BUG#4788 - show create table provides incorrect statement.

Added code to adjust the field_length of user variables 
in dependence on the field type.
Aded new constants for numeric field widths.

include/mysql_com.h

@@ -136,6 +136,11 @@ enum enum_server_command
 struct st_vio;					/* Only C */
 typedef struct st_vio Vio;
 
+#define MAX_TINYINT_WIDTH       3       /* Max width for a TINY w.o. sign */
+#define MAX_SMALLINT_WIDTH      5       /* Max width for a SHORT w.o. sign */
+#define MAX_MEDIUMINT_WIDTH     8       /* Max width for a INT24 w.o. sign */
+#define MAX_INT_WIDTH           10      /* Max width for a LONG w.o. sign */
+#define MAX_BIGINT_WIDTH        20      /* Max width for a LONGLONG */
 #define MAX_CHAR_WIDTH		255	/* Max length for a CHAR colum */
 #define MAX_BLOB_WIDTH		8192	/* Default width for blob */
 

mysql-test/r/variables.result

@@ -452,3 +452,29 @@ set global log_warnings = @tstlw;
 show global variables like 'log_warnings';
 Variable_name	Value
 log_warnings	1
+create table t1 (
+c1 tinyint,
+c2 smallint,
+c3 mediumint,
+c4 int,
+c5 bigint);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c1` tinyint(4) default NULL,
+  `c2` smallint(6) default NULL,
+  `c3` mediumint(9) default NULL,
+  `c4` int(11) default NULL,
+  `c5` bigint(20) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+set @arg00= 8, @arg01= 8.8, @arg02= 'a string';
+create table t1 as select @arg00 as c1, @arg01 as c2, @arg02 as c3;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `c1` bigint(20) default NULL,
+  `c2` double default NULL,
+  `c3` longtext
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;

mysql-test/t/variables.test

@@ -335,3 +335,22 @@ show global variables like 'log_warnings';
 set global log_warnings = @tstlw;
 show global variables like 'log_warnings';
 
+#
+# BUG#4788 show create table provides incorrect statement
+#
+# What default width have numeric types?
+create table t1 (
+  c1 tinyint,
+  c2 smallint,
+  c3 mediumint,
+  c4 int,
+  c5 bigint);
+show create table t1;
+drop table t1;
+#
+# What types and widths have variables?
+set @arg00= 8, @arg01= 8.8, @arg02= 'a string';
+create table t1 as select @arg00 as c1, @arg01 as c2, @arg02 as c3;
+show create table t1;
+drop table t1;
+

sql/item_func.cc

@@ -2724,7 +2724,19 @@ void Item_func_get_user_var::fix_length_and_dec()
   error= get_var_with_binlog(thd, name, &var_entry);
 
   if (var_entry)
+  {
     collation.set(var_entry->collation);
+    switch (var_entry->type) {
+    case REAL_RESULT:
+      max_length= DBL_DIG + 8;
+    case INT_RESULT:
+      max_length= MAX_BIGINT_WIDTH;
+      break;
+    case STRING_RESULT:
+      max_length= MAX_BLOB_WIDTH;
+      break;
+    }
+  }
   else
     null_value= 1;
 

sql/sql_parse.cc

@@ -4208,23 +4208,23 @@ bool add_field_to_list(THD *thd, char *field_name, enum_field_types type,
 
   switch (type) {
   case FIELD_TYPE_TINY:
-    if (!length) new_field->length=3+sign_len;
+    if (!length) new_field->length=MAX_TINYINT_WIDTH+sign_len;
     allowed_type_modifier= AUTO_INCREMENT_FLAG;
     break;
   case FIELD_TYPE_SHORT:
-    if (!length) new_field->length=5+sign_len;
+    if (!length) new_field->length=MAX_SMALLINT_WIDTH+sign_len;
     allowed_type_modifier= AUTO_INCREMENT_FLAG;
     break;
   case FIELD_TYPE_INT24:
-    if (!length) new_field->length=8+sign_len;
+    if (!length) new_field->length=MAX_MEDIUMINT_WIDTH+sign_len;
     allowed_type_modifier= AUTO_INCREMENT_FLAG;
     break;
   case FIELD_TYPE_LONG:
-    if (!length) new_field->length=10+sign_len;
+    if (!length) new_field->length=MAX_INT_WIDTH+sign_len;
     allowed_type_modifier= AUTO_INCREMENT_FLAG;
     break;
   case FIELD_TYPE_LONGLONG:
-    if (!length) new_field->length=20;
+    if (!length) new_field->length=MAX_BIGINT_WIDTH;
     allowed_type_modifier= AUTO_INCREMENT_FLAG;
     break;
   case FIELD_TYPE_NULL: