MDEV-27937 Assertion failure when executing prepared statement with ? in IN list

This bug affected queries with IN predicates that contain parameter markers
in the value list. Such queries are executed via prepared statements.
The problem appeared only if the number of elements in the value list
was greater than the set value of the system variable
in_predicate_conversion_threshold.

The patch unconditionally prohibits conversion of an IN predicate to the
equivalent IN predicand if the value list of the IN predicate contains
parameters markers.

Approved by Oleksandr Byelkin <sanja@mariadb.com>

mysql-test/main/opt_tvc.result

@@ -732,3 +732,30 @@ a	b
 4	4
 drop table t1;
 SET @@in_predicate_conversion_threshold= default;
+#
+# MDEV-27937: Prepared statement with ? in the list if IN predicate
+#
+set in_predicate_conversion_threshold=2;
+create table t1 (id int, a int, b int);
+insert into t1 values (1,3,30), (2,7,70), (3,1,10);
+prepare stmt from "
+select * from t1 where a in (7, ?, 5, 1);
+";
+execute stmt using 3;
+id	a	b
+1	3	30
+2	7	70
+3	1	10
+deallocate prepare stmt;
+prepare stmt from "
+select * from t1 where (a,b) in ((7,70), (3,?), (5,50), (1,10));
+";
+execute stmt using 30;
+id	a	b
+1	3	30
+2	7	70
+3	1	10
+deallocate prepare stmt;
+drop table t1;
+set in_predicate_conversion_threshold=default;
+# End of 10.3 tests

mysql-test/main/opt_tvc.test

@@ -428,3 +428,29 @@ eval $query;
 drop table t1;
 SET @@in_predicate_conversion_threshold= default;
 
+--echo #
+--echo # MDEV-27937: Prepared statement with ? in the list if IN predicate
+--echo #
+
+set in_predicate_conversion_threshold=2;
+
+create table t1 (id int, a int, b int);
+insert into t1 values (1,3,30), (2,7,70), (3,1,10);
+
+prepare stmt from "
+select * from t1 where a in (7, ?, 5, 1);
+";
+execute stmt using 3;
+deallocate prepare stmt;
+
+prepare stmt from "
+select * from t1 where (a,b) in ((7,70), (3,?), (5,50), (1,10));
+";
+execute stmt using 30;
+deallocate prepare stmt;
+
+drop table t1;
+
+set in_predicate_conversion_threshold=default;
+
+--echo # End of 10.3 tests

sql/item_cmpfunc.cc

@@ -4472,10 +4472,11 @@ void Item_func_in::mark_as_condition_AND_part(TABLE_LIST *embedding)
   Query_arena *arena, backup;
   arena= thd->activate_stmt_arena_if_needed(&backup);
 
-  if (to_be_transformed_into_in_subq(thd))
+  if (!transform_into_subq_checked)
   {
-    transform_into_subq= true;
-    thd->lex->current_select->in_funcs.push_back(this, thd->mem_root);
+    if ((transform_into_subq= to_be_transformed_into_in_subq(thd)))
+      thd->lex->current_select->in_funcs.push_back(this, thd->mem_root);
+    transform_into_subq_checked= true;
   }
 
   if (arena)

sql/item_cmpfunc.h

@@ -2299,6 +2299,7 @@ class Item_func_in :public Item_func_opt_neg,
   SEL_TREE *get_func_mm_tree(RANGE_OPT_PARAM *param,
                              Field *field, Item *value);
   bool transform_into_subq;
+  bool transform_into_subq_checked;
 public:
   /// An array of values, created when the bisection lookup method is used
   in_vector *array;
@@ -2321,6 +2322,7 @@ class Item_func_in :public Item_func_opt_neg,
     Item_func_opt_neg(thd, list),
     Predicant_to_list_comparator(thd, arg_count - 1),
     transform_into_subq(false),
+    transform_into_subq_checked(false),
     array(0), have_null(0),
     arg_types_compatible(FALSE), emb_on_expr_nest(0)
   { }

sql/sql_tvc.cc

@@ -900,8 +900,6 @@ Item *Item_func_in::in_predicate_to_in_subs_transformer(THD *thd,
   if (!transform_into_subq)
     return this;
   
-  transform_into_subq= false;
-
   List<List_item> values;
 
   LEX *lex= thd->lex;
@@ -1058,15 +1056,38 @@ uint32 Item_func_in::max_length_of_left_expr()
 
 bool Item_func_in::to_be_transformed_into_in_subq(THD *thd)
 {
+  bool is_row_list= args[1]->type() == Item::ROW_ITEM;
   uint values_count= arg_count-1;
 
-  if (args[1]->type() == Item::ROW_ITEM)
+  if (is_row_list)
     values_count*= ((Item_row *)(args[1]))->cols();
 
   if (thd->variables.in_subquery_conversion_threshold == 0 ||
       thd->variables.in_subquery_conversion_threshold > values_count)
     return false;
 
+  if (!(thd->lex->context_analysis_only & CONTEXT_ANALYSIS_ONLY_PREPARE))
+    return true;
+
+  /* Occurence of '?' in IN list is checked only for PREPARE <stmt> commands */
+  for (uint i=1; i < arg_count; i++)
+  {
+    if (!is_row_list)
+    {
+      if (args[i]->type() == Item::PARAM_ITEM)
+        return false;
+    }
+    else
+    {
+      Item_row *row_list= (Item_row *)(args[i]);
+      for (uint j=0; j < row_list->cols(); j++)
+      {
+        if (row_list->element_index(j)->type() == Item::PARAM_ITEM)
+          return false;
+      }
+    }
+  }
+
   return true;
 }