fixed column number fetchinmg for subqueries. (BUG#8020)

fixed cols() method call (it have to be called only after fix_fields())


mysql-test/r/subselect.result:
  Comparison subquery with * and row
mysql-test/t/subselect.test:
  Comparison subquery with * and row
sql/item_cmpfunc.h:
  initialization allowed_arg_cols for autodetection
sql/item_func.cc:
  support of allowed_arg_cols autodetection by first argument
sql/item_func.h:
  commant
sql/item_subselect.cc:
  correct column number fetching for subqueries
sql/sql_lex.h:
  method to check that UNION is prepared

5 files changed, 31 insertions, 7 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 6834799688d..061ed468b78 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -213,7 +213,7 @@ class Item_bool_rowready_func2 :public Item_bool_func2
 public:
   Item_bool_rowready_func2(Item *a, Item *b) :Item_bool_func2(a, b)
   {
-    allowed_arg_cols= a->cols();
+    allowed_arg_cols= 0;  // Fetch this value from first argument
   }
   Item *neg_transformer(THD *thd);
   virtual Item *negated_item();
@@ -390,7 +390,10 @@ class Item_func_interval :public Item_int_func
   double *intervals;
 public:
   Item_func_interval(Item_row *a)
-    :Item_int_func(a),row(a),intervals(0) { allowed_arg_cols= a->cols(); }
+    :Item_int_func(a),row(a),intervals(0)
+  {
+    allowed_arg_cols= 0;    // Fetch this value from first argument
+  }
   longlong val_int();
   void fix_length_and_dec();
   const char *func_name() const { return "interval"; }
@@ -743,7 +746,7 @@ class Item_func_in :public Item_int_func
   Item_func_in(List<Item> &list)
     :Item_int_func(list), array(0), in_item(0), have_null(0)
   {
-    allowed_arg_cols= args[0]->cols();
+    allowed_arg_cols= 0;  // Fetch this value from first argument
   }
   longlong val_int();
   void fix_length_and_dec();
diff --git a/sql/item_func.cc b/sql/item_func.cc
index 7125f4704b8..bff49541252 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -303,10 +303,24 @@ Item_func::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 	We can't yet set item to *arg as fix_fields may change *arg
 	We shouldn't call fix_fields() twice, so check 'fixed' field first
       */
-      if ((!(*arg)->fixed && (*arg)->fix_fields(thd, tables, arg)) ||
-	  (*arg)->check_cols(allowed_arg_cols))
+      if ((!(*arg)->fixed && (*arg)->fix_fields(thd, tables, arg)))
 	return 1;				/* purecov: inspected */
+
       item= *arg;
+
+      if (allowed_arg_cols)
+      {
+        if (item->check_cols(allowed_arg_cols))
+          return 1;
+      }
+      else
+      {
+        /*  we have to fetch allowed_arg_cols from first argument */
+        DBUG_ASSERT(arg == args); // it is first argument
+        allowed_arg_cols= item->cols();
+        DBUG_ASSERT(allowed_arg_cols); // Can't be 0 any more
+      }
+
       if (item->maybe_null)
 	maybe_null=1;
 
diff --git a/sql/item_func.h b/sql/item_func.h
index ce2b34499d6..8a5347d675e 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -32,6 +32,10 @@ class Item_func :public Item_result_field
 {
 protected:
   Item **args, *tmp_arg[2];
+  /*
+    Allowed numbers of columns in result (usually 1, which means scalar value)
+    0 means get this number from first argument
+  */
   uint allowed_arg_cols;
 public:
   uint arg_count;
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 8516ea76a7e..2597427253c 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -1421,13 +1421,15 @@ int subselect_indexsubquery_engine::exec()
 
 uint subselect_single_select_engine::cols()
 {
-  return select_lex->item_list.elements;
+  DBUG_ASSERT(select_lex->join); // should be called after fix_fields()
+  return select_lex->join->fields_list.elements;
 }
 
 
 uint subselect_union_engine::cols()
 {
-  return unit->first_select()->item_list.elements;
+  DBUG_ASSERT(unit->is_prepared());  // should be called after fix_fields()
+  return unit->types.elements;
 }
 
 
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index e2e0bc61c23..7cb71607edf 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -371,6 +371,7 @@ public:
 
   ulong init_prepare_fake_select_lex(THD *thd);
   int change_result(select_subselect *result, select_subselect *old_result);
+  inline bool is_prepared() { return prepared; }
 
   friend void lex_start(THD *thd, uchar *buf, uint length);
   friend int subselect_union_engine::exec();