Assertion failure with UPDATE of view using MERGE table

The problem was caused by an assertion that is not valid anymore.

mysql-test/main/merge.result

@@ -3898,9 +3898,6 @@ DROP TABLE t1;
 DROP TABLE m1;
 set global default_storage_engine=@save_default_storage_engine;
 #
-# End of 10.0 tests
-#
-#
 # MDEV-27407 Different ASC/DESC index attributes on MERGE and underlying table can cause wrong results
 #
 create table t (a int, key(a desc)) engine=myisam;
@@ -3967,3 +3964,12 @@ DROP TABLE tm, t1, t2;
 #
 # End of 11.0 tests
 #
+#
+# MDEV-29174: UPDATE of view that uses MERGE table
+#
+CREATE TABLE t1 (a int) ENGINE=MERGE;
+CREATE VIEW v1 AS SELECT a FROM t1;
+UPDATE v1 SET a=0;
+DROP VIEW v1;
+DROP TABLE t1;
+# End of 11.1 tests

mysql-test/main/merge.test

@@ -2859,10 +2859,6 @@ set global default_storage_engine=@save_default_storage_engine;
 # gone so execution of other tests won't be affected by their presence.
 --source include/wait_until_count_sessions.inc
 
---echo #
---echo # End of 10.0 tests
---echo #
-
 --echo #
 --echo # MDEV-27407 Different ASC/DESC index attributes on MERGE and underlying table can cause wrong results
 --echo #
@@ -2925,3 +2921,14 @@ DROP TABLE tm, t1, t2;
 --echo #
 --echo # End of 11.0 tests
 --echo #
+--echo #
+--echo # MDEV-29174: UPDATE of view that uses MERGE table
+--echo #
+
+CREATE TABLE t1 (a int) ENGINE=MERGE;
+CREATE VIEW v1 AS SELECT a FROM t1;
+UPDATE v1 SET a=0;
+DROP VIEW v1;
+DROP TABLE t1;
+
+--echo # End of 11.1 tests

sql/sql_base.cc

@@ -4765,7 +4765,6 @@ bool open_tables(THD *thd, const DDL_options_st &options,
     if (tbl->file->ha_table_flags() & HA_CAN_MULTISTEP_MERGE)
     {
       /* MERGE tables need to access parent and child TABLE_LISTs. */
-      DBUG_ASSERT(tbl->pos_in_table_list == tables);
       if (tbl->file->extra(HA_EXTRA_ATTACH_CHILDREN))
       {
         error= TRUE;