MDEV-25576: The statement EXPLAIN running as regular statement and as prepared...

MDEV-25576: The statement EXPLAIN running as regular statement and as prepared statement produces different results for UPDATE with subquery

10.6 cleanup

sql/sql_base.cc

@@ -9276,21 +9276,6 @@ int dynamic_column_error_message(enum_dyncol_func_result rc)
   return rc;
 }
 
-
-/**
-  Turn on the SELECT_DESCRIBE flag for the primary SELECT_LEX of the statement
-  being processed in case the statement is EXPLAIN UPDATE/DELETE.
-
-  @param lex  current LEX
-*/
-
-void promote_select_describe_flag_if_needed(LEX *lex)
-{
-  if (lex->describe)
-    lex->first_select_lex()->options|= SELECT_DESCRIBE;
-}
-
-
 /**
   @} (end of group Data_Dictionary)
 */

sql/sql_base.h

@@ -518,8 +518,6 @@ bool extend_table_list(THD *thd, TABLE_LIST *tables,
                        Prelocking_strategy *prelocking_strategy,
                        bool has_prelocking_list);
 
-void promote_select_describe_flag_if_needed(LEX *lex);
-
 /**
   A context of open_tables() function, used to recover
   from a failed open_table() or open_routine() attempt.

sql/sql_delete.cc

@@ -366,7 +366,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   query_plan.select_lex= thd->lex->first_select_lex();
   query_plan.table= table;
 
-  promote_select_describe_flag_if_needed(thd->lex);
+  thd->lex->promote_select_describe_flag_if_needed();
 
   if (mysql_prepare_delete(thd, table_list, &conds, &delete_while_scanning))
     DBUG_RETURN(TRUE);

sql/sql_lex.h

@@ -4773,6 +4773,19 @@ struct LEX: public Query_tables_list
   bool resolve_references_to_cte(TABLE_LIST *tables,
                                  TABLE_LIST **tables_last);
 
+  /**
+    Turn on the SELECT_DESCRIBE flag for every SELECT_LEX involved into
+    the statement being processed in case the statement is EXPLAIN UPDATE/DELETE.
+
+    @param lex  current LEX
+  */
+
+  void promote_select_describe_flag_if_needed()
+  {
+    if (describe)
+      builtin_select.options |= SELECT_DESCRIBE;
+  }
+
 };
 
 

sql/sql_update.cc

@@ -468,7 +468,7 @@ int mysql_update(THD *thd,
   want_privilege= (table_list->view ? UPDATE_ACL :
                    table_list->grant.want_privilege);
 #endif
-  promote_select_describe_flag_if_needed(thd->lex);
+  thd->lex->promote_select_describe_flag_if_needed();
 
   if (mysql_prepare_update(thd, table_list, &conds, order_num, order))
     DBUG_RETURN(1);