MDEV-10342 Providing compatibility for basic SQL built-in functions

Adding functions NVL() and NVL2().

mysql-test/suite/compat/oracle/r/func_case.result

+SET sql_mode=ORACLE;
+SELECT NVL(NULL, 'a'), NVL('a', 'b');
+NVL(NULL, 'a')	NVL('a', 'b')
+a	a
+SELECT NVL2(NULL, 'a', 'b'), NVL2('a', 'b', 'c');
+NVL2(NULL, 'a', 'b')	NVL2('a', 'b', 'c')
+b	b

mysql-test/suite/compat/oracle/t/func_case.test

+#
+# Testing CASE and its abbreviations
+#
+
+SET sql_mode=ORACLE;
+
+SELECT NVL(NULL, 'a'), NVL('a', 'b');
+
+SELECT NVL2(NULL, 'a', 'b'), NVL2('a', 'b', 'c');

sql/item.h

@@ -543,6 +543,47 @@ class Item: public Value_source,
 
   void push_note_converted_to_negative_complement(THD *thd);
   void push_note_converted_to_positive_complement(THD *thd);
+
+  /* Helper methods, to get an Item value from another Item */
+  double val_real_from_item(Item *item)
+  {
+    DBUG_ASSERT(fixed == 1);
+    double value= item->val_real();
+    null_value= item->null_value;
+    return value;
+  }
+  longlong val_int_from_item(Item *item)
+  {
+    DBUG_ASSERT(fixed == 1);
+    longlong value= item->val_int();
+    null_value= item->null_value;
+    return value;
+  }
+  String *val_str_from_item(Item *item, String *str)
+  {
+    DBUG_ASSERT(fixed == 1);
+    String *res= item->val_str(str);
+    if (res)
+      res->set_charset(collation.collation);
+    if ((null_value= item->null_value))
+      res= NULL;
+    return res;
+  }
+  my_decimal *val_decimal_from_item(Item *item, my_decimal *decimal_value)
+  {
+    DBUG_ASSERT(fixed == 1);
+    my_decimal *value= item->val_decimal(decimal_value);
+    if ((null_value= item->null_value))
+      value= NULL;
+    return value;
+  }
+  bool get_date_with_conversion_from_item(Item *item,
+                                          MYSQL_TIME *ltime, uint fuzzydate)
+  {
+    DBUG_ASSERT(fixed == 1);
+    return (null_value= item->get_date_with_conversion(ltime, fuzzydate));
+  }
+
 public:
   /*
     Cache val_str() into the own buffer, e.g. to evaluate constant

sql/item_cmpfunc.cc

@@ -2365,91 +2365,6 @@ void Item_func_if::fix_after_pullout(st_select_lex *new_parent, Item **ref)
 }
 
 
-void Item_func_if::cache_type_info(Item *source)
-{
-  Type_std_attributes::set(source);
-  set_handler_by_field_type(source->field_type());
-  maybe_null=         source->maybe_null;
-}
-
-
-void
-Item_func_if::fix_length_and_dec()
-{
-  // Let IF(cond, expr, NULL) and IF(cond, NULL, expr) inherit type from expr.
-  if (args[1]->type() == NULL_ITEM)
-  {
-    cache_type_info(args[2]);
-    maybe_null= true;
-    // If both arguments are NULL, make resulting type BINARY(0).
-    if (args[2]->type() == NULL_ITEM)
-      set_handler_by_field_type(MYSQL_TYPE_STRING);
-    return;
-  }
-  if (args[2]->type() == NULL_ITEM)
-  {
-    cache_type_info(args[1]);
-    maybe_null= true;
-    return;
-  }
-  Item_func_case_abbreviation2::fix_length_and_dec2(args + 1);
-}
-
-
-double
-Item_func_if::real_op()
-{
-  DBUG_ASSERT(fixed == 1);
-  Item *arg= args[0]->val_bool() ? args[1] : args[2];
-  double value= arg->val_real();
-  null_value=arg->null_value;
-  return value;
-}
-
-longlong
-Item_func_if::int_op()
-{
-  DBUG_ASSERT(fixed == 1);
-  Item *arg= args[0]->val_bool() ? args[1] : args[2];
-  longlong value=arg->val_int();
-  null_value=arg->null_value;
-  return value;
-}
-
-String *
-Item_func_if::str_op(String *str)
-{
-  DBUG_ASSERT(fixed == 1);
-  Item *arg= args[0]->val_bool() ? args[1] : args[2];
-  String *res=arg->val_str(str);
-  if (res)
-    res->set_charset(collation.collation);
-  if ((null_value=arg->null_value))
-    res= NULL;
-  return res;
-}
-
-
-my_decimal *
-Item_func_if::decimal_op(my_decimal *decimal_value)
-{
-  DBUG_ASSERT(fixed == 1);
-  Item *arg= args[0]->val_bool() ? args[1] : args[2];
-  my_decimal *value= arg->val_decimal(decimal_value);
-  if ((null_value= arg->null_value))
-    value= NULL;
-  return value;
-}
-
-
-bool Item_func_if::date_op(MYSQL_TIME *ltime, uint fuzzydate)
-{
-  DBUG_ASSERT(fixed == 1);
-  Item *arg= args[0]->val_bool() ? args[1] : args[2];
-  return (null_value= arg->get_date_with_conversion(ltime, fuzzydate));
-}
-
-
 void Item_func_nullif::split_sum_func(THD *thd, Ref_ptr_array ref_pointer_array,
                                       List<Item> &fields, uint flags)
 {

sql/item_cmpfunc.h

@@ -993,6 +993,7 @@ class Item_func_coalesce :public Item_func_hybrid_field_type
   Case abbreviations that aggregate its result field type by two arguments:
     IFNULL(arg1, arg2)
     IF(switch, arg1, arg2)
+    NVL2(switch, arg1, arg2)
 */
 class Item_func_case_abbreviation2 :public Item_func_hybrid_field_type
 {
@@ -1003,6 +1004,34 @@ class Item_func_case_abbreviation2 :public Item_func_hybrid_field_type
       fix_attributes(items, 2);
   }
   uint decimal_precision2(Item **args) const;
+
+  void cache_type_info(const Item *source, bool maybe_null_arg)
+  {
+    Type_std_attributes::set(source);
+    set_handler_by_field_type(source->field_type());
+    maybe_null= maybe_null_arg;
+  }
+
+  void fix_length_and_dec2_eliminate_null(Item **items)
+  {
+    // Let IF(cond, expr, NULL) and IF(cond, NULL, expr) inherit type from expr.
+    if (items[0]->type() == NULL_ITEM)
+    {
+      cache_type_info(items[1], true);
+      // If both arguments are NULL, make resulting type BINARY(0).
+      if (items[1]->type() == NULL_ITEM)
+        set_handler_by_field_type(MYSQL_TYPE_STRING);
+    }
+    else if (items[1]->type() == NULL_ITEM)
+    {
+      cache_type_info(items[0], true);
+    }
+    else
+    {
+      fix_length_and_dec2(items);
+    }
+  }
+
 public:
   Item_func_case_abbreviation2(THD *thd, Item *a, Item *b):
     Item_func_hybrid_field_type(thd, a, b) { }
@@ -1040,19 +1069,61 @@ class Item_func_ifnull :public Item_func_case_abbreviation2
 };
 
 
-class Item_func_if :public Item_func_case_abbreviation2
+/**
+  Case abbreviations that have a switch argument and
+  two return arguments to choose from. Returns the value
+  of either of the two return arguments depending on the switch argument value.
+
+  IF(switch, arg1, arg2)
+  NVL(switch, arg1, arg2)
+*/
+class Item_func_case_abbreviation2_switch: public Item_func_case_abbreviation2
+{
+protected:
+  virtual Item *find_item() const= 0;
+
+public:
+  Item_func_case_abbreviation2_switch(THD *thd, Item *a, Item *b, Item *c)
+    :Item_func_case_abbreviation2(thd, a, b, c)
+  { }
+
+  bool date_op(MYSQL_TIME *ltime, uint fuzzydate)
+  {
+    return get_date_with_conversion_from_item(find_item(), ltime, fuzzydate);
+  }
+  longlong int_op()
+  {
+    return val_int_from_item(find_item());
+  }
+  double real_op()
+  {
+    return val_real_from_item(find_item());
+  }
+  my_decimal *decimal_op(my_decimal *decimal_value)
+  {
+    return val_decimal_from_item(find_item(), decimal_value);
+  }
+  String *str_op(String *str)
+  {
+    return val_str_from_item(find_item(), str);
+  }
+};
+
+
+class Item_func_if :public Item_func_case_abbreviation2_switch
 {
+protected:
+  Item *find_item() const { return args[0]->val_bool() ? args[1] : args[2]; }
+
 public:
   Item_func_if(THD *thd, Item *a, Item *b, Item *c):
-    Item_func_case_abbreviation2(thd, a, b, c)
+    Item_func_case_abbreviation2_switch(thd, a, b, c)
   {}
-  bool date_op(MYSQL_TIME *ltime, uint fuzzydate);
-  longlong int_op();
-  double real_op();
-  my_decimal *decimal_op(my_decimal *);
-  String *str_op(String *);
   bool fix_fields(THD *, Item **);
-  void fix_length_and_dec();
+  void fix_length_and_dec()
+  {
+    fix_length_and_dec2_eliminate_null(args + 1);
+  }
   uint decimal_precision() const
   {
     return Item_func_case_abbreviation2::decimal_precision2(args + 1);
@@ -1067,6 +1138,29 @@ class Item_func_if :public Item_func_case_abbreviation2
 };
 
 
+class Item_func_nvl2 :public Item_func_case_abbreviation2_switch
+{
+protected:
+  Item *find_item() const { return args[0]->is_null() ? args[2] : args[1]; }
+
+public:
+  Item_func_nvl2(THD *thd, Item *a, Item *b, Item *c):
+    Item_func_case_abbreviation2_switch(thd, a, b, c)
+  {}
+  const char *func_name() const { return "nvl2"; }
+  void fix_length_and_dec()
+  {
+    fix_length_and_dec2_eliminate_null(args + 1);
+  }
+  uint decimal_precision() const
+  {
+    return Item_func_case_abbreviation2::decimal_precision2(args + 1);
+  }
+  Item *get_copy(THD *thd, MEM_ROOT *mem_root)
+  { return get_item_copy<Item_func_nvl2>(thd, mem_root, this); }
+};
+
+
 class Item_func_nullif :public Item_func_hybrid_field_type
 {
   Arg_comparator cmp;

sql/item_create.cc

@@ -711,6 +711,19 @@ class Create_func_contains : public Create_func_arg2
 #endif
 
 
+class Create_func_nvl2 : public Create_func_arg3
+{
+public:
+  virtual Item *create_3_arg(THD *thd, Item *arg1, Item *arg2, Item *arg3);
+
+  static Create_func_nvl2 s_singleton;
+
+protected:
+  Create_func_nvl2() {}
+  virtual ~Create_func_nvl2() {}
+};
+
+
 class Create_func_conv : public Create_func_arg3
 {
 public:
@@ -3931,6 +3944,15 @@ Create_func_contains::create_2_arg(THD *thd, Item *arg1, Item *arg2)
 #endif
 
 
+Create_func_nvl2 Create_func_nvl2::s_singleton;
+
+Item*
+Create_func_nvl2::create_3_arg(THD *thd, Item *arg1, Item *arg2, Item *arg3)
+{
+  return new (thd->mem_root) Item_func_nvl2(thd, arg1, arg2, arg3);
+}
+
+
 Create_func_conv Create_func_conv::s_singleton;
 
 Item*
@@ -6884,6 +6906,8 @@ static Native_func_registry func_array[] =
   { { C_STRING_WITH_LEN("MULTIPOLYGONFROMTEXT") }, GEOM_BUILDER(Create_func_geometry_from_text)},
   { { C_STRING_WITH_LEN("MULTIPOLYGONFROMWKB") }, GEOM_BUILDER(Create_func_geometry_from_wkb)},
   { { C_STRING_WITH_LEN("NAME_CONST") }, BUILDER(Create_func_name_const)},
+  { { C_STRING_WITH_LEN("NVL") }, BUILDER(Create_func_ifnull)},
+  { { C_STRING_WITH_LEN("NVL2") }, BUILDER(Create_func_nvl2)},
   { { C_STRING_WITH_LEN("NULLIF") }, BUILDER(Create_func_nullif)},
   { { C_STRING_WITH_LEN("NUMGEOMETRIES") }, GEOM_BUILDER(Create_func_numgeometries)},
   { { C_STRING_WITH_LEN("NUMINTERIORRINGS") }, GEOM_BUILDER(Create_func_numinteriorring)},