MDEV-16309 Split ::create_tmp_field() into virtual methods in Item

Detailed: changes:
1. Moving Field specific code into new methods on Field:
   - Field *Field::create_tmp_field(...)
   - virtual void init_for_tmp_table(...)

2. Removing virtual Item::create_tmp_field().
   Adding instead a new virtual method Item::create_tmp_field_ex().

   Note, a virtual create_tmp_field() still exists, but only for Item_sum.
   This resembles 10.0 code structure. Perhaps create_tmp_field() should
   be removed from Item_sum and Item_sum descendants should override
   create_tmp_field_ex() directly. This can be done in a separate commit.

3. Adding helper classes Tmp_field_src and Tmp_field_param,
   to make the API for Item::create_tmp_field_ex() smaller
   and easier to extend in the future.

4. Decomposing the public function create_tmp_field() into
   virtual implementations for Item and a number of its descendants:
   - Item_basic_value
   - Item_sp_variable
   - Item_name_const
   - Item_result_field
   - Item_field
   - Item_ref
   - Item_type_holder
   - Item_row
   - Item_func_sp
   - Item_func_user_var
   - Item_sum
   - Item_sum_field
   - Item_proc

5. Adding DBUG_ASSERT-only virtual implementations for
   Item types that should not appear in create_tmp_table_ex(),
   for easier debugging:
   - Item_nodeset_func
   - Item_nodeset_to_const_comparator
   - Item_null_result
   - Item_copy
   - Item_ident_for_show
   - Item_user_var_as_out_param

6. Moving public function create_tmp_field_from_field()
   as a method to Item_field.

7. Removing Item::set_result_field(). It's not needed any more.

8. Cleanup: Removing the enum value "EXPR_CACHE_ITEM",
   as it's not used for a very long time.

mysql-test/main/func_analyse.result

@@ -171,3 +171,48 @@ SELECT (SELECT 1 FROM t1 PROCEDURE ANALYSE()) FROM t2;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'PROCEDURE ANALYSE()) FROM t2' at line 1
 SELECT ((SELECT 1 FROM t1 PROCEDURE ANALYSE())) FROM t2;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'PROCEDURE ANALYSE())) FROM t2' at line 1
+#
+# Start of 10.4 tests
+#
+#
+# MDEV-16309 Split ::create_tmp_field() into virtual methods in Item
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+BEGIN NOT ATOMIC
+DECLARE rec ROW(Field_name TEXT,
+Min_value TEXT,
+Max_value TEXT,
+Min_length TEXT,
+Max_length TEXT,
+Empties_or_zeros TEXT,
+Nulls TEXT,
+Avg_value_or_avg_length TEXT,
+Std TEXT,
+Optimal_fieldtype TEXT);
+DECLARE c CURSOR FOR SELECT * FROM t1 PROCEDURE analyse();
+OPEN c;
+FETCH c INTO rec;
+CLOSE c;
+SELECT rec.field_name,
+rec.Min_value, rec.Max_value,
+rec.Min_length, rec. Max_length,
+rec.Empties_or_zeros, rec.Nulls,
+rec.Avg_value_or_avg_length, rec.Std,
+rec.Optimal_fieldtype;
+END;
+$$
+rec.field_name	test.t1.a
+rec.Min_value	1
+rec.Max_value	3
+rec.Min_length	1
+rec. Max_length	1
+rec.Empties_or_zeros	0
+rec.Nulls	0
+rec.Avg_value_or_avg_length	2.0000
+rec.Std	0.8165
+rec.Optimal_fieldtype	ENUM('1','2','3') NOT NULL
+DROP TABLE t1;
+#
+# End of 10.4 tests
+#

mysql-test/main/func_analyse.test

@@ -181,3 +181,47 @@ SELECT * FROM t1 NATURAL JOIN (SELECT * FROM t2 PROCEDURE ANALYSE());
 SELECT (SELECT 1 FROM t1 PROCEDURE ANALYSE()) FROM t2;
 --error ER_PARSE_ERROR
 SELECT ((SELECT 1 FROM t1 PROCEDURE ANALYSE())) FROM t2;
+
+
+--echo #
+--echo # Start of 10.4 tests
+--echo #
+
+--echo #
+--echo # MDEV-16309 Split ::create_tmp_field() into virtual methods in Item
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+--vertical_results
+DELIMITER $$;
+BEGIN NOT ATOMIC
+  DECLARE rec ROW(Field_name TEXT,
+                  Min_value TEXT,
+                  Max_value TEXT,
+                  Min_length TEXT,
+                  Max_length TEXT,
+                  Empties_or_zeros TEXT,
+                  Nulls TEXT,
+                  Avg_value_or_avg_length TEXT,
+                  Std TEXT,
+                  Optimal_fieldtype TEXT);
+  DECLARE c CURSOR FOR SELECT * FROM t1 PROCEDURE analyse();
+  OPEN c;
+  FETCH c INTO rec;
+  CLOSE c;
+  SELECT rec.field_name,
+         rec.Min_value, rec.Max_value,
+         rec.Min_length, rec. Max_length,
+         rec.Empties_or_zeros, rec.Nulls,
+         rec.Avg_value_or_avg_length, rec.Std,
+         rec.Optimal_fieldtype;
+END;
+$$
+DELIMITER ;$$
+--horizontal_results
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.4 tests
+--echo #

mysql-test/main/func_misc.result

@@ -1562,3 +1562,29 @@ Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is
 def					INET_ATON("255.255.255.255.255.255.255.255")	8	21	20	Y	32928	0	63
 INET_ATON("255.255.255.255.255.255.255.255")
 18446744073709551615
+#
+# End of 10.3 tests
+#
+#
+# Start of 10.4 tests
+#
+#
+# MDEV-16309 Split ::create_tmp_field() into virtual methods in Item
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+BEGIN NOT ATOMIC
+DECLARE a TEXT;
+DECLARE c CURSOR FOR SELECT NAME_CONST('x','y') FROM t1;
+OPEN c;
+FETCH c INTO a;
+CLOSE c;
+SELECT a;
+END;
+$$
+a
+y
+DROP TABLE t1;
+#
+# End of 10.4 tests
+#

mysql-test/main/func_misc.test

@@ -1203,3 +1203,34 @@ SELECT INET_ATON("255.255.255.255.255.255.255.255");
 
 --enable_ps_protocol
 --disable_metadata
+
+--echo #
+--echo # End of 10.3 tests
+--echo #
+
+--echo #
+--echo # Start of 10.4 tests
+--echo #
+
+--echo #
+--echo # MDEV-16309 Split ::create_tmp_field() into virtual methods in Item
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (1),(2),(3);
+DELIMITER $$;
+BEGIN NOT ATOMIC
+  DECLARE a TEXT;
+  DECLARE c CURSOR FOR SELECT NAME_CONST('x','y') FROM t1;
+  OPEN c;
+  FETCH c INTO a;
+  CLOSE c;
+  SELECT a;
+END;
+$$
+DELIMITER ;$$
+DROP TABLE t1;
+
+--echo #
+--echo # End of 10.4 tests
+--echo #

sql/field.cc

@@ -2331,6 +2331,36 @@ Field *Field::new_key_field(MEM_ROOT *root, TABLE *new_table,
 }
 
 
+/**
+  Create field for temporary table from given field.
+
+  @param thd	        Thread handler
+  @param table	        Temporary table
+  @param maybe_null_arg If the result field should be NULL-able,
+                        even if the original field is NOT NULL, e.g. for:
+                        - OUTER JOIN fields
+                        - WITH ROLLUP fields
+                        - arguments of aggregate functions, e.g. SUM(column1)
+  @retval               NULL, on error
+  @retval               pointer to the new field created, on success.
+*/
+
+Field *Field::create_tmp_field(MEM_ROOT *mem_root, TABLE *new_table,
+                               bool maybe_null_arg)
+{
+  Field *new_field;
+
+  if ((new_field= make_new_field(mem_root, new_table, new_table == table)))
+  {
+    new_field->init_for_tmp_table(this, new_table);
+    new_field->flags|= flags & NO_DEFAULT_VALUE_FLAG;
+    if (maybe_null_arg)
+      new_field->flags&= ~NOT_NULL_FLAG; // Because of outer join
+  }
+  return new_field;
+}
+
+
 /* This is used to generate a field in TABLE from TABLE_SHARE */
 
 Field *Field::clone(MEM_ROOT *root, TABLE *new_table)

sql/field.h

@@ -1228,6 +1228,12 @@ class Field: public Value_source
   virtual Field *new_key_field(MEM_ROOT *root, TABLE *new_table,
                                uchar *new_ptr, uint32 length,
                                uchar *new_null_ptr, uint new_null_bit);
+  Field *create_tmp_field(MEM_ROOT *root, TABLE *new_table,
+                          bool maybe_null_arg);
+  Field *create_tmp_field(MEM_ROOT *root, TABLE *new_table)
+  {
+    return create_tmp_field(root, new_table, maybe_null());
+  }
   Field *clone(MEM_ROOT *mem_root, TABLE *new_table);
   Field *clone(MEM_ROOT *mem_root, TABLE *new_table, my_ptrdiff_t diff,
                bool stat_flag= FALSE);
@@ -1388,7 +1394,19 @@ class Field: public Value_source
     orig_table= table= table_arg;
     set_table_name(&table_arg->alias);
   }
-
+  virtual void init_for_tmp_table(Field *org_field, TABLE *new_table)
+  {
+    init(new_table);
+    orig_table= org_field->orig_table;
+    vcol_info= 0;
+    cond_selectivity= 1.0;
+    next_equal_field= NULL;
+    option_list= NULL;
+    option_struct= NULL;
+    if (org_field->type() == MYSQL_TYPE_VAR_STRING ||
+        org_field->type() == MYSQL_TYPE_VARCHAR)
+      new_table->s->db_create_options|= HA_OPTION_PACK_RECORD;
+  }
   /* maximum possible display length */
   virtual uint32 max_display_length()= 0;
 
@@ -2307,6 +2325,11 @@ class Field_double :public Field_real {
       if (dec_arg >= FLOATING_POINT_DECIMALS)
         dec_arg= NOT_FIXED_DEC;
     }
+  void init_for_tmp_table(Field *org_field, TABLE *new_table)
+  {
+    Field::init_for_tmp_table(org_field, new_table);
+    not_fixed= true;
+  }
   const Type_handler *type_handler() const { return &type_handler_double; }
   enum ha_base_keytype key_type() const { return HA_KEYTYPE_DOUBLE; }
   int  store(const char *to,size_t length,CHARSET_INFO *charset);