MDEV-35276 Assertion failure in find_producing_item upon a query from…

… a view

Two problem solved:

1) Item_default_value makes a shallow copy so the copy
 should not delete field belong to the Item

2) Item_default_value should not inherit
 derived_field_transformer_for_having and
 derived_field_transformer_for_where (in this variant
 pushing DEFAULT(f) is prohibited (return NULL) but
 if return "this" it will be allowed (should go with
 a lot of tests))

mysql-test/main/derived_cond_pushdown.result

@@ -19051,4 +19051,31 @@ EXPLAIN
   }
 }
 drop table t1, t2;
+#
+# MDEV-35276: Assertion failure in find_producing_item upon a query
+# from a view
+#
+# Note: for all followng queries with DEFAULT(f) hishdown is
+# prohibited
+CREATE VIEW v AS select 0 AS f;
+SELECT * FROM v WHERE f = DEFAULT(f);
+f
+0
+CREATE TABLE t1 (c int DEFAULT 0);
+insert into t1 values (0), (1);
+SELECT * FROM v,t1 WHERE f = DEFAULT(c);
+f	c
+0	0
+0	1
+ALTER TABLE t1 ALTER c SET DEFAULT 1;
+SELECT * FROM v,t1 WHERE f = DEFAULT(c);
+f	c
+drop table t1;
+create table t1 (a int, c int DEFAULT a);
+insert into t1 values (0, -1), (1, -2);
+SELECT * FROM v,t1 WHERE f = DEFAULT(c);
+f	a	c
+0	0	-1
+DROP VIEW v;
+DROP TABLE t1;
 # End of 10.5 tests

mysql-test/main/derived_cond_pushdown.test

@@ -4188,4 +4188,34 @@ execute stmt;
 
 drop table t1, t2;
 
+--echo #
+--echo # MDEV-35276: Assertion failure in find_producing_item upon a query
+--echo # from a view
+--echo #
+--echo # Note: for all followng queries with DEFAULT(f) hishdown is
+--echo # prohibited
+
+CREATE VIEW v AS select 0 AS f;
+
+SELECT * FROM v WHERE f = DEFAULT(f);
+
+CREATE TABLE t1 (c int DEFAULT 0);
+insert into t1 values (0), (1);
+
+SELECT * FROM v,t1 WHERE f = DEFAULT(c);
+
+ALTER TABLE t1 ALTER c SET DEFAULT 1;
+
+SELECT * FROM v,t1 WHERE f = DEFAULT(c);
+
+drop table t1;
+create table t1 (a int, c int DEFAULT a);
+insert into t1 values (0, -1), (1, -2);
+
+SELECT * FROM v,t1 WHERE f = DEFAULT(c);
+
+DROP VIEW v;
+DROP TABLE t1;
+
+
 --echo # End of 10.5 tests

sql/item.cc

@@ -9659,7 +9659,8 @@ bool Item_default_value::fix_fields(THD *thd, Item **items)
 
 void Item_default_value::cleanup()
 {
-  delete field;                        // Free cached blob data
+  if (!m_share_field)
+    delete field;                      // Free cached blob data
   Item_field::cleanup();
 }
 

sql/item.h

@@ -6646,16 +6646,21 @@ class Cached_item_field :public Cached_item
 
 class Item_default_value : public Item_field
 {
-  bool vcol_assignment_ok;
-  bool m_associated= false;
+  bool vcol_assignment_ok:1;
+  bool m_associated:1;
+  bool m_share_field:1;
 
   void calculate();
 public:
   Item *arg= nullptr;
   Item_default_value(THD *thd, Name_resolution_context *context_arg, Item *a,
                      bool vcol_assignment_arg)
     : Item_field(thd, context_arg),
-      vcol_assignment_ok(vcol_assignment_arg), arg(a) {}
+      vcol_assignment_ok(vcol_assignment_arg), arg(a)
+  {
+    m_associated= false;
+    m_share_field= false;
+  }
   Type type() const override { return DEFAULT_VALUE_ITEM; }
   bool eq(const Item *item, bool binary_cmp) const override;
   bool fix_fields(THD *, Item **) override;
@@ -6717,6 +6722,10 @@ class Item_default_value : public Item_field
 
   Item *transform(THD *thd, Item_transformer transformer, uchar *args)
     override;
+  Item *derived_field_transformer_for_having(THD *thd, uchar *arg) override
+  { return NULL; }
+  Item *derived_field_transformer_for_where(THD *thd, uchar *arg) override
+  { return NULL; }
   Field *create_tmp_field_ex(MEM_ROOT *root, TABLE *table, Tmp_field_src *src,
                              const Tmp_field_param *param) override;
 
@@ -6726,7 +6735,13 @@ class Item_default_value : public Item_field
   */
   bool associate_with_target_field(THD *thd, Item_field *field) override;
   Item *do_get_copy(THD *thd) const override
-  { return get_item_copy<Item_default_value>(thd, this); }
+  {
+    Item_default_value *new_item=
+      (Item_default_value *) get_item_copy<Item_default_value>(thd, this);
+    // This is a copy so do not manage the field and should not delete it
+    new_item->m_share_field= 1;
+    return new_item;
+  }
   Item* do_build_clone(THD *thd) const override { return get_copy(thd); }
 private:
   bool tie_field(THD *thd);