation
chooses the first record of the page as split record and it leads
to empty left page. This issue caused by the commit 77b3959b (MDEV-28457).

page_rec_is_second(), page_rec_is_second_last(): Removed the functions
since it is a deadcode.

storage/innobase/btr/btr0bulk.cc

@@ -634,7 +634,7 @@ PageBulk::getSplitRec()
 		 < total_used_size / 2);
 
 	/* Keep at least one record on left page */
-	if (page_rec_is_second(rec, m_page)) {
+	if (page_rec_is_first(rec, m_page)) {
 		rec = page_rec_get_next(rec);
 		ut_ad(page_rec_is_user_rec(rec));
 	}

storage/innobase/include/page0page.h

@@ -794,17 +794,6 @@ page_rec_is_first(
 	const page_t*	page)	/*!< in: page */
 	MY_ATTRIBUTE((warn_unused_result));
 
-/************************************************************//**
-true if the record is the second user record on a page.
-@return true if the second user record */
-UNIV_INLINE
-bool
-page_rec_is_second(
-/*===============*/
-	const rec_t*	rec,	/*!< in: record */
-	const page_t*	page)	/*!< in: page */
-	MY_ATTRIBUTE((warn_unused_result));
-
 /************************************************************//**
 true if the record is the last user record on a page.
 @return true if the last user record */
@@ -816,17 +805,6 @@ page_rec_is_last(
 	const page_t*	page)	/*!< in: page */
 	MY_ATTRIBUTE((warn_unused_result));
 
-/************************************************************//**
-true if the record is the second last user record on a page.
-@return true if the second last user record */
-UNIV_INLINE
-bool
-page_rec_is_second_last(
-/*====================*/
-	const rec_t*	rec,	/*!< in: record */
-	const page_t*	page)	/*!< in: page */
-	MY_ATTRIBUTE((warn_unused_result));
-
 /************************************************************//**
 Returns the maximum combined size of records which can be inserted on top
 of record heap.

storage/innobase/include/page0page.inl

@@ -192,22 +192,6 @@ page_rec_is_first(
 	return(page_rec_get_next_const(page_get_infimum_rec(page)) == rec);
 }
 
-/************************************************************//**
-true if the record is the second user record on a page.
-@return true if the second user record */
-UNIV_INLINE
-bool
-page_rec_is_second(
-/*===============*/
-	const rec_t*	rec,	/*!< in: record */
-	const page_t*	page)	/*!< in: page */
-{
-  ut_ad(page_get_n_recs(page) > 1);
-  if (const rec_t *first= page_rec_get_next_const(page_get_infimum_rec(page)))
-    return page_rec_get_next_const(first) == rec;
-  return false;
-}
-
 /************************************************************//**
 true if the record is the last user record on a page.
 @return true if the last user record */
@@ -223,24 +207,6 @@ page_rec_is_last(
 	return(page_rec_get_next_const(rec) == page_get_supremum_rec(page));
 }
 
-/************************************************************//**
-true if the record is the second last user record on a page.
-@return true if the second last user record */
-UNIV_INLINE
-bool
-page_rec_is_second_last(
-/*====================*/
-	const rec_t*	rec,	/*!< in: record */
-	const page_t*	page)	/*!< in: page */
-{
-  ut_ad(page_get_n_recs(page) > 1);
-  ut_ad(!page_rec_is_last(rec, page));
-
-  if (const rec_t *next= page_rec_get_next_const(rec))
-    return page_rec_is_supremum(page_rec_get_next_const(next));
-  return false;
-}
-
 /************************************************************//**
 Returns the middle record of the records on the page. If there is an
 even number of records in the list, returns the first record of the