MDEV-24910 Crash with SELECT that uses table value constructor as a subselect

This bug caused crashes of the server when processing queries with table
value constructors (TVC) that contained subqueries and were used itself as
subselects. For such TVCs the following transformation is applied at the
prepare stage:
  VALUES (v1), ... (vn) => SELECT * FROM (VALUES (v1), ... (vn)) tvc_x.
This transformation allows to reduce the problem of evaluation of TVCs used
as subselects to the problem of evaluation of regular subselects.
The transformation is implemented in the wrap_tvc(). The code the function
to mimic the behaviour of the parser when processing the result of the
transformation. However this imitation was not free of some flaws. First
the function called the method exclude() that completely destroyed the
select tree structures below the transformed TVC. Second the function
used the procedure mysql_new_select to create st_select_lex nodes for
both wrapping select of the transformation and TVC. This also led to
constructing of invalid select tree structures.
The patch actually re-engineers the code of wrap_tvc().

Approved by Oleksandr Byelkin <sanja@mariadb.com>

1 files changed, 40 insertions, 27 deletions

diff --git a/sql/sql_tvc.cc b/sql/sql_tvc.cc
index 0a5f6687e17..0a771b592e4 100644
--- a/sql/sql_tvc.cc
+++ b/sql/sql_tvc.cc
@@ -654,44 +654,61 @@ st_select_lex *wrap_tvc(THD *thd, st_select_lex *tvc_sl,
 
   Query_arena backup;
   Query_arena *arena= thd->activate_stmt_arena_if_needed(&backup);
+
+  Item *item;
+  SELECT_LEX *wrapper_sl;
+  SELECT_LEX_UNIT *derived_unit;
+
   /*
-    Create SELECT_LEX of the select used in the result of transformation
+    Create SELECT_LEX wrapper_sl of the select used in the result
+    of the transformation
   */
-  lex->current_select= tvc_sl;
-  if (mysql_new_select(lex, 0, NULL))
+  if (!(wrapper_sl= new (thd->mem_root) SELECT_LEX()))
     goto err;
-  mysql_init_select(lex);
-  /* Create item list as '*' for the subquery SQ */
-  Item *item;
-  SELECT_LEX *wrapper_sl;
-  wrapper_sl= lex->current_select;
+  wrapper_sl->select_number= ++thd->lex->stmt_lex->current_select_number;
+  wrapper_sl->parent_lex= lex; /* Used in init_query. */
+  wrapper_sl->init_query();
+  wrapper_sl->init_select();
+
+  wrapper_sl->nest_level= tvc_sl->nest_level;
+  wrapper_sl->parsing_place= tvc_sl->parsing_place;
   wrapper_sl->linkage= tvc_sl->linkage;
-  wrapper_sl->parsing_place= SELECT_LIST;
+
+  lex->current_select= wrapper_sl;
   item= new (thd->mem_root) Item_field(thd, &wrapper_sl->context,
                                        NULL, NULL, &star_clex_str);
   if (item == NULL || add_item_to_list(thd, item))
     goto err;
   (wrapper_sl->with_wild)++;
-  
-  /* Exclude SELECT with TVC */
-  tvc_sl->exclude();
+
+  /* Include the newly created select into the global list of selects */
+  wrapper_sl->include_global((st_select_lex_node**)&lex->all_selects_list);
+
+  /* Substitute select node used of TVC for the newly created select */
+  tvc_sl->substitute_in_tree(wrapper_sl);
+
   /*
-    Create derived table DT that will wrap TVC in the result of transformation
+    Create a unit for the substituted select used for TVC and attach it
+    to the the wrapper select wrapper_sl as the only unit. The created
+    unit is the unit for the derived table tvc_x of the transformation.
   */
-  SELECT_LEX *tvc_select; // select for tvc
-  SELECT_LEX_UNIT *derived_unit; // unit for tvc_select
-  if (mysql_new_select(lex, 1, tvc_sl))
+  if (!(derived_unit= new (thd->mem_root) SELECT_LEX_UNIT()))
     goto err;
-  tvc_select= lex->current_select;
-  derived_unit= tvc_select->master_unit();
-  tvc_select->linkage= DERIVED_TABLE_TYPE;
+  derived_unit->init_query();
+  derived_unit->thd= thd;
+  derived_unit->include_down(wrapper_sl);
 
-  lex->current_select= wrapper_sl;
+  /*
+    Attach the select used of TVC as the only slave to the unit for
+    the derived table tvc_x of the transformation
+  */
+  derived_unit->add_slave(tvc_sl);
+  tvc_sl->linkage= DERIVED_TABLE_TYPE;
 
   /*
-    Create the name of the wrapping derived table and
-    add it to the FROM list of the wrapper
-   */
+    Generate the name of the derived table created for TVC and
+    add it to the FROM list of the wrapping select
+  */
   Table_ident *ti;
   LEX_CSTRING alias;
   TABLE_LIST *derived_tab;
@@ -710,10 +727,6 @@ st_select_lex *wrap_tvc(THD *thd, st_select_lex *tvc_sl,
   wrapper_sl->table_list.first->derived_type= DTYPE_TABLE | DTYPE_MATERIALIZE;
   lex->derived_tables|= DERIVED_SUBQUERY;
 
-  wrapper_sl->where= 0;
-  wrapper_sl->set_braces(false);
-  derived_unit->set_with_clause(0);
-
   if (arena)
     thd->restore_active_arena(arena, &backup);
   thd->lex->result= save_result;