branches/zip: btr_cur_t: replace left_page with left_block, to avoid

calling buf_block_align() in btr_pcur_move_backward_from_page().
Also, enclose some assertions about page_is_comp() in #ifdef UNIV_BTR_DEBUG.

btr/btr0cur.c

@@ -188,7 +188,9 @@ btr_cur_latch_leaves(
 	case BTR_MODIFY_LEAF:
 		mode = latch_mode == BTR_SEARCH_LEAF ? RW_S_LATCH : RW_X_LATCH;
 		get_block = btr_block_get(space, page_no, mode, mtr);
+#ifdef UNIV_BTR_DEBUG
 		ut_a(page_is_comp(get_block->frame) == page_is_comp(page));
+#endif /* UNIV_BTR_DEBUG */
 		get_block->check_index_page_at_flush = TRUE;
 		return;
 	case BTR_MODIFY_TREE:
@@ -208,7 +210,9 @@ btr_cur_latch_leaves(
 		}
 
 		get_block = btr_block_get(space, page_no, RW_X_LATCH, mtr);
+#ifdef UNIV_BTR_DEBUG
 		ut_a(page_is_comp(get_block->frame) == page_is_comp(page));
+#endif /* UNIV_BTR_DEBUG */
 		get_block->check_index_page_at_flush = TRUE;
 
 		right_page_no = btr_page_get_next(page, mtr);
@@ -236,18 +240,20 @@ btr_cur_latch_leaves(
 		if (left_page_no != FIL_NULL) {
 			get_block = btr_block_get(space, left_page_no,
 						  mode, mtr);
-			cursor->left_page = buf_block_get_frame(get_block);
+			cursor->left_block = get_block;
 #ifdef UNIV_BTR_DEBUG
-			ut_a(page_is_comp(cursor->left_page)
+			ut_a(page_is_comp(get_block->frame)
 			     == page_is_comp(page));
-			ut_a(btr_page_get_next(cursor->left_page, mtr)
+			ut_a(btr_page_get_next(get_block->frame, mtr)
 			     == page_get_page_no(page));
 #endif /* UNIV_BTR_DEBUG */
 			get_block->check_index_page_at_flush = TRUE;
 		}
 
 		get_block = btr_block_get(space, page_no, mode, mtr);
+#ifdef UNIV_BTR_DEBUG
 		ut_a(page_is_comp(get_block->frame) == page_is_comp(page));
+#endif /* UNIV_BTR_DEBUG */
 		get_block->check_index_page_at_flush = TRUE;
 		return;
 	}
@@ -281,7 +287,7 @@ btr_cur_search_to_nth_level(
 				PAGE_CUR_LE to search the position! */
 	ulint		latch_mode, /* in: BTR_SEARCH_LEAF, ..., ORed with
 				BTR_INSERT and BTR_ESTIMATE;
-				cursor->left_page is used to store a pointer
+				cursor->left_block is used to store a pointer
 				to the left neighbor page, in the cases
 				BTR_SEARCH_PREV and BTR_MODIFY_PREV;
 				NOTE that if has_search_latch

btr/btr0pcur.c

@@ -434,7 +434,7 @@ btr_pcur_move_backward_from_page(
 	ulint		prev_page_no;
 	ulint		space;
 	page_t*		page;
-	page_t*	prev_page;
+	buf_block_t*	prev_block;
 	ulint		latch_mode;
 	ulint		latch_mode2;
 
@@ -473,14 +473,13 @@ btr_pcur_move_backward_from_page(
 	if (prev_page_no == FIL_NULL) {
 	} else if (btr_pcur_is_before_first_on_page(cursor, mtr)) {
 
-		prev_page = btr_pcur_get_btr_cur(cursor)->left_page;
+		prev_block = btr_pcur_get_btr_cur(cursor)->left_block;
 
 		btr_leaf_page_release(btr_pcur_get_block(cursor),
 				      latch_mode, mtr);
 
-		btr_pcur_get_btr_cur(cursor)->page_block
-			= buf_block_align(prev_page);
-		page_cur_set_after_last(prev_page,
+		btr_pcur_get_btr_cur(cursor)->page_block = prev_block;
+		page_cur_set_after_last(buf_block_get_frame(prev_block),
 					btr_pcur_get_page_cur(cursor));
 	} else {
 
@@ -488,10 +487,9 @@ btr_pcur_move_backward_from_page(
 		a page. Cursor repositioning acquired a latch also on the
 		previous page, but we do not need the latch: release it. */
 
-		prev_page = btr_pcur_get_btr_cur(cursor)->left_page;
+		prev_block = btr_pcur_get_btr_cur(cursor)->left_block;
 
-		btr_leaf_page_release(buf_block_align(prev_page),
-				      latch_mode, mtr);
+		btr_leaf_page_release(prev_block, latch_mode, mtr);
 	}
 
 	cursor->latch_mode = latch_mode;

include/btr0cur.h

@@ -118,7 +118,7 @@ btr_cur_search_to_nth_level(
 				search the position! */
 	ulint		latch_mode, /* in: BTR_SEARCH_LEAF, ..., ORed with
 				BTR_INSERT and BTR_ESTIMATE;
-				cursor->left_page is used to store a pointer
+				cursor->left_block is used to store a pointer
 				to the left neighbor page, in the cases
 				BTR_SEARCH_PREV and BTR_MODIFY_PREV;
 				NOTE that if has_search_latch
@@ -598,7 +598,7 @@ struct btr_cur_struct {
 	buf_block_t*	page_block;	/* buffer pool block were
 					cursor is positioned; needed
 					to avoid buf_block_align() */
-	page_t*		left_page;	/* this field is used to store
+	buf_block_t*	left_block;	/* this field is used to store
 					a pointer to the left neighbor
 					page, in the cases
 					BTR_SEARCH_PREV and