BUG#14139: When handling "CREATE TABLE(field_X type_spec,...) SELECT smth AS field_X, ...."

avoid multiplying length of field_X by charset->mbmaxlen twice when calculating space 
required for field_X in the new table.

mysql-test/r/create.result

@@ -621,3 +621,14 @@ create table if not exists t1 (a int);
 Warnings:
 Note	1050	Table 't1' already exists
 drop table t1;
+create table t1 (
+a varchar(112) charset utf8 collate utf8_bin not null,
+primary key (a)
+) select 'test' as a ;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` varchar(112) character set utf8 collate utf8_bin NOT NULL default '',
+  PRIMARY KEY  (`a`)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;

mysql-test/t/create.test

@@ -526,4 +526,12 @@ create table t1 (a int);
 create table if not exists t1 (a int);
 drop table t1;
 
+# BUG#14139
+create table t1 (
+  a varchar(112) charset utf8 collate utf8_bin not null,
+  primary key (a)
+) select 'test' as a ;
+show create table t1;
+drop table t1;
+
 # End of 4.1 tests

sql/field.cc

@@ -6511,8 +6511,20 @@ bool Field_num::eq_def(Field *field)
 ** Handling of field and create_field
 *****************************************************************************/
 
+/*
+  Convert create_field::length from number of characters to number of bytes
+
+  SYNOPSIS
+    create_field::create_length_to_internal_length()
+  
+  DESCRIPTION
+    Convert create_field::length from number of characters to number of bytes,
+    save original value in chars_length.
+*/
+
 void create_field::create_length_to_internal_length(void)
 {
+  chars_length= length;
   switch (sql_type) {
   case MYSQL_TYPE_TINY_BLOB:
   case MYSQL_TYPE_MEDIUM_BLOB:

sql/field.h

@@ -1180,7 +1180,15 @@ public:
   LEX_STRING comment;			// Comment for field
   Item	*def;				// Default value
   enum	enum_field_types sql_type;
+  /*
+    At various stages in execution this can be length of field in bytes or
+    max number of characters. 
+  */
   uint32 length;
+  /*
+    The value of 'length' before a call to create_length_to_internal_length
+  */
+  uint32 chars_length;
   uint decimals,flags,pack_length;
   Field::utype unireg_check;
   TYPELIB *interval;			// Which interval to use

sql/sql_table.cc

@@ -643,7 +643,7 @@ int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
 	  sql_field->charset=		(dup_field->charset ?
 					 dup_field->charset :
 					 create_info->default_table_charset);
-	  sql_field->length=		dup_field->length;
+	  sql_field->length=		dup_field->chars_length;
           sql_field->pack_length=	dup_field->pack_length;
 	  sql_field->create_length_to_internal_length();
 	  sql_field->decimals=		dup_field->decimals;