MDEV-7487 Semi-join optimization for single-table update/delete statementsbb-10.10-mdev-7487

This patch allows to use semi-join optimization at the top level of
single-table update and delete statements.
The problem of supporting such optimization became easy to resolve after
processing a single-table update/delete statement started using JOIN
structure. This allowed to use JOIN::prepare() not only for multi-table
updates/deletes but for single-table ones as well. This was done in the
patch for mdev-28883:
 Re-design the upper level of handling UPDATE and DELETE statements.

Note that JOIN::prepare() detects all subqueries that can be considered
as candidates for semi-join optimization. The code added by this patch
looks for such candidates at the top level and if such candidates are found
in the processed single-table update/delete the statement is handled in
the same way as a multi-table update/delete.

Approved by Oleksandr Byelkin <sanja@mariadb.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/sql/sql_class.h b/sql/sql_class.h
index 167df5b07d9..3a2704ffe5f 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -7005,6 +7005,7 @@ public:
   // Methods used by ColumnStore
   uint get_num_of_tables() const { return num_of_tables; }
   TABLE_LIST* get_tables() const { return delete_tables; }
+  void set_delete_tables (TABLE_LIST *tbl) { delete_tables= tbl; }
 public:
   multi_delete(THD *thd_arg, TABLE_LIST *dt, uint num_of_tables);
   ~multi_delete();