A cleanup for `MDEV-20273 Add class Item_sum_min_max` - removing duplicate code

Reusing the MIN()/MAX() fix_length_and_dec() related code for window functions
- FIRST_VALUE()
- LAST_VALUE()
- NTH_VALUE()
- LEAD()
- LAG

6 files changed, 97 insertions, 109 deletions

diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 081db08e943..08ee190e96c 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -1184,11 +1184,73 @@ Item_sum_min_max::fix_fields(THD *thd, Item **ref)
 }
 
 
+bool Item_sum_hybrid::fix_length_and_dec_generic()
+{
+  Item *item= arguments()[0];
+  Type_std_attributes::set(item);
+  set_handler(item->type_handler());
+  return false;
+}
+
+
+/**
+  MAX/MIN for the traditional numeric types preserve the exact data type
+  from Fields, but do not preserve the exact type from Items:
+    MAX(float_field)              -> FLOAT
+    MAX(smallint_field)           -> LONGLONG
+    MAX(COALESCE(float_field))    -> DOUBLE
+    MAX(COALESCE(smallint_field)) -> LONGLONG
+  QQ: Items should probably be fixed to preserve the exact type.
+*/
+bool Item_sum_hybrid::fix_length_and_dec_numeric(const Type_handler *handler)
+{
+  Item *item= arguments()[0];
+  Item *item2= item->real_item();
+  Type_std_attributes::set(item);
+  if (item2->type() == Item::FIELD_ITEM)
+    set_handler(item2->type_handler());
+  else
+    set_handler(handler);
+  return false;
+}
+
+
+/**
+   MAX(str_field) converts ENUM/SET to CHAR, and preserve all other types
+   for Fields.
+   QQ: This works differently from UNION, which preserve the exact data
+   type for ENUM/SET if the joined ENUM/SET fields are equally defined.
+   Perhaps should be fixed.
+   MAX(str_item) chooses the best suitable string type.
+*/
+bool Item_sum_hybrid::fix_length_and_dec_string()
+{
+  Item *item= arguments()[0];
+  Item *item2= item->real_item();
+  Type_std_attributes::set(item);
+  if (item2->type() == Item::FIELD_ITEM)
+  {
+    // Fields: convert ENUM/SET to CHAR, preserve the type otherwise.
+    set_handler(item->type_handler());
+  }
+  else
+  {
+    // Items: choose VARCHAR/BLOB/MEDIUMBLOB/LONGBLOB, depending on length.
+    set_handler(type_handler_varchar.
+          type_handler_adjusted_to_max_octet_length(max_length,
+                                                    collation.collation));
+  }
+  return false;
+}
+
+
 bool Item_sum_min_max::fix_length_and_dec()
 {
   DBUG_ASSERT(args[0]->field_type() == args[0]->real_item()->field_type());
   DBUG_ASSERT(args[0]->result_type() == args[0]->real_item()->result_type());
-  return args[0]->type_handler()->Item_sum_min_max_fix_length_and_dec(this);
+  /* MIN/MAX can return NULL for empty set indepedent of the used column */
+  maybe_null= null_value= true;
+  return args[0]->type_handler()->Item_sum_hybrid_fix_length_and_dec(this);
 }
 
 
diff --git a/sql/item_sum.h b/sql/item_sum.h
index df37d0dbfa4..a3e10c25763 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -1044,6 +1044,9 @@ public:
   { }
   const Type_handler *type_handler() const
   { return Type_handler_hybrid_field_type::type_handler(); }
+  bool fix_length_and_dec_generic();
+  bool fix_length_and_dec_numeric(const Type_handler *h);
+  bool fix_length_and_dec_string();
 };
 
 
diff --git a/sql/item_windowfunc.cc b/sql/item_windowfunc.cc
index 98474f62d4f..17c5740feda 100644
--- a/sql/item_windowfunc.cc
+++ b/sql/item_windowfunc.cc
@@ -353,39 +353,15 @@ bool Item_sum_hybrid_simple::fix_fields(THD *thd, Item **ref)
     if (args[i]->fix_fields_if_needed_for_scalar(thd, &args[i]))
       return TRUE;
   }
-  Type_std_attributes::set(args[0]);
+
   for (uint i= 0; i < arg_count && !m_with_subquery; i++)
     m_with_subquery|= args[i]->with_subquery();
 
-  Item *item2= args[0]->real_item();
-  if (item2->type() == Item::FIELD_ITEM)
-    set_handler(item2->type_handler());
-  else if (args[0]->cmp_type() == TIME_RESULT)
-    set_handler(item2->type_handler());
-  else
-    set_handler_by_result_type(item2->result_type(),
-                               max_length, collation.collation);
+  if (fix_length_and_dec())
+    return true;
 
-  switch (result_type()) {
-  case INT_RESULT:
-  case DECIMAL_RESULT:
-  case STRING_RESULT:
-    break;
-  case REAL_RESULT:
-    max_length= float_length(decimals);
-    break;
-  case ROW_RESULT:
-  case TIME_RESULT:
-    DBUG_ASSERT(0); // XXX(cvicentiu) Should this never happen?
-    return TRUE;
-  };
   setup_hybrid(thd, args[0]);
-  /* MIN/MAX can return NULL for empty set indepedent of the used column */
-  maybe_null= 1;
   result_field=0;
-  null_value=1;
-  if (fix_length_and_dec())
-    return TRUE;
 
   if (check_sum_func(thd, ref))
     return TRUE;
@@ -397,6 +373,14 @@ bool Item_sum_hybrid_simple::fix_fields(THD *thd, Item **ref)
   return FALSE;
 }
 
+
+bool Item_sum_hybrid_simple::fix_length_and_dec()
+{
+  maybe_null= null_value= true;
+  return args[0]->type_handler()->Item_sum_hybrid_fix_length_and_dec(this);
+}
+
+
 bool Item_sum_hybrid_simple::add()
 {
   value->store(args[0]);
diff --git a/sql/item_windowfunc.h b/sql/item_windowfunc.h
index 1432643dfc8..e6389c01832 100644
--- a/sql/item_windowfunc.h
+++ b/sql/item_windowfunc.h
@@ -307,6 +307,7 @@ class Item_sum_hybrid_simple : public Item_sum_hybrid
 
   bool add();
   bool fix_fields(THD *, Item **);
+  bool fix_length_and_dec();
   void setup_hybrid(THD *thd, Item *item);
   double val_real();
   longlong val_int();
diff --git a/sql/sql_type.cc b/sql/sql_type.cc
index 573d9721fc1..114e4cac367 100644
--- a/sql/sql_type.cc
+++ b/sql/sql_type.cc
@@ -365,7 +365,7 @@ Type_handler::blob_type_handler(const Item *item)
 
 /**
   This method is used by:
-  - Item_sum_min_max, e.g. MAX(item), MIN(item).
+  - Item_sum_hybrid, e.g. MAX(item), MIN(item).
   - Item_func_set_user_var
 */
 const Type_handler *
@@ -3076,87 +3076,33 @@ bool Type_handler_real_result::
 
 /*************************************************************************/
 
-/**
-  MAX/MIN for the traditional numeric types preserve the exact data type
-  from Fields, but do not preserve the exact type from Items:
-    MAX(float_field)              -> FLOAT
-    MAX(smallint_field)           -> LONGLONG
-    MAX(COALESCE(float_field))    -> DOUBLE
-    MAX(COALESCE(smallint_field)) -> LONGLONG
-  QQ: Items should probably be fixed to preserve the exact type.
-*/
-bool Type_handler_numeric::
-       Item_sum_min_max_fix_length_and_dec_numeric(Item_sum_min_max *func,
-                                                   const Type_handler *handler)
-                                                   const
-{
-  Item *item= func->arguments()[0];
-  Item *item2= item->real_item();
-  func->Type_std_attributes::set(item);
-  /* MIN/MAX can return NULL for empty set indepedent of the used column */
-  func->maybe_null= func->null_value= true;
-  if (item2->type() == Item::FIELD_ITEM)
-    func->set_handler(item2->type_handler());
-  else
-    func->set_handler(handler);
-  return false;
-}
-
-
 bool Type_handler_int_result::
-       Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const
+       Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const
 {
-  return Item_sum_min_max_fix_length_and_dec_numeric(func,
-                                                     &type_handler_longlong);
+  return func->fix_length_and_dec_numeric(&type_handler_longlong);
 }
 
 
 bool Type_handler_real_result::
-       Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const
+       Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const
 {
-  (void) Item_sum_min_max_fix_length_and_dec_numeric(func,
-                                                     &type_handler_double);
+  (void) func->fix_length_and_dec_numeric(&type_handler_double);
   func->max_length= func->float_length(func->decimals);
   return false;
 }
 
 
 bool Type_handler_decimal_result::
-       Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const
+       Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const
 {
-  return Item_sum_min_max_fix_length_and_dec_numeric(func,
-                                                     &type_handler_newdecimal);
+  return func->fix_length_and_dec_numeric(&type_handler_newdecimal);
 }
 
 
-/**
-   MAX(str_field) converts ENUM/SET to CHAR, and preserve all other types
-   for Fields.
-   QQ: This works differently from UNION, which preserve the exact data
-   type for ENUM/SET if the joined ENUM/SET fields are equally defined.
-   Perhaps should be fixed.
-   MAX(str_item) chooses the best suitable string type.
-*/
 bool Type_handler_string_result::
-       Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const
+       Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const
 {
-  Item *item= func->arguments()[0];
-  Item *item2= item->real_item();
-  func->Type_std_attributes::set(item);
-  func->maybe_null= func->null_value= true;
-  if (item2->type() == Item::FIELD_ITEM)
-  {
-    // Fields: convert ENUM/SET to CHAR, preserve the type otherwise.
-    func->set_handler(item->type_handler());
-  }
-  else
-  {
-    // Items: choose VARCHAR/BLOB/MEDIUMBLOB/LONGBLOB, depending on length.
-    func->set_handler(type_handler_varchar.
-          type_handler_adjusted_to_max_octet_length(func->max_length,
-                                                    func->collation.collation));
-  }
-  return false;
+  return func->fix_length_and_dec_string();
 }
 
 
@@ -3164,13 +3110,9 @@ bool Type_handler_string_result::
   Traditional temporal types always preserve the type of the argument.
 */
 bool Type_handler_temporal_result::
-       Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const
+       Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const
 {
-  Item *item= func->arguments()[0];
-  func->Type_std_attributes::set(item);
-  func->maybe_null= func->null_value= true;
-  func->set_handler(item->type_handler());
-  return false;
+  return func->fix_length_and_dec_generic();
 }
 
 
diff --git a/sql/sql_type.h b/sql/sql_type.h
index a7915ddc463..df4b99569c1 100644
--- a/sql/sql_type.h
+++ b/sql/sql_type.h
@@ -33,7 +33,7 @@ class Item;
 class Item_param;
 class Item_cache;
 class Item_func_or_sum;
-class Item_sum_min_max;
+class Item_sum_hybrid;
 class Item_sum_sum;
 class Item_sum_avg;
 class Item_sum_variance;
@@ -1314,7 +1314,7 @@ public:
                                                 Item_func_min_max *func,
                                                 Item **items,
                                                 uint nitems) const;
-  virtual bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *) const= 0;
+  virtual bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *) const= 0;
   virtual bool Item_sum_sum_fix_length_and_dec(Item_sum_sum *) const= 0;
   virtual bool Item_sum_avg_fix_length_and_dec(Item_sum_avg *) const= 0;
   virtual
@@ -1563,7 +1563,7 @@ public:
     DBUG_ASSERT(0);
     return true;
   }
-  bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const
+  bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const
   {
     DBUG_ASSERT(0);
     return true;
@@ -1742,10 +1742,6 @@ public:
 */
 class Type_handler_numeric: public Type_handler
 {
-protected:
-  bool Item_sum_min_max_fix_length_and_dec_numeric(Item_sum_min_max *func,
-                                                   const Type_handler *handler)
-                                                   const;
 public:
   String *print_item_value(THD *thd, Item *item, String *str) const;
   double Item_func_min_max_val_real(Item_func_min_max *) const;
@@ -1796,7 +1792,7 @@ public:
                                        Item **items, uint nitems) const;
   bool Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
                                         Item **items, uint nitems) const;
-  bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const;
+  bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const;
   bool Item_sum_sum_fix_length_and_dec(Item_sum_sum *) const;
   bool Item_sum_avg_fix_length_and_dec(Item_sum_avg *) const;
   bool Item_sum_variance_fix_length_and_dec(Item_sum_variance *) const;
@@ -1874,7 +1870,7 @@ public:
                                        Type_handler_hybrid_field_type *,
                                        Type_all_attributes *atrr,
                                        Item **items, uint nitems) const;
-  bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const;
+  bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const;
   bool Item_sum_sum_fix_length_and_dec(Item_sum_sum *) const;
   bool Item_sum_avg_fix_length_and_dec(Item_sum_avg *) const;
   bool Item_sum_variance_fix_length_and_dec(Item_sum_variance *) const;
@@ -2068,7 +2064,7 @@ public:
                                        Type_handler_hybrid_field_type *,
                                        Type_all_attributes *atrr,
                                        Item **items, uint nitems) const;
-  bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const;
+  bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const;
   bool Item_sum_sum_fix_length_and_dec(Item_sum_sum *) const;
   bool Item_sum_avg_fix_length_and_dec(Item_sum_avg *) const;
   bool Item_sum_variance_fix_length_and_dec(Item_sum_variance *) const;
@@ -2145,7 +2141,7 @@ public:
                                             const Item *outer) const;
   bool Item_func_min_max_fix_attributes(THD *thd, Item_func_min_max *func,
                                         Item **items, uint nitems) const;
-  bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const;
+  bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const;
   bool Item_sum_sum_fix_length_and_dec(Item_sum_sum *) const;
   bool Item_sum_avg_fix_length_and_dec(Item_sum_avg *) const;
   bool Item_sum_variance_fix_length_and_dec(Item_sum_variance *) const;
@@ -2258,7 +2254,7 @@ public:
                                        Type_handler_hybrid_field_type *,
                                        Type_all_attributes *atrr,
                                        Item **items, uint nitems) const;
-  bool Item_sum_min_max_fix_length_and_dec(Item_sum_min_max *func) const;
+  bool Item_sum_hybrid_fix_length_and_dec(Item_sum_hybrid *func) const;
   bool Item_sum_sum_fix_length_and_dec(Item_sum_sum *) const;
   bool Item_sum_avg_fix_length_and_dec(Item_sum_avg *) const;
   bool Item_sum_variance_fix_length_and_dec(Item_sum_variance *) const;