MDEV-21155 Assertion with versioned table upon DELETE from view of view after replacing first view

When view is merged by DT_MERGE_FOR_INSERT it is then skipped from
processing and doesn't update WHERE clause with
vers_setup_conds(). Note that view itself cannot work in
vers_setup_conds() because it doesn't have row_start, row_end
fields. Thus it is required to descend down to material TABLE_LIST
through calls of mysql_derived_prepare() and run vers_setup_conds()
from there. Luckily, all views (views of views, views of views of
views, etc.) are linked in one list through next_global pointer, so we
can skip all views of views and get straight to non-view TABLE_LIST by
checking its merge_underlying_list property for zero value (it is
assigned by DT_MERGE_FOR_INSERT for merged derived tables).

We have to do that only for UPDATE and DELETE. Other DML commands
don't use WHERE clause.

MDEV-21146 Assertion `m_lock_type == 2' in handler::ha_drop_table upon LOAD DATA

LOAD DATA does not use WHERE and the above call of vers_setup_conds()
is not needed. unit->prepare() led to wrongly locked temporary table.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/table.h b/sql/table.h
index ca5565250de..86e30034449 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -321,7 +321,7 @@ typedef struct st_grant_info
 
 enum tmp_table_type
 {
-  NO_TMP_TABLE, NON_TRANSACTIONAL_TMP_TABLE, TRANSACTIONAL_TMP_TABLE,
+  NO_TMP_TABLE= 0, NON_TRANSACTIONAL_TMP_TABLE, TRANSACTIONAL_TMP_TABLE,
   INTERNAL_TMP_TABLE, SYSTEM_TMP_TABLE
 };
 enum release_type { RELEASE_NORMAL, RELEASE_WAIT_FOR_DROP };