MDEV-8910 Wrong metadata or field type for MAX(COALESCE(string_field))

mysql-test/r/func_hybrid_type.result

@@ -3059,5 +3059,177 @@ DROP TABLE t2;
 DROP TABLE t1;
 SET timestamp=DEFAULT;
 #
+# MDEV-8910 Wrong metadata or field type for MAX(COALESCE(string_field))
+#
+CREATE TABLE t1 (c1 TINYBLOB, c2 MEDIUMBLOB, c3 BLOB, c4 LONGBLOB);
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2,
+MAX(COALESCE(c3)) AS c3,
+MAX(COALESCE(c4)) AS c4
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varbinary(255) DEFAULT NULL,
+  `c2` mediumblob,
+  `c3` blob,
+  `c4` longblob
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2,
+MAX(COALESCE(c3)) AS c3,
+MAX(COALESCE(c4)) AS c4
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	255	0	Y	128	31	63
+def					c2	250	16777215	0	Y	128	31	63
+def					c3	252	65535	0	Y	128	31	63
+def					c4	251	4294967295	0	Y	128	31	63
+c1	c2	c3	c4
+NULL	NULL	NULL	NULL
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 CHAR(1), c2 CHAR(255)) CHARACTER SET latin1;
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varchar(1) DEFAULT NULL,
+  `c2` varchar(255) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	1	0	Y	0	31	8
+def					c2	253	255	0	Y	0	31	8
+c1	c2
+NULL	NULL
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 CHAR(1), c2 CHAR(255)) CHARACTER SET utf8;
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varchar(1) CHARACTER SET utf8 DEFAULT NULL,
+  `c2` varchar(255) CHARACTER SET utf8 DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	1	0	Y	0	31	8
+def					c2	253	255	0	Y	0	31	8
+c1	c2
+NULL	NULL
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 VARCHAR(1), c2 VARCHAR(255), c3 VARCHAR(20000)) CHARACTER SET latin1;
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2,
+MAX(COALESCE(c3)) AS c3
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varchar(1) DEFAULT NULL,
+  `c2` varchar(255) DEFAULT NULL,
+  `c3` text
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2,
+MAX(COALESCE(c3)) AS c3
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	1	0	Y	0	31	8
+def					c2	253	255	0	Y	0	31	8
+def					c3	252	20000	0	Y	0	31	8
+c1	c2	c3
+NULL	NULL	NULL
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 VARCHAR(1), c2 VARCHAR(255), c3 VARCHAR(20000)) CHARACTER SET utf8;
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2,
+MAX(COALESCE(c3)) AS c3
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varchar(1) CHARACTER SET utf8 DEFAULT NULL,
+  `c2` varchar(255) CHARACTER SET utf8 DEFAULT NULL,
+  `c3` text CHARACTER SET utf8
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1,
+MAX(COALESCE(c2)) AS c2,
+MAX(COALESCE(c3)) AS c3
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	1	0	Y	0	31	8
+def					c2	253	255	0	Y	0	31	8
+def					c3	252	60000	0	Y	0	31	8
+c1	c2	c3
+NULL	NULL	NULL
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 ENUM('a')) CHARACTER SET latin1;
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varchar(1) DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	1	0	Y	0	31	8
+c1
+NULL
+DROP TABLE t2;
+DROP TABLE t1;
+CREATE TABLE t1 (c1 ENUM('a')) CHARACTER SET utf8;
+CREATE TABLE t2 AS
+SELECT
+MAX(COALESCE(c1)) AS c1
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c1` varchar(1) CHARACTER SET utf8 DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+SELECT
+MAX(COALESCE(c1)) AS c1
+FROM t1;
+Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
+def					c1	253	1	0	Y	0	31	8
+c1
+NULL
+DROP TABLE t2;
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/func_hybrid_type.test

@@ -165,6 +165,140 @@ DROP TABLE t2;
 DROP TABLE t1;
 SET timestamp=DEFAULT;
 
+--echo #
+--echo # MDEV-8910 Wrong metadata or field type for MAX(COALESCE(string_field))
+--echo #
+CREATE TABLE t1 (c1 TINYBLOB, c2 MEDIUMBLOB, c3 BLOB, c4 LONGBLOB);
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2,
+  MAX(COALESCE(c3)) AS c3,
+  MAX(COALESCE(c4)) AS c4
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2,
+  MAX(COALESCE(c3)) AS c3,
+  MAX(COALESCE(c4)) AS c4
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1 (c1 CHAR(1), c2 CHAR(255)) CHARACTER SET latin1;
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1 (c1 CHAR(1), c2 CHAR(255)) CHARACTER SET utf8;
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1 (c1 VARCHAR(1), c2 VARCHAR(255), c3 VARCHAR(20000)) CHARACTER SET latin1;
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2,
+  MAX(COALESCE(c3)) AS c3
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2,
+  MAX(COALESCE(c3)) AS c3
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1 (c1 VARCHAR(1), c2 VARCHAR(255), c3 VARCHAR(20000)) CHARACTER SET utf8;
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2,
+  MAX(COALESCE(c3)) AS c3
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1,
+  MAX(COALESCE(c2)) AS c2,
+  MAX(COALESCE(c3)) AS c3
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1 (c1 ENUM('a')) CHARACTER SET latin1;
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+CREATE TABLE t1 (c1 ENUM('a')) CHARACTER SET utf8;
+CREATE TABLE t2 AS
+SELECT
+  MAX(COALESCE(c1)) AS c1
+FROM t1;
+SHOW CREATE TABLE t2;
+--disable_ps_protocol
+--enable_metadata
+SELECT
+  MAX(COALESCE(c1)) AS c1
+FROM t1;
+--disable_metadata
+--enable_ps_protocol
+DROP TABLE t2;
+DROP TABLE t1;
+
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item.cc

@@ -5362,17 +5362,6 @@ void Item::make_field(Send_field *tmp_field)
 }
 
 
-enum_field_types Item::string_field_type() const
-{
-  enum_field_types f_type= MYSQL_TYPE_VAR_STRING;
-  if (max_length >= 16777216)
-    f_type= MYSQL_TYPE_LONG_BLOB;
-  else if (max_length >= 65536)
-    f_type= MYSQL_TYPE_MEDIUM_BLOB;
-  return f_type;
-}
-
-
 void Item_empty_string::make_field(Send_field *tmp_field)
 {
   init_make_field(tmp_field, string_field_type());

sql/item.h

@@ -761,7 +761,10 @@ class Item: public Value_source,
   /* ... while cmp_type() specifies how it should be compared */
   Item_result cmp_type() const;
   virtual Item_result cast_to_int_type() const { return cmp_type(); }
-  virtual enum_field_types string_field_type() const;
+  enum_field_types string_field_type() const
+  {
+    return Type_handler::string_type_handler(max_length)->field_type();
+  }
   enum_field_types field_type() const;
   virtual enum Type type() const =0;
   /*

sql/item_sum.cc

@@ -1187,7 +1187,7 @@ Item_sum_hybrid::fix_fields(THD *thd, Item **ref)
   if ((!item->fixed && item->fix_fields(thd, args)) ||
       (item= args[0])->check_cols(1))
     return TRUE;
-  decimals=item->decimals;
+  Type_std_attributes::set(args[0]);
   with_subselect= args[0]->with_subselect;
 
   Item *item2= item->real_item();
@@ -1196,13 +1196,13 @@ Item_sum_hybrid::fix_fields(THD *thd, Item **ref)
   else if (item->cmp_type() == TIME_RESULT)
     set_handler_by_field_type(item2->field_type());
   else
-    set_handler_by_result_type(item2->result_type());
+    set_handler_by_result_type(item2->result_type(),
+                               max_length, collation.collation);
 
   switch (Item_sum_hybrid::result_type()) {
   case INT_RESULT:
   case DECIMAL_RESULT:
   case STRING_RESULT:
-    max_length= item->max_length;
     break;
   case REAL_RESULT:
     max_length= float_length(decimals);
@@ -1214,7 +1214,6 @@ Item_sum_hybrid::fix_fields(THD *thd, Item **ref)
   setup_hybrid(thd, args[0], NULL);
   /* MIN/MAX can return NULL for empty set indepedent of the used column */
   maybe_null= 1;
-  unsigned_flag=item->unsigned_flag;
   result_field=0;
   null_value=1;
   fix_length_and_dec();

sql/sql_type.cc

@@ -15,6 +15,7 @@
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
 #include "sql_type.h"
+#include "sql_const.h"
 
 static Type_handler_tiny        type_handler_tiny;
 static Type_handler_short       type_handler_short;
@@ -41,9 +42,47 @@ static Type_handler_blob        type_handler_blob;
 static Type_handler_geometry    type_handler_geometry;
 
 
-Type_handler_hybrid_field_type::Type_handler_hybrid_field_type()
-  :m_type_handler(&type_handler_double)
+/**
+  This method is used by:
+  - Item_func_set_user_var
+  - Item_func_get_user_var
+  - Item_user_var_as_out_param
+  - Item_func_udf_str
+
+  TODO: type_handler_adjusted_to_max_octet_length() and string_type_handler()
+  provide very similar functionality, to properly choose between
+  VARCHAR/VARBINARY vs TEXT/BLOB variations taking into accoung maximum
+  possible octet length.
+
+  We should probably get rid of either of them and use the same method
+  all around the code.
+*/
+const Type_handler *
+Type_handler::string_type_handler(uint max_octet_length) const
+{
+  if (max_octet_length >= 16777216)
+    return &type_handler_long_blob;
+  else if (max_octet_length >= 65536)
+    return &type_handler_medium_blob;
+  return &type_handler_varchar;
+}
+
+
+/**
+  This method is used by Item_sum_hybrid, e.g. MAX(item), MIN(item).
+*/
+const Type_handler *
+Type_handler_string_result::type_handler_adjusted_to_max_octet_length(
+                                                        uint max_octet_length,
+                                                        CHARSET_INFO *cs) const
 {
+  if (max_octet_length / cs->mbmaxlen <= CONVERT_IF_BIGGER_TO_BLOB)
+    return &type_handler_varchar; // See also Item::too_big_for_varchar()
+  if (max_octet_length >= 16777216)
+    return &type_handler_long_blob;
+  else if (max_octet_length >= 65536)
+    return &type_handler_medium_blob;
+  return &type_handler_blob;
 }
 
 
@@ -64,6 +103,12 @@ Type_handler_hybrid_field_type::get_handler_by_result_type(Item_result type)
 }
 
 
+Type_handler_hybrid_field_type::Type_handler_hybrid_field_type()
+  :m_type_handler(&type_handler_double)
+{
+}
+
+
 const Type_handler *
 Type_handler_hybrid_field_type::get_handler_by_field_type(enum_field_types type)
                                                           const

sql/sql_type.h

@@ -25,12 +25,19 @@
 
 class Type_handler
 {
+protected:
+  const Type_handler *string_type_handler(uint max_octet_length) const;
 public:
   virtual enum_field_types field_type() const= 0;
   virtual Item_result result_type() const= 0;
   virtual Item_result cmp_type() const= 0;
+  virtual const Type_handler*
+  type_handler_adjusted_to_max_octet_length(uint max_octet_length,
+                                            CHARSET_INFO *cs) const
+  { return this; }
 };
 
+
 /*** Abstract classes for every XXX_RESULT */
 
 class Type_handler_real_result: public Type_handler
@@ -70,6 +77,9 @@ class Type_handler_string_result: public Type_handler
 public:
   Item_result result_type() const { return STRING_RESULT; }
   Item_result cmp_type() const { return STRING_RESULT; }
+  const Type_handler *
+  type_handler_adjusted_to_max_octet_length(uint max_octet_length,
+                                            CHARSET_INFO *cs) const;
 };
 
 
@@ -283,10 +293,27 @@ class Type_handler_hybrid_field_type: public Type_handler
   {
     return (m_type_handler= get_handler_by_result_type(type));
   }
+  const Type_handler *set_handler_by_result_type(Item_result type,
+                                                 uint max_octet_length,
+                                                 CHARSET_INFO *cs)
+  {
+    m_type_handler= get_handler_by_result_type(type);
+    return m_type_handler=
+      m_type_handler->type_handler_adjusted_to_max_octet_length(max_octet_length,
+                                                                cs);
+  }
   const Type_handler *set_handler_by_field_type(enum_field_types type)
   {
     return (m_type_handler= get_handler_by_field_type(type));
   }
+  const Type_handler *
+  type_handler_adjusted_to_max_octet_length(uint max_octet_length,
+                                            CHARSET_INFO *cs) const
+  {
+    return
+      m_type_handler->type_handler_adjusted_to_max_octet_length(max_octet_length,
+                                                                cs);
+  }
 };
 
 #endif /* SQL_TYPE_H_INCLUDED */