MDEV-22866: Server crashes in ... with not_null_range_scan=onbb-10.3-mdev22866

Starting from 10.3, the optimizer is able to detect that entire outer join
nests are constants (because of "Impossible ON") and remove them (see
mark_join_nest_as_const)

However, this was not properly accounted for in NESTED_JOIN structure
and the way check_interleaving_with_nj() uses its n_tables member to
check if the join prefix order is allowed.

(The result was that the optimizer could conclude that no join prefix is
allowed and fail an assertion)

1 files changed, 4 insertions, 2 deletions

diff --git a/sql/table.h b/sql/table.h
index 2bad6cbf32f..d289b6e0ab2 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -2932,9 +2932,11 @@ typedef struct st_nested_join
     Before each use the counters are zeroed by reset_nj_counters.
   */
   uint              counter;
+
   /*
-    Number of elements in join_list that were not (or contain table(s) that 
-    weren't) removed by table elimination.
+    Number of elements in join_list that participate in the join plan choice:
+    - Base tables that were not removed by table elimination
+    - Join nests that were not removed by mark_join_nest_as_const
   */
   uint              n_tables;
   nested_join_map   nj_map;          /* Bit used to identify this nested join*/