A fix and a test case for Bug#13134 "Length of VARCHAR() utf8

column is increasing when table is recreated with PS/SP":
make use of create_field::char_length more consistent in the code.
Reinit create_field::length from create_field::char_length
for every execution of a prepared statement (actually fixes the 
bug).

mysql-test/r/ps.result

@@ -733,3 +733,20 @@ count(*)
 5
 deallocate prepare stmt;
 drop table t1;
+drop table if exists t1;
+Warnings:
+Note	1051	Unknown table 't1'
+prepare stmt from 'create table t1 (a varchar(10) character set utf8)';
+execute stmt;
+insert into t1 (a) values (repeat('a', 20));
+select length(a) from t1;
+length(a)
+10
+drop table t1;
+execute stmt;
+insert into t1 (a) values (repeat('a', 20));
+select length(a) from t1;
+length(a)
+10
+drop table t1;
+deallocate prepare stmt;

mysql-test/t/ps.test

@@ -763,5 +763,27 @@ execute stmt using @like;
 deallocate prepare stmt;
 drop table t1;
 
-# End of 4.1 tests
 
+#
+# Bug#13134 "Length of VARCHAR() utf8 column is increasing when table is
+# recreated with PS/SP"
+#
+
+drop table if exists t1;
+prepare stmt from 'create table t1 (a varchar(10) character set utf8)';
+execute stmt;
+--disable_warnings
+insert into t1 (a) values (repeat('a', 20));
+--enable_warnings
+select length(a) from t1;
+drop table t1;
+execute stmt;
+--disable_warnings
+insert into t1 (a) values (repeat('a', 20));
+--enable_warnings
+# Check that the data is truncated to the same length
+select length(a) from t1;
+drop table t1;
+deallocate prepare stmt;
+
+# End of 4.1 tests

sql/field.cc

@@ -6516,13 +6516,11 @@ bool Field_num::eq_def(Field *field)
     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.
+    Convert create_field::length from number of characters to number of bytes.
 */
 
 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:
@@ -6775,6 +6773,7 @@ create_field::create_field(Field *old_field,Field *orig_field)
       break;
   }
 
+  char_length= length;
   decimals= old_field->decimals();
   if (sql_type == FIELD_TYPE_STRING)
   {

sql/field.h

@@ -1188,7 +1188,7 @@ public:
   /*
     The value of 'length' before a call to create_length_to_internal_length
   */
-  uint32 chars_length;
+  uint32 char_length;
   uint decimals,flags,pack_length;
   Field::utype unireg_check;
   TYPELIB *interval;			// Which interval to use

sql/sql_parse.cc

@@ -4480,6 +4480,7 @@ bool add_field_to_list(THD *thd, char *field_name, enum_field_types type,
 						  NOT_FIXED_DEC-1) : 0;
   new_field->sql_type=type;
   new_field->length=0;
+  new_field->char_length= 0;
   new_field->change=change;
   new_field->interval=0;
   new_field->pack_length=0;
@@ -4750,6 +4751,7 @@ bool add_field_to_list(THD *thd, char *field_name, enum_field_types type,
 					    FIELD_TYPE_STRING :
 					    new_field->sql_type,
 					    new_field->length);
+  new_field->char_length= new_field->length;
   lex->create_list.push_back(new_field);
   lex->last_field=new_field;
   DBUG_RETURN(0);

sql/sql_table.cc

@@ -488,6 +488,12 @@ int mysql_prepare_table(THD *thd, HA_CREATE_INFO *create_info,
 
   for (field_no=0; (sql_field=it++) ; field_no++)
   {
+    /*
+      Initialize length from its original value (number of characters),
+      which was set in the parser. This is necessary if we're
+      executing a prepared statement for the second time.
+    */
+    sql_field->length= sql_field->char_length;
     if (!sql_field->charset)
       sql_field->charset= create_info->default_table_charset;
     /*
@@ -665,7 +671,7 @@ 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->chars_length;
+	  sql_field->length=		dup_field->char_length;
           sql_field->pack_length=	dup_field->pack_length;
 	  sql_field->create_length_to_internal_length();
 	  sql_field->decimals=		dup_field->decimals;