[#MDEV-28668] Recovery or backup of INSERT may be incorrect

mleich produced rr record traces where a child page number in a B-tree record was recovered incorrectly. The culprit seems to be an overzealous optimization:

diff --git a/storage/innobase/page/page0cur.cc b/storage/innobase/page/page0cur.cc

index dc740cad862..d37d3d85f96 100644

--- a/storage/innobase/page/page0cur.cc

+++ b/storage/innobase/page/page0cur.cc

@@ -1579,8 +1579,12 @@ page_cur_insert_rec_low(

     const byte *r= rec;

     const byte *c= cur->rec;

     const byte *c_end= cur->rec + data_size;

+    static_assert(REC_N_OLD_EXTRA_BYTES == REC_N_NEW_EXTRA_BYTES + 1, "");

     if (c <= insert_buf && c_end > insert_buf)

       c_end= insert_buf;

+    else if (c_end < next_rec &&

+             c_end >= next_rec - REC_N_OLD_EXTRA_BYTES + comp)

+      c_end= next_rec - REC_N_OLD_EXTRA_BYTES + comp;

     else

       c_end= std::min<const byte*>(c_end, block->page.frame + srv_page_size -

                                    PAGE_DIR - PAGE_DIR_SLOT_SIZE *

That is, we would compare the bytes of the being-inserted record to some header bytes of next_rec that were just updated by the same function, without them being written to the redo log at all.

[MDEV-28668] Recovery or backup of INSERT may be incorrect Created: 2022-05-25 Updated: 2022-09-01 Resolved: 2022-05-25
Status:	Closed
Project:	MariaDB Server
Component/s:	Backup, Storage Engine - InnoDB
Affects Version/s:	10.5, 10.6, 10.7, 10.8, 10.9, 10.10
Fix Version/s:	10.5.17, 10.6.9, 10.7.5, 10.8.4, 10.9.2

[MDEV-28668] Recovery or backup of INSERT may be incorrect Created: 2022-05-25 Updated: 2022-09-01 Resolved: 2022-05-25