MDEV-19955 make argument of handler::ha_write_row() const

MDEV-19486 and one more similar bug appeared because handler::write_row() interface
welcomes to modify buffer by storage engine. But callers are not ready for that
thus bugs are possible in future.

handler::write_row():
handler::ha_write_row(): make argument const

2 files changed, 2 insertions, 2 deletions

diff --git a/storage/blackhole/ha_blackhole.cc b/storage/blackhole/ha_blackhole.cc
index 3f770c7005e..1b64db142e0 100644
--- a/storage/blackhole/ha_blackhole.cc
+++ b/storage/blackhole/ha_blackhole.cc
@@ -117,7 +117,7 @@ const char *ha_blackhole::index_type(uint key_number)
                HA_KEY_ALG_RTREE) ? "RTREE" : "BTREE");
 }
 
-int ha_blackhole::write_row(uchar * buf)
+int ha_blackhole::write_row(const uchar * buf)
 {
   DBUG_ENTER("ha_blackhole::write_row");
   DBUG_RETURN(table->next_number_field ? update_auto_increment() : 0);
diff --git a/storage/blackhole/ha_blackhole.h b/storage/blackhole/ha_blackhole.h
index 0632c87c306..6ee30877b64 100644
--- a/storage/blackhole/ha_blackhole.h
+++ b/storage/blackhole/ha_blackhole.h
@@ -96,7 +96,7 @@ public:
                              THR_LOCK_DATA **to,
                              enum thr_lock_type lock_type);
 private:
-  virtual int write_row(uchar *buf);
+  virtual int write_row(const uchar *buf);
   virtual int update_row(const uchar *old_data, const uchar *new_data);
   virtual int delete_row(const uchar *buf);
 };